SIII Gearbox Overhaul

[Tony_C]

evening all (i suppose morning to some also)

I am currently staring at a pile of bits that was originally a SIII gearbox, number 90104501 A.

Before i took this out and apart i had a problem - jumping out of third when i lifted off the throttle - was fine under power.

Now i have it apart i see i have a few teeth missing off the splines that stop the constant gear slinging backwards along the layshaft - i don't tbeleive this to be a big deal.

I have just looked at the clearances (end float) on the 2nd/3rd gear on the mainshaft - there are none - so it looks like a replacement 2nd/3rd gear distance sleave.

now my question, would a worn distance sleave (and now the lack of clearance) result in the "jumping out of third problem"?

I intend to replace the detent springs on the 3rd 4th syncro, is there anything else i should look at or replace while i'm in here?

Many thanks in advance

Tony_C

Notts, UK

[bill van snorkle]

Check the condition of the male splined teeth on the 3rd/4th synchro assembly for tapered wear, and also check the mating female splined teeth on 3rd gear itself for tapered wear. If the gearbox has been disassembled at some previous time ( very likely) it is possible that the synchro assembly has been refitted back to front, and if so this is likely the cause of your problem.Some of the male teeth on 3rd/4th synchro assemblies are made thinner and offset so that all teeth take drive loads, but less teeth are in contact on overun (coast). It was intended that the higher tooth pressure of having less teeth in contact would prevent jumping out of gear on over run. There is a machined relief at one end of the internal splines inside the synchro assembly. this end should face 3rd gear upon reassembly. While you are at it check the male dog teeth on both 1st and 2nd gears. There are about 4 teeth that are thicker than the rest that are also prone to taper wear that will also cause jumping out of gear under engine braking.Any components with taper worn dog teeth should be replaced.

Bill.

[Tony_C]

Thanks Bill - unfortunately al the teeth look fine and the syncro is the correct way round.

bit stumped now - just getting some prices on a sleeve, 3rd gear and new syncro from paddocks - probably just as well to change them as i'm in here.

cheers

Tony

[Dano]

If the gearbox has been disassembled at some previous time ( very likely) it is possible that the synchro assembly has been refitted back to front,

when I did mine i diddnt realise it could go back wrong!! hope it is in the right way, I guess I'll soon know if I ever get the engine running

ps Bill how you ever do those Synchro springs in situ I will never know, perhaps you are in the wrong game and should take up Keyhole surgery

Tony, sorry for highjacking the thread

[bill van snorkle]

[quote name='Dano' date='Apr 14 2008, 08:56 PM' post='254892'

ps Bill how you ever do those Synchro springs in situ I will never know, perhaps you are in the wrong game and should take up Keyhole surgery

Tony, sorry for highjacking the thread

Around 20 years ago I began what was to become a 10 year stint working for'' Bodge It an Scarpa Used LandRovers'' I have changed the name to protect the guilty, but you get the idea. We'd get about 2 vehicles a week requiring synchro springs replacing in the quickest time possible to maximise profits. It used to frustrate me having to go to all the work removing the floor and seat box, plus all the nuts and bolts and mess involved in removing and opening the transmission and refitting it just to replace 3 dollars worth of bits. So one day I bent up some stiff stainless steel wire hooks, and together with a telescopic button magnet I found I could do the whole job start to finish in a comfortable 90 minutes or so. Basically,with the t/case in neutral,rotate the mainshaft so that one of the synchro spring flats on the synchro hub assy is at top dead centre. Slide the synchro into 4th gear. feed one spring into the back of the synchro assy from the 3rd gear end whilst pulling upwards on the bronze outer with a U shaped wire hook. Once the front of the spring clip has been pushed to half distance I would pull upwards on the front of the clip with a 90 degree wire hook whilst with a large screwdriver sliding the synchro into 3rd gear. In most cases the clip would click into position. Then slide synchro assy back to neutral, rotate mainshaft 120 degrees and repeat the procedure until all 3 spring clips have been done. Sounds easy, but unless one works on LandRovers for a living it would be difficult to get enough practice to become proficient at it.

Bill.