The steering column in an Oka comprises a telescopic splined shaft and 2 universal joints connecting the steering wheel to the power steering box.
The Oka manuals have good breakdown diagrams (Section 8 of the Parts Manual) and removal descriptions (Section 3 of the Service Manual).
The shaft removed from the Oka. The lower UJ is still on the Steering Box.
If the column rattles over rough roads, it could be the UJ's which are worn or loose, or the sliding joint. The plastic ring inside the column indicator switch assembly can also rattle but that's unlikely to be the real cause.
You can check column wear by holding the lower UJ in your right hand under front of the drivers floor (without the engine running), whilst moving the steering wheel with the left hand. If there's any perceptible movement or clonking, something needs to be done.
If it's the top UJ, the only solution is a new column assembly as the top UJ is part of the shaft body. If it's the lower UJ, that can be replaced independently, but both UJ's will probably be worn by a similar amount. They don't have grease nipples. Note that there are two sizes of lower UJ, one for the original Kirby Bishop steering box and a larger one for the TRW box.
If the sliding joint rattles, it can be fixed fairly simply and at low cost. The shaft doesn't need to be replaced, or even removed.
Although it's a sliding, splined shaft, it spends most of its time working in the same spot and when the paint has worn off the piston shaft, it becomes loose and rattles annoyingly on any rough surface, even though it is still quite safe to use.
I have fixed my rattle by clamping an old urethane spring bush to the piston shaft and then securing that to the main body of the column using a piece of PVC pipe and 2 hose clips. I greased the shaft so it can still slide, but its movement is now heavily damped by the urethane bush and the rattling is eliminated.
The black Urethane Bush clamped to both the piston shaft and body of the column.
To ensure the hose clips cannot catch on anything as the shaft rotates, I surrounded the joint with a larger piece of PVC pipe inserted inside the rubber boot near the floor. A couple of small self tappers will hold this pipe in place.
A piece of PVC Pipe to prevent the clips from catching.
The bush and PVC pipe need to be split to be fitted around the shaft and column, so in theory, this fix could be done without removing the steering column, just the lower rubber boot would need to be removed. That can best be done by cutting it off with a sharp knife and then gluing it back together afterwards with super-glue. Removing the column is a fiddly job, so I would certainly try this approach first.
The rubber boots, slit up the back to aid reassembly.
If the column has been taken out, now is a good time to check or adjust the steering wheel alignment when wheels are in the straight ahead position, before it is replaced.
Ensure that all the pinch bolts are correctly refitted to the UJs and fully tightened. I put additional lock nuts on top of the Nyloc nuts to ensure they wouldn't work loose.
Note that according to TRW, both UJ's should be refitted with the cross shafts facing the same direction to avoid "cyclic binding" if the UJ's are out of phase:
"Steering column assemblies with more than one universal joint (cardan type) can cause a cyclic binding feel or torque variation at the steering wheel if the u-joints are not in phase with each other".
I assume this to mean that the cross shafts of the UJs should be parallel, like this:
Related Note: I have recently fixed a leak from the input shaft seal on our TRW steering box. See here for details.