Series 3 Transfer Box - Rear Output Shaft Bearings

I've owned an ex military 1984 series III 109 for about a year now, and I have a problem with the transfer box.

With the handbrake drum and rear prop shaft removed I found the rear output flange very lumpy to turn, and I imagine the taper roller bearings supporting the rear output shaft have failed. It's fairly noisy in operation, and has turned fresh oil black and manky in about 6000 on road miles. This opens up a number of questions which despite searching around I haven't found good answers for.

The gearbox itself does have the military type of oil filler - are there any significant differences between civilian and military transfer boxes?

Is it possible to do the job in-situ? I think this boils down to the question of can the front 2WD/4WD part of the transfer box be removed, leaving the rear part containing the transfer gears in place? I think it can be done, but, am I missing something?

In the Repair Operation Manual, it describes two types of output gear, one part helical part straight spur, and another tpye being all helical, and that these different types can be identified by the presence or absence of an adjusting bolt on the end of the selector shaft. Is this identification method foolproof?, or, during the life of the vehicle can these paerts have been mixed?

The shim pack spacing the speedo drive housing off the back of the transfer box looks like there's lots of ways for oil to leak out! What's the best way to seal them up?

Are there any other jobs I should be doing while I've got the transfer box "open"?

Thanks for reading this far! Any hints and tips and sharing of experience would be most welcome!

there are 2 types of t/box standard including civillian and military and 1 ton which has the helical gears, front output shouldnt come off with bell housing in place ,you dont seal the shims each is like a gasket in itself

Doesn't the 1 ton have a different (convex as apposed to concave) input gear cover plate?

jamesmartin said:

front output shouldnt come off with bell housing in place

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Thanks James - I appreciate your taking the time to read and reply.

I'll be shopping for a mainshaft nut tool then....

Tall Ratbag said:

Thanks James - I appreciate your taking the time to read and reply.

I'll be shopping for a mainshaft nut tool then....

Click to expand...

the front taper bearing is secured by a circlip on the the shaft quite a few of the replacement bearings have a large chamfer which the circlip will sit in removing the free play the gears need its something to look out for

jamesmartin said:

the front taper bearing is secured by a circlip on the the shaft quite a few of the replacement bearings have a large chamfer which the circlip will sit in removing the free play the gears need its something to look out for

Click to expand...

That's quite a nasty problem to find - thanks for alerting me! Are there any particular brands of bearing to avoid?

its tricky as bearmach, britpart and all makes have sent good and poor examples over time

above the chamfer isnt too bad some are much greater and so poor

The bearings arrived today - the front one's a Koyo, and the speedo end is a NTN. So, not Timken or SKF, but, not sweatshop specials either.

It's going to be a few weeks before I get the chance to do this job. I'll report back on how the Koyo bearing fits - the inner corner detail is a bit unusual, there's the flat abuttment surface, a small step (~0.5 mm), and then a convex radius (~1 mm). How this will butt up against the circlip isn't obvious... yet.

In other news, passed the MOT today, so that's going to be another year of hindering right thinking people on Britains A roads!

In the hope that it may be useful to someone else attempting the job, here are a few notes and comments about the job so far, ...

If you haven't got them, you'll need some Whitworth spanners! (but there are also some A/F, for good measure)

To save stuggling when the unit was removed, I put the handbrake on hard, and then removed the nuts holding the front and rear drive flanges.

I hadn't realised that the transfer box clears the pinion on the end of the gearbox mainshaft - although it's obvious if I had only read the green book properly! Happily, my pinion is OK, and so, it's staying put!

As mine is a military Land Rover, the cross member under the transfer box can be removed - this means that the floor doesn't need to be taken out. The green book suggests removing the handbrake relay and possibly also the exhaust; I didn't need to. I did remove the O/S mounting bracket to give some clearance for the handbrake relay.

After removing the intermediate gear, I removed the internal fasteners which hold the transfer box on to the back end of the gearbox. Two of the three studs came out, causing gearbox oil to leak out through the hole. To avoid this, I should have drained the gearbox oil earlier, while I was draining the transfer box.

Once out, the front transfer box seperates easily. I used the front output shaft itself as a pressing spacer to push the old bearing out of the front of the front transfer box. I also found that the 4WD drive dog made a perfect special tool / spacer for pressing in the new ball bearing back in.

Although the Hi/Lo and 4WD selector rods were moving freely, I noticed that there was some water in the front end caps. Now, during my ownership, I haven't been in any deep water, and I'm a bit puzzled how the water got in there. Is there a seal which fails?, or, is it just condensation, and the end caps are the coolest part of the system? Is there anythig I can do while it's apart to prevent or reduce the problem?

Sorry about the essay!, thanks for reading!, Part 2 to follow when I've dealt with the taper roller bearings on the rear output shaft.

Here's Part 2, as threatened!

Removing and replacing the bearings went largely as per the green book. I found it easier to release the high gear circlip, and remove the shaft, low gear and high gear before removing the front outer race. This then allowed me to drift out the front outer race with lots of room.

The bearings, in particular the larger rear bearing, were completely ruined. The high gear circlip actually looked more like a snap ring - it was only when I looked at it more closely that I found the ears at the tips of the circlip had broken off. I imagine that the circlip debris was what had damaged the bearings. Both old bearings were Timken, and the I would say that the corner detail was compatible with the circlip. I don't know if the shaft had been badly assembled last time it was overhauled. The end float for the high gear was within tolerance. Has anyone seen this type of failure before?

In setting the bearing preload, I found the intermediate shaft, at 1.48 kg was well suited as a test mass.

I found some pitting on the flanks of the helical teeth on the intermediate gear. Finances don't allow a new one, so, for now, it's gone back in. If anyone has a good used one that they would like to exchange for beer tokens, please get in touch.

The end result of the job is that the ride is much quieter - the only problem being that I can now hear noises that will need fixing that I had been missing before!

Thanks for reading, and thanks in particular to James for his helpful advice. Cheers!