Series 3 S3 Gearbox rebuild - How do I know what's buggered?

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Kiwi Landie

Kiwi Landie

Active Member
Posts
116
Location
New Zealand
OK - Finally got both the boxes stripped and everything labelled in little zip lock bags.
So far so good.
Now the various manuals all say things like 'inspect and replace worn parts'. This is all very obvious when something is broken or in my case missing completely (synchro flat spring - fell out the drain plug with the oil but had clearly gone around a few teeth on its way out). What I need a bit of guidance with is how do I decide which if any of the gears are knackered? They all look pretty good to me. There are no chipped teeth, and there is just the slightest hint of 'polish' on the sides/ends of some of the teeth on some (not all by any means) of the gears. Likewise all the splines on the shafts and the various dog teeth look reasonably OK (ie: not just rounded blobs). The transfer case internals also look pretty good but the Haynes manual has a picture of a 'badly worn intermediate shaft' but the photo is black and white and tiny, and to my eyes the shaft looks just like the one in my gearbox! Short of finding a gearbox expert (I live in rural New Zealand), are there rules of thumb to help determine what's knackered and what's not?
Before someone asks, I wasn't able to hear this 'box running before stripdown. My S3 came with an S2a gearbox which I've sold off to help finance the rebuild.
S3 1978 Suffix B box and transfer case.
Cheers for any wisdom offered - and sorry for posting this originally in the wrong location. I'm new here.....
 
Did you check the oil with a magnet when you drained it . Gives a clue to amount of wear / metal content. Shiny gear teeth is the case hardening wearing away. still hard to judge with out having driven it.New brass bush and bearings if needed rebuild refit and see how it goes.
 
Do some google images searches for things like "gear spalling" and "worn gear dogs" and you will see pitures of good and bad. Ther will be some measurments so you need to get the manual and check those. The hardest to see will be where gear dogs (engagment teeth) have worn out of shspe, this is what makes a gear jump out of engagment". The torque must hold the gear in, that needs parallel teeth of the laterr "coffin shaped" ones. If the teeth are work then the torque pushes the gears apart. I thik the bearing ca be a dillemma, they are not expensive to replace, but they are hard to do and it is poosible to damage the casing, look carefully at the condition of the cages, they can break up. I found it really useful to put the gear cluster together on the bench vertically (on a Workmate with the shaft through it) then move all the gears by hand and see how they meshed and how far they engaged.
 
Here are (hopefully) a few pics of most of the moving parts. By my reckoning, I need a new 3/4 synchro clutch, the little teeth look pretty sad on that. New baulk rings wouldn't go amiss and also the gears for 1 and 2. It's the little teeth that look the most knackered, but they don't look that bad to my inexperienced eye.
Any advice appreciated.
IMG_9940.JPG
IMG_9935.JPG
IMG_9933.JPG
IMG_9945.JPG
IMG_9937.JPG
 
That all looks quite good, obviously its worn but not really badly. The usual problem is jumping out of 3rd so look at the teeth that engage 3rd. The new 3/4 syncho will have one set on and the other will be on the 3rd gear. I seem to recall there may be 2 types of 3/4 syncho, one with striaght dogs and one with "coffin shaped" - help me someone - are the different numbers or do they just supply the later type for everything?
 
coffin shaped dog teeth are only fitted on the later suffix d boxes which this box isnt, dog teeth on 1st and second need a good look as do teeth on layshaft (straight teeth for reverse)and rev idler, cant see enough of the 3rd 4th synchro dog teeth to tell
 
Thanks for that advice guys. I've had another look at the various components and decided that the transfer case end is all good enough to be reused as-is. There was a bit of light surface rust on the intermediate gear but nothing that didn't clean up with emery cloth and no pitting on the teeth. The mainshaft end gear was pretty corroded because this box has been sitting in a gravel pit with its end bearing housing missing for a few years and the rain getting in, but I'm fitting an overdrive, so this gear is surplus anyway.

The layshaft is (again to my inexperienced eye) near enough unmarked. There is some minor 'shine' on the reverse gear teeth, but the helicals are all very good (see below)
IMG_9946.JPG

The 3/4 synchro clutch is definitely more worn at one end than the other (below). There's also a bit of corrosion kicking around here as well.
IMG_9948.JPG
So it seems to me that I can reuse most of what I took to pieces, which is great. I checked the endfloat on the mainshaft 1/2 gears around the bronze distance piece and it is excessive at 15 thou, so there'll have to be some fettling there, but overall - not a bad result.
The very end of the main shaft (where it will go into the overdrive) was a bit corroded when I picked the box up:
IMG_9952.JPG
I cleaned it up a little with some emery but it is still a little pitted. Is this type/extent of damage terminal in anyone's experience?

Thanks for the help so far and any other pearls of wisdom.

Cheers
Andrew
 
There does look to be som espallig on teh flanks of the hleical gears, its not clrear in the photo. A little bit of pitting can be OK but if its starting to flake off the tooth face it deteririates fast. The pitted shaft, is that the end that goes into the plain bearing in the OD? These breaings are a plastic / metal unit. There must be no sharp edges and it needs to be a good fit to support the shaft but when you are in top there is no rotation, it only moves when the OD is in then its a 20% (roughly) differnce. I think you may get away with that if you polish it with a strip of fine emery.
 
Kiwi Landie said:
Thanks for that advice guys. I've had another look at the various components and decided that the transfer case end is all good enough to be reused as-is. There was a bit of light surface rust on the intermediate gear but nothing that didn't clean up with emery cloth and no pitting on the teeth. The mainshaft end gear was pretty corroded because this box has been sitting in a gravel pit with its end bearing housing missing for a few years and the rain getting in, but I'm fitting an overdrive, so this gear is surplus anyway.

The layshaft is (again to my inexperienced eye) near enough unmarked. There is some minor 'shine' on the reverse gear teeth, but the helicals are all very good (see below)
View attachment 171767
The 3/4 synchro clutch is definitely more worn at one end than the other (below). There's also a bit of corrosion kicking around here as well.
View attachment 171768 So it seems to me that I can reuse most of what I took to pieces, which is great. I checked the endfloat on the mainshaft 1/2 gears around the bronze distance piece and it is excessive at 15 thou, so there'll have to be some fettling there, but overall - not a bad result.
The very end of the main shaft (where it will go into the overdrive) was a bit corroded when I picked the box up:View attachment 171769 I cleaned it up a little with some emery but it is still a little pitted. Is this type/extent of damage terminal in anyone's experience?

Thanks for the help so far and any other pearls of wisdom.

Cheers
Andrew
Click to expand...
dont clean up with emery use a wire wheel
nothing looks amiss there the end of mainshaft wont be and issue, pic of dog teeth needs to be edge on as below
upload_2019-3-7_10-13-5.jpeg
 
Thanks guys.

I temporarily fitted the end of the mainshaft into the overdrive bearing yesterday. It felt snug with no play, so I guess that's a bonus. I'll give it a further clean up with a wire wheel as James suggested and see how I feel. A new mainshaft isn't the end of the world, even down here at the end of the world....

Back with another couple of photos later on.
Cheers
Andrew
 
Kiwi Landie said:
Thanks guys.

I temporarily fitted the end of the mainshaft into the overdrive bearing yesterday. It felt snug with no play, so I guess that's a bonus. I'll give it a further clean up with a wire wheel as James suggested and see how I feel. A new mainshaft isn't the end of the world, even down here at the end of the world....

Back with another couple of photos later on.
Cheers
Andrew
Click to expand...
it doesnt really do much the shafts supported by a bearing and splines in the over drive
 
Here's a couple of photos of the 3/4 synchro clutch from the side, as suggested. The inner teeth are all different widths! So this unit has got to go.
I tracked down an outfit called T.A.S in Italy who apparently manufactures these for various suppliers, including Britpart. T.A.S seem to have a good reputation, but Britpart rather less so. Has anyone got any experience with a Britpart-supplied 3/4 synchro? Are they all rubbish or is it possible to find a supplier who is selling the T.A.S manufactured units? I tried to buy direct from T.A.S, but they told me their entire stock was pre-purchased by various UK retailers and they could not send me a single unit.

IMG_9966.JPG
IMG_9968.JPG


Cheers
Andrew
 
I use shop4autoparts, they are UK based and get some of the parts manufactured locally (Coventry). I spoke to them at length (very helpful) when I was ordering the parts for my own box and OD. The internals of my OD came from them.
https://www.shop4autoparts.net/Vehi...kruUTBYIUzy3s/Xo4o9lM03HlFtHUzwKERN9lcy5JKA==
I also spoke with a number of gerarbox overhaul engineers and learned a lot:
1 When they get customers bring in gears in OEM boxes they are invariabley Britpart that has been reboxed. One guy said that other than the chap in Cyprus (who you will see on e-bay and who bought all the MOD Cyprus stock) every gear in an OEM box a customer brought in was not OEM.
2 The Britpart and other gears last OK, there is no particural problem with them and so its not worth paying more. I have a number BP gears in my box and they work fine.
3 A number of the Italian gear suppliers use a laser copy machine. They take a part and make an exact replica, its much cheaper and faster than getting the drawings (and gets around EU copyright ), but (and its a big but) the process copies any imperfections in the original too. Its fine if they have a new master gear, but in some cases they have used 2nd hand masters and made batches with built in wear.
 
Kiwi Landie said:
Here's a couple of photos of the 3/4 synchro clutch from the side, as suggested. The inner teeth are all different widths! So this unit has got to go.
I tracked down an outfit called T.A.S in Italy who apparently manufactures these for various suppliers, including Britpart. T.A.S seem to have a good reputation, but Britpart rather less so. Has anyone got any experience with a Britpart-supplied 3/4 synchro? Are they all rubbish or is it possible to find a supplier who is selling the T.A.S manufactured units? I tried to buy direct from T.A.S, but they told me their entire stock was pre-purchased by various UK retailers and they could not send me a single unit.

View attachment 172227 View attachment 172228

Cheers
Andrew
Click to expand...
theres is teeth of 2 different widths by design its the step in bottom pic on the bottom right that shows it needs replacing
 
Hey thanks guys. I have now located a chap close to me here in NZ who has rebuilt a bunch of these boxes and he's agreed to look through my collection of parts and tell me what else is knackered. I've checked out the Shop4Autoparts site and they look like they know what they are doing, so thanks very much for the lead there. I'll get an order together and see how I get on. Can't be that hard.......
 
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