GARP Part 2, the Great Axle Reconstruction Project

Intro

In Part 1, I described the events leading to disassembly and repair of the front axle.

Part 2 describes the reassembly process.

Hubs and Spindles

Following on from Part 1 which was initiated by a front end vibration, I have now cleaned up the spindles, removed the diff inner oil seals and checked the bearings for fit on the reground spindles. The shells are a tight fit, or rather, they need accuracy in location or they will jam sideways. Once correctly located the bearings slide and rotate very smoothly. Of course, once the bearings are tightened up the shells shouldn't move or rotate on the spindles anyway.

I removed the rear hub oil seals, using an inside gear puller pressing on a steel bar placed across the hub, but before replacing them, I tried the hubs and bearings on the reground spindles, temporarily reattached to the steering knuckles. This is to ensure they can be correctly assembled without jamming when the hub is offered up to the spindles. Had the inner bearing jammed on the spindle, it would have damaged the new oil seal when the hub was removed.

If the bearings are jamming, smoothing the spindle with some fine emery cloth and careful cleaning with WD40 will help, as will a smear of oil on the bearing surfaces. Older bearings will fit slightly easier than brand new ones.

If the hub and bearings can be successfully located on the spindle without jamming, a new oil seal can be pressed into the rear of the hub, by gently tapping around the edge with a heavy hammer until it's flush with the hub casing. Don't knock dirt from the back of the hub into the bearings.

 

Oil seal inserted into the rear of the hub

Diff Carrier Rebuilding

Refer to Section 4 of the Dana 70 Maintenance Manual (available here) and the Carrier section of the Dana 60 Maintenance Manual (available here) for advice on how to do this. The front axle of an Oka is actually a Dana 60 while the rear is a Dana 70, but there are many similarities and the techniques in these manuals are relevant to both types. In fact there's a host of useful documents available from the Dana website here.

After removing the diff centre carrier, I unbolted and removed the ring gear, knocked the roll pin through and removed the cross shaft and differential gears.

Because it's a heavy item and would be seriously damaged if it fell on the concrete floor, I inserted a sturdy cable through the carrier and tied it to a roof beam so that if it slipped out of the vice whilst being worked on, it would swing clear and only hit me, not the hard concrete.

Removing the ring bolts was easier than anticipated since they should have been torqued to 130 ft-lbs (176 Nm) and Loctited too. I left four of the bolts partly in place and tapped them with a hammer to free up the ring gear, which wasn't very tight anyway. I moved the carrier from the vice to the workbench and then removed the last 4 bolts whilst holding the ring away from any hard objects. I didn't want to have to replace that as well, since ring gears only come as matched pairs with the pinion, which would have made it a much more difficult (and expensive) job.

The Ring Gear being removed

The bearing cups came away when removing the diff centre, so I put old socks over each of the bearings to protect them while this work was being done.

I tapped out the roll pin using a length of 5mm steel rod, and the cross shaft then slid out of the carrier.

Removing the differential gears looked difficult since they remained meshed together, but by turning a side gear, the spider gears simply walked themselves around to the opening in the diff and fell out. All 4 gears are seated on thrust washers which might be stuck to the carrier by oily suction.

I smoothed the rusted and pitted surfaces of the ring gear with fine emery paper and WD40 and cleaned them off with Brake Cleaner fluid.

The broken gear wheel will end up in my Museum of Broken Car Parts which is becoming quite extensive.

 

The diff in pieces ready for reassembly

The Differential Gear Set

A close up of the offending tooth

Diff Oil Seals

Removal of the Inner Seals

To remove the inner diff oil seals I built a pusher rod made of a metre of 12mm tapped rod with a large steel washer, just the diameter of the rear guide section of the seal, bolted to the other end. A few whacks with a heavy hammer and the seals popped out into the diff chamber. Other people have used a large socket and several extension bars to achieve the same result, but I didn't have the right size socket (or sufficient extension bars). The bar needs to be at least 1 metre long to remove the LHS seal.

This bar, with a sock tied over the washer, also makes a useful tool for cleaning out the oily/muddy sludge from the axle tubes.

The pusher for removing the inner seals and cleaning out the axle tubes

Installing the Inner Seals

To insert the seals I used a modified 40 mm high pressure water fitting, which just fits inside the seal body, to avoid damaging the plastic parts of the seal with a hammer. The fitting will need to be cut down to about 50 mm long to allow a hammer to be swung inside the diff housing. I drilled and fitted a long bolt to the side of the plastic fitting as a handle, to keep my thumbs well clear of the hammer. A suitable socket might also work. Alternatively a pusher tool could be made up as described in the Dana 60 manual. Any rust or corrosion around the seal location should first be removed and the surfaces smoothed down.

The old seals had silicon gasket sealant smeared around their outer surfaces before insertion, presumably to keep water away from the metal surfaces and prevent premature rusting. Seems like a good idea, as does greasing the seals and guide inner surfaces to help the splined drive shafts find their location.

However, sealant on the seal casing also makes them slippery and more difficult to keep centred as they are inserted. It takes a quite a lot of effort in a confined space to insert the seals straight, since they are a tight fit, and I had to remove and reinsert one of them a couple of times to avoid fitting it crookedly. A pusher tool would certainly be more effective.

Mind the pinion gear, bearing seats and thumbs as you are wielding the hammer, damage to those would be expensive and/or painful.

Clean out all the resulting muck from the diff housing.

A modified 40 mm high pressure water fitting would fit inside the body of the seal

Reassembling the Diff Carrier

Before reassembling the diff centre, ensure that the ring bolts and tapped holes in the ring gear are thoroughly cleaned and free of old Loctite.

Before the ring is refitted, the new gear set must be installed, with their thrust washers, and the cross shaft and roll pin inserted. Oil all the parts well before assembly and check for smooth rotation.

Installing the Differential Gears

You'll need about 15 fingers to hold the 4 gears and their thrust washers in the right place but it's not too difficult. Insert the side gears first on their washers, with the carrier horizontal so they can't fall out. Then insert both spider gears exactly 180º apart from either side of the carrier and walk them into the carrier case by turning both side gears in the same direction. If they are not exactly 180º apart on the side gears the cross shaft holes won't line up. I found it easier to slide the saucer shaped thrust washers in behind the spider gears after the gears were in place.

Gears reinstalled in the carrier

Once all the gears are in place, centre the the spider gear washers with a finger and insert the cross shaft with the roll pin holes roughly in line. Use a thin bar to turn the cross shaft until the roll pin holes line up and drive in the roll pin. The differential gears are now complete, assuming they all turn smoothly.

 

Driving the Roll Pin home to complete the assembly

Installing the Ring Gear

The ring gear should be replaced in its original orientation (not sure why, it doesn't seem to be a balanced item, but that's what the manual says) and this can be determined from the imprint markings on the carrier made by the ring. There is a cut out on one side of the ring, presumably for oil flow, which will show up as a shadow on the carrier. I also took photos of the stamped markings to confirm it's location.

The manual also suggests replacing the 12 ring gear bolts, but they are very high tensile bolts (SAE Grade 8, equivalent to metric class 10.9) and if they are in good condition and not stretched or worn, the originals could be reused. On a rear diff, which is subject to a far higher and continuous load, I would certainly replace the bolts.

[BTW, if you are excited by such things, there is a very good Australian document on bolts (and fasteners in general) available for download from the James Glen Company here, or view an on-line version here].

The ring bolts need to be tightened alternately to 130 ft-lbs (176 Nm) and Loctited. A tight fitting socket is required (hex, not multi-point is preferred to avoid rounding the corners) and the carrier needs to be securely held in a large vice, preferably tied to something substantial to catch it if it breaks loose. Vice jaws have been known to snap off. Protect the exposed bearings while doing this.

My torque wrench only goes up to 110 ft-lbs so I tightened the bolts alternately to 110 ft-lbs and then used a longer bar to turn them all a fraction of a turn more, about 25º to 30º (1/12th of a turn max.). I reasoned that this would increase the torque to around 130 ft-lbs. Don't forget the Loctite and ensure you haven't missed out tightening any bolts, 12 is a lot to remember.

Reinstalling the Diff Carrier

Fully fitted with gears, the carrier is a bit of a handful to manage under the vehicle. It has to be manoeuvred around the tie rod, the bearing cups have to be fitted and held in place and the whole assembly inserted straight and level into the housing so that the pinion engages with the ring gear and the bearing cups locate correctly in their slots. And it's heavy and makes your arms ache.

The bearing cups had previously been rotating in their housing and caused a burn mark so I applied some Loctite 641 (bearing retaining compound) to the housing and bearing caps to stop them rotating.

The differential installed in the carrier

 

It took me a couple of goes before I could locate the carrier properly, but I had the bolts and bearing caps ready to go so that when finally it slipped into place I could whip in a bolt to hold it there before it all fell out again. Had the diff carrier been a press fit requiring a diff spreader to remove it, I doubt that it could have been replaced in situ and the axle would have had to be removed first.

Once I had recovered my strength and confirmed that the gears all rotated correctly, I Loctited the bearing cap bolts and torqued them up to 80 ft-lbs. The bearing caps should be replaced in the same orientation as previously. They have stamped markings on to aid identification.

Fitting the Drive Shafts

Once the diff is in and working correctly (although I don't see how it couldn't work as it's a very simple but clever mechanism), the drive shafts can be installed.

I had already cleaned them up, checked the UJ's and replaced the oil seals. I was surprised to find the short shaft UJ had a grease nipple, which worked. It must have been hidden under years of dirt and sludge and in 5 years I had never noticed it. Presumably this UJ, or maybe the complete shaft, had been replaced at some stage as the inner splines were also much less worn than the long shaft, which had no grease nipple. Fortunately there was little play in either UJ.

When reinstalling the drive shafts I wanted to avoid the splined end from collecting dirt, as it was pushed along the axle tube, and injecting it into the diff housing. So I placed a thin plastic strip in the axle tube and slid the drive shaft along that and straight into the diff. The plastic strip was actually the cap from a length of Clipsal rectangular electrical conduit and acted like a thin "V" shape for the splined shaft to slide along. When the shaft had entered the diff housing but not fully engaged with the side gear, I pulled the plastic strip out of the axle tube and pushed the drive shaft home, all nice and clean.

Using a length of plastic strip to keep the drive shaft out of the dirt. The oil seal has also been replaced

Refitting the Spindle

Before refitting the spindles, I levered out the old oil seals (which had broken in 2 anyway), flushed out and re-greased the needle bearings and tapped new oil seals into the back of the spindles.

Clean and grease the rear of the spindles around the needle bearing seal since the drive shaft oil seal engages that surface.

Needle bearings greased and new oil seal fitted into spindle

Strangely, I couldn't recall the order in which the spindle, brake calliper plate and stone guard came off, so I thought "simple, I'll look it up in the manual".

Wrong. There are pictures of the axle, spindle and hub arrangements and pictures of the brake rotor and calliper, but none showing both. Eventually I deduced that the spindle is attached direct to the steering knuckle with the brake calliper plate on next and the stone guard on last. It didn't look right, due to the cranked angle of the calliper plate and stone guard, but it was logical when I thought about it.

Loctite the spindle fixing nuts and tighten them to 65 ft-lbs. Once the hub is in place you can't reach them anymore.

Refitting the Spindle, drivers side

Grease the rear oil seal bearing surface and clean out the spindle nut threads.

When fitting the hub to the spindle, have the greased up outer bearing and the hex spindle nut ready to go. Otherwise, when you fit the hub with only the rear bearing in place the hub might slip down the spindle when you let go.

I was tempted to put bearing retaining compound on the bearing cup surfaces to prevent the original problem of the bearing cups rotating on the spindles, but there is so much grease around that I doubt that the retaining compound could do it's job effectively. With rebuilt and reground spindles it shouldn't be necessary anyway.

The spindle nuts should be tightened to 50 ft-lbs, spun a few times to seat the bearings and circulate the grease and then backed off about 45º before fitting the lock washer and outer lock nut. Pre-loading is essential for tapered roller bearings so they share the load equally. If there is any free movement, they are too loose. On the road I check the temperature of the hubs frequently to ensure they are not getting too hot. Warm is OK due to the brake heat, but if one is appreciably hotter than the others, something is wrong.

[There are some very useful tech notes on bearing problems and installation at the Timken site hereand here].

Fitting the lock washers can be a tricky task. Bend 2 tabs in towards the bearing, being careful not to go too far or you can damage the bearing cage. I used a rod formed from the tapered end cut off a tent peg to do this. Bending 2 tabs outwards on to the lock nut is even more difficult. I made a small tool using another tent pen with a sharp bend on one end (more than 90º so it won't slip off) and threaded the other end. Using a breaker bar with a hole it it, I slid the tool in behind the tabs and levered against a nut fitted on the threaded end. Once the tab has bent slightly, I used a square shank screwdriver to lever them flat by twisting it with a wrench on the shank.

[In the US, there are more sophisticated (but expensive) locking devices described here and here].

Epilogue

The rest of the rebuilding process (free wheeling hubs, tie rod ends, steering damper, brakes, wheels, diff cover/oil etc.) should be fairly straight forward, but as with any major project, check if there are any bits left over and check that everything is reconnected, tightened, greased or refilled.

On it's first test run, there was no evidence of the original vibration which kicked off the whole axle reconstruction program in the first place, and the steering seemed a lot smoother, although there's no logical reason for that other than the greased joints. I ran the Oka in 4wd for a while, but with the hubs unlocked, to allow oil to circulate through the diff components before any load is applied to it.

This has been quite a long and complex rebuilding process and ironically, there will be almost nothing to show for it at the end, except peace of mind.

However, it is not difficult or mechanically challenging or even very expensive, there's just a lot of it.

Vibrations from the Front Axle - Part 1 of GARP, The Great Axle Reconstruction Project

Over the past few months our Oka developed an occasional but worrying vibration at 60-70 km/h from what appears to be the front axle/wheel area, possibly from the passengers side. Braking or turning or de-clutching didn't seem to affect it and it was there in 4wd and 2wd. 


At first I thought it was just knobbly tyres on a rough road surface (that's what it sounds like), or the brake callipers (see this article, which is relevant to Oka brakes), but I thought I had fixed any calliper/pad rattles and looseness. Then I thought maybe a wheel bearing shell might be jamming occasionally and rotating on the spindle, but why only at one speed? Investigating that possibility is a rotten job, with freewheeling hubs and brake callipers to remove, lock washers, messy grease etc. and anyway I had checked/greased the bearings last year and recently had the wheels balanced.

"Tim" on the Oka Owners Group website suggested that the vibration might be caused by a worn steering damper. I haven't investigated that yet, since everything is now in pieces, but it is a possibility, although I don't quite understand how it could occur or why turning the steering wheel didn't affect it. I had considered ignoring the problem completely and just turning up the radio, but after checking the steering rods and swivels, springs and shockers, and any part of the bodywork which could have been vibrating in the wind, I bit the bullet and took the wheel hub assembly to pieces.

Pic 1. The groove and ridge ringed on the spindle shaft. (Click to enlarge)

It only took an hour or so to get to the heart of the problem, the outer bearing shell had indeed been rotating on the spindle and worn a groove (about 0.5 mm deep), so that the bearing was a fairly loose fit on the shaft. A ridge had also developed which prevented it from sliding freely, and this would affect the bearing pre-load adjustment as well. See ringed area on Pic 1.

What to do about it was the next question. If we were in the US, a replacement spindle for a Dana 60 axle would be easy to find (and cost around $US100-150), but in Oz, from Oka the price was out of this world ($600, each).

So I investigated a repair process. I found a company in Adelaide (Adelaide Grinding) that would deposit a coating of metal on the shaft (by replating or metal spraying) and then regrind the bearing surfaces to their original dimensions. Since I wanted to do this only once, I also had the inner bearing surface treated at the same time, even though it wasn't as badly worn. Even better, the total cost was less than a quarter of the new spindle price.

While I was at it, I took the other spindle off and, not surprisingly, it was in a similar state of disrepair so I had that repaired as well.

Pic 2. The repaired spindle. Bearings are a good tight slide fit on the reground shafts.

I will also replace the oil seals at the rear of the spindles and the seals on the drive shafts to keep water out of the bearings. The needle roller bearings which centre the drive shaft were very gunged up but not badly worn, so a good clean out and regrease is all that is necessary.

The 6 nuts holding the brake calliper and spindle on to the steering knuckle weren't as tight as I was expecting, considering that they support the whole weight of the vehicle, plus traction and braking loads as well, so I will Loctite them and torque them to 60 to 70 ft-lbs. The torque setting for Dana 60 Spindle nuts is 65 ft-lbs (88 Nm) and I assume it would be the same for Dana 70 rear axles.

I did consider rotating the spindles so that the previously worn section was now having a rest and a new section could take up the load. However, that plan came to nought when I discovered that the spindle bolt holes are not symmetrical and the spindle will only fit one-way. It is possible to interchange the left and right side spindles however, which might have a marginal benefit.

The Low Point Approaches...

While the hubs were off being repaired, I took the opportunity to change the front diff oil.

So I loosened the diff cover bolts to let the oil out (for there are no drain plugs on these axles) and heard a "clink" as something dropped into the tray. Rather than dirty my fingers, I got my magnetic wand out and stirred it around in the dirty oil. When I removed it there was part of a gear tooth attached to the end.

My heart sank as I knew what that would mean, and sure enough, when I removed the cover and turned the inner gears around there was one with part of its tooth missing.

Pic 3. Toothache in the differential.

Had there been a drain plug I would never have noticed the missing tooth, but since I now knew about it, it simply couldn't be ignored. From a pragmatic perspective, there would never be a better opportunity to repair the diff, as removing it was only 4 bolts away, since the hubs, wheels, brakes and drive shafts had already been removed.

This was also the unexpected opportunity I had been waiting for to replace the inner axle oil seals which are only accessible when the diff is removed. Muddy water from Kimberley creek crossings had got into the diff housing past the worn seals and laid at the bottom of the housing. This had caused surface rusting and pitting on some of the crown wheel teeth and bolts, since the front diff is stationary for much of the time. Mine site seals are available to block off the openings to the axles tubes, but the advice I received is that they tend to trap water in the tubes leading to worse corrosion problems, and it's better to allow them to drain open to the atmosphere.

Removing the diff was surprisingly easy and after freeing the 4 bearing cap bolts, it just about fell out, or would have done, except for the steering tie rod which crosses right in front of the diff cover. This tie rod can't be easily removed since it hits the bottom of the springs before the tie rod ends can be lifted free from the steering knuckles. Luckily, after a bit of manoeuvring I managed to turn the diff carrier assembly on its side and slide it out under the tie rod. If you've already loosened one or both tie rod ends, it would probably help to clamp the rod up as high as possible to keep it out of the way. I just hope putting it back will be as easy.

So, buoyed with the negligible enthusiasm which stems from having reluctantly removed the diff, I went on the hunt for replacement gears, and once again in the US they are easy to come by, but not so easy in Oz. They are available from a few auto parts companies specialising in American vehicles, (eg here and here) but to be sure I got Oka compatible components, I acquired a second hand set from Paul Nott at East Coast Oka in Melbourne (which turned out to be a lot less worn than my original set). With some replacement oil seals on the way from Oka in Perth I am now able to start GARP, the Great Axle Reconstruction Project.

GARP Part 2 documents the axle reassembly phase from this low point to being ready to roll.

Don't you just love it when the manuals say "To reassemble, simply reverse the disassembly procedure"?

Snake in Well 46 on the Canning Stock Route

As we moved down the Canning Stock Route (CSR) in 2007, we started getting warning messages on the bush telegraph about a snake in Well 46.

We knew that Well 46 was one of the few wells with potable water in it, so we grew a little apprehensive as we approached.

The bush telegraph works surprisingly well in many outback locations as well as the CSR and usually involves hand written notes and messages placed in glass jars or tins, or Texta messages on white-boards, located near visitors books or obvious sign posts at key locations. We met almost no one on the CSR so this method of communications is valuable.

[Some of the messages go back many years and form a good historical log of the area. A good example of this is the visitors book at Veevers Meteorite Crater, off the Gary Highway, which still has hand written notes from 1975 in it, by the people who discovered the crater (see Gary Highway)].

We first heard of the snake in Well 46 from this anxious note left at Well 49 a couple of months earlier.

To make matters worse, this snake (a king brown and potentially deadly), had apparently been caught by the tail in the heavy hinged covers of the well, put in place to prevent animals falling in and polluting the water. The story goes that some previous visitors had opened a cover on the well, saw the snake slithering in or out and dropped the cover in panic, catching the snake's tail between the halves of the covers.

Later visitors, concerned about leaving the snake in that situation (ants were eating its trapped tail), tentatively lifted one cover and released the snake which fell into the water, with about 200 mm of squashed tail.

So it was quite likely to be a bit angry and aggressive.

[Note: The Canning Stock Route is a very lonely place and very remote from any medical assistance, so snake bite is something to be avoided at all costs. Well 46 is at least 250 km (and a couple of days hard drive north at 15-20 km/h) over difficult sand dunes from the nearest help at Billiluna, plus another 200 km or so to the nearest hospital at Halls Creek. You would probably not survive a severe snake bite in that time. Your best bet would be an RFDS emergency call on your HF radio or Sat phone for a doctor with a polyvalent antivenin to be waiting at Billiluna airstrip.

If a similar event happened further south, there is an airstrip and potential help at Kunawaritji near Well 33, at Parnngurr in the Rudall River National Park and further south still, at Granite Peak Station.

Even these places are very remote from major towns or medical facilities and it would be very wise to know First Aid for snake bite before venturing this far away from help. Take a copy of one of these with you: Snake Bite First Aid 1, or Snake Bite Identification and Management, Snake Bite Treatment, and for good measure one of these: CPR Chart. If these sites fail, Google Snake Bite Treatment for Australian snake bite sites.

For more detailed info on snake bite treatment refer to the Discussion Notes here.

So we approached the well carefully...

...just in case...

... and now there appears to be 2 snakes, according to this note.

So instead of opening the covers by hand, I carefully threaded a rope through the handles and opened the cover remotely...

... and yes, there was one snake (maybe 2), curled up under the timber frame, above the water line.

It seemed to be quiet and undisturbed and we still needed some water so we gently lowered the bucket into the water and pulled it up.

The snake didn't move as we repeated this noisy exercise (it's a very heavy bucket) a few times, until we had what we needed.

Pumping water out of the bucket.

However, there was other wildlife around too.

As we watched a beautiful goanna slid out from under the frame to sun itself. It watched us as we took its photo.

A beautiful sand goanna, probably Varanus gouldii.

The downside to this visit was that we left a partially filled bucket of water on the well while we had lunch. Sadly, within 10 minutes, several finches had gone down to the water to drink and fell in and six had drowned. We managed to revive one of them.

Finches risking their lives for a drink.

We wrote a note on the white board requesting other visitors NOT to leave water in buckets for finches since they seem incapable of getting out, even if a log is left in the bucket for them to crawl up. It's better to pour water down the cattle troughs for them, where it will remain shallow.

Gulvida Soak, Well 50 on the CSR

At the top end of the Canning Stock Route, near Well 50 is a small but interesting gorge on an unnamed water course (Gulvida Creek?), but what is probably a remote branch of the Sturt Creek.

A short walk along the a creek leads to Gulvida Soak, a well hidden but important water hole in a cave at the back of a small gorge.

[Note Gulvida is variously spelled as "Culvida", "Guldiva" or "Culdiva". "Gulvida" is used on official Geoscience Australia NatMaps while Hema/WestPrint use "Culvida", the others appear to be wrong.]

Travels in this area, and maybe Gulvida Soak on the Sturt Creek, were described by Michael Terry in his book Across unknown Australia, published in 1925. Terry and companion Richard "Dick" Yockney had run out of benzine and nearly died of thirst when they stumbled upon a soak which saved their lives. It was in a creek very remiscent of, and in the same general area, as the Gulvida Soak creek, about 47 km (30 miles) west of Lake Gregory.

At a time when there were no roads, Terry was one of the first people to cross Australia by motor vehicle, and the book describes his travels from Winton to Broome in 1923. Prior to Terry's travels, all major outback journeys had been by camel train or on horseback.

Michael Terry and his 1923 transport...

... and our 2007 equivalent.

An interesting summary of Michael Terry's travels, by Ron and Viv Moon, can be found here, and a Wikipedia entry here.

 

Our GPS track (in blue) to Gulvida Gorge.

To access the gorge you need to drive about 4 km south west from Well 50 along a fairly obvious track to the top of the creek, scramble down and walk along the dry winding creek bed for about 1 km.

The Gulvida Soak marked on the maps is presumably an ephemeral water hole/billabong in the creek bed, not the gorge and cave we went to, which is further on.

Looking back at the "car park" on the top of the creek.

It's a good idea to keep a mental picture of where your car is when setting out on a walk in a remote area, to orient your self for the return. Or take a GPS with you. And if you're in groups, hand-held CB radios are valuable.

A 1 km walk along a dry creek bed along leads to small gorge off to the left (south) of the creek which contains a hidden and well protected water hole. On the walls of the gorge are aboriginal carvings which demonstrate the importance of this water supply to the aboriginal people.

The gorge is just around the corner on the left...

... behind the bush.

The gorge is quite easy to find, since its opening will be advertised by clouds of noisy zebra finches as they fly in and out of the cave and rest in the surrounding bushes.

At the back of the gorge, almost invisible in the bright sunlight, is a cave with a deep water pool in the darkened interior.

Depending on the seasons, there may also be small soaks in the creek bed, presumably dug out by kangaroos, which will also buzz with zebra finches.

But the most interesting part of the gorge is the gallery of aboriginal carvings on the gorge wall.

Then it's a pleasant walk back to the car. It's hot and we took plenty of water, but we are not wearing fly-hats so there can't have been too many pesky creatures about either.

And finally, here is a video of Gulvida Gorge taken by Michael Olsen in 2009, when there was plenty of water in the creek, unlike our visit in 2007 when it was bone dry.

Gulvida Soak near Well 50 - Canning Stock Route from Michael Olsen on Vimeo.

Michael has posted several other interesting videos here. Thank you Michael, I would thank you personally but I don't have your contact details. If you read this please leave a message by clicking the mail icon below.

Secret Airbase Revealed - Corunna Downs

Some of the more interesting aspects of travel in the north of Australia are the frequent encounters with WW11 sites and memorabilia which have made an indelible impression on the history and landscape of that part of the country. One story that captured my imagination many years ago was that of a secret airbase that was never discovered by the enemy and whose whereabouts, or even existence, were not disclosed until after the war.

In 1942, an airbase was built in the north west of WA, beyond range of enemy aircraft, and intended as a strike base against Japanese occupation forces in Indonesia and Borneo. The Japanese suspected the existence of a base due to the frequent raids launched from that area, but although they searched for it many times, they never found it. Distance, and the clever use of camouflage helped maintain its secrets.

However it did exist, and it was used successfully from May 1943 to 1945 by RAAF No 25 Squadron and the USAF's 380th Air Wing, both equipped with B-24 Liberator heavy bombers. In fact the airbase still exists today and although abandoned since 1945, sufficient relics remain to make a visit to the area a very interesting historical diversion.

The picturesque road from Marble Bar to Corunna Downs

Its exact location is no longer a secret and the airbase can be found about 36 km due south of Marble Bar on Corunna Downs Station. It's reasonably accessible if you have a good map and a GPS.

Take the Corunna Downs Road (also called Salgash Road) south from of Marble Bar for about 30 kms until a turning on the right, marked by an oil drum, about 500 m past the Camel Creek crossing. Follow this track for about 750 m and turn left, just over another small creek. It's then a further 6 kms along a fairly straight track to the airfield.

If you miss the first turn you will end up at Corunna Downs homestead.

The tracks are dry weather roads and are navigable by 2WD vehicles, although 4WD's are preferable.

The Corunna Downs airbase from Ironstone Hill

On our first visit in 2002, without the benefit of a GPS we actually reached the airfield perimeter road without realising where we were, and turned back assuming we had missed it completely. We surmised, correctly, that the secret airbase was going to retain its secrets a bit longer.

On our second trip in 2007, forearmed with better knowledge and equipment, we located the airfield quite easily and spent 2 days there soaking up the atmosphere and fossicking amongst the rusting memorabilia.

A good way to get your bearings before actually going there is to visit the airbase on Google Earth at 21°25'53.79"S, 119°46'56.73"E, where all its features can be clearly seen.

A visit to the Comet Gold Mine just outside Marble Bar will also provide useful background information on the airfield from their displays of maps, photos and descriptions of the installations.

The main runway at Corunna Downs

Although the airbase is on Corunna Downs station, on 10th April 2007, the Corunna Downs Airbase was granted a permanent entry on the Register of Heritage Places, maintained by the Heritage Council of WA (Ref 2).

The entry reads in part "Corunna Downs Wartime Airbase is a rare example in Western Australia of a strategic Royal Australian Air Force (RAAF) base established specifically as a heavy bomber base and is significant as a reminder of the way of life for the forces personnel who were based there".

The airfield is quite extensive, comprising 2 main runways of 7000 ft and 5000 ft plus 20 aircraft revetments and several km of taxi ways. A 3rd 6000 ft runway was planned but never built. These features are still in remarkably good condition today and although the buildings have all been removed, there are a large number of concrete plinths, supply dumps and earthworks to explore, forage through, or wonder about.

Strange relics of the airbase

There are piles of bomb holders, arming spinners, ammunition clips and many other items the purpose of which is a mystery.

Bomb spinners

When foraging amongst the strange metal objects left behind, you might come across live ammunition. We didn't, but others have, and it should be left well alone as after 65 years, live rounds could be unstable and dangerous. Also be on the look out for snakes and scorpions which apparently tormented the troops stationed there.

Ammo clips by the gazillion

Bomb clamps

And when you're all foraged out, the surrounding scenery of rolling green hills and creek lines is quite spectacular. It's worth camping there for a night to become immersed in the feeling for what wartime in the outback must have been like. It was so hot in summer that showers were banned from 9 am to 9 pm because the water was scolding hot and they were plagued by biting march flies.

Wartime relics now covered by spinifex

Working in the heat, dust and flies of outback Australia must have been very difficult for the crews stationed there, particularly for the American forces, a long way from home, fighting an unseen enemy, in a desolate and lonely part of a foreign country. I sometimes think we don't fully appreciate what the American forces did in the defence of Australia.

[A stark reminder of the realities of war is the site of a crashed Liberator near Mandorah on the Cox Peninsular, west of Darwin, in which 6 young American airmen tragically died in a training exercise defending our northern approaches. That site is also well worth a visit for a sober reflection on their contribution to our safety].

Imagining the wartime pilots about to take off

The main runway at Corunna Downs is 7000 ft (2.13 km) long, and was necessary to allow heavily loaded bombers to take off safely (although not easily) in the high temperatures of the region. In an article entitled "Why is a Runway 7000 Ft Long?", Ron Alcock describes a scary take off from Corunna Downs in 1945 in a Liberator carrying 8 x 250 lb bombs plus 6000 lbs of additional fuel (its maximum load) for a long distance raid.

"At 119 m.p.h., the end of the bitumen runway disappeared under the nose, so did the laterite over-run, so did some of the spinifex country before (with great relief) we were airborne". Later he says "Forty paces beyond the runway’s end plus the 100 yard over-run, we found a recently mangled ‘yacca stick’ clump and my wandering mind visualized what a fiery crater there could have been, just past that yacca". "So there was a perfectly good reason for a runway being 7000 feet long".

If you park in one of the aircraft revetments it's easy to image the wartime scene with aircraft coming and going and men sweating over bombs, ammunition boxes and ground equipment. You can almost hear the rumble of aircraft lumbering into the skies on their missions, some of which were regrettably only one way.

70+ years on, despite advances in transport and communications, Corunna Downs is still in a very remote part of the country although it's now much easier to access. And along the way we found Marble Bar and the rolling hills of the surrounding countryside to be surprisingly pleasant and attractive, and not at all like the images conjured up by its reputation as Australia's hottest town.

So even if you are not enamoured of wartime stories, and you find WW11 installations a bit boring, just think of the conditions those men and women endured and why they were there, and enjoy the scenery along the way.