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3rd Gear Chatter, rebuild or swap gearbox internals?

I've been busy over the weekend and at the end of last week trying to see if I could get my 3rd gear swapped to my current Pinion shaft at very short notice but this wasn't going to happen, some people could get a 2 day turnaround but after speaking with them they didn't have the really heavy press to actually do the job. The reason I was looking to swap the gear over was that when I had a closer look at the spare pinion end I saw a little pitting and thought it may damage the crown wheel over time but I decided I would fit it anyway just so that I had a 3rd gear for my upcoming road trip.

When I got back to the garage I tried to fit the spare gear set to my current box but when trying to fit the bearing it was sitting proud of the casing and on further investigation the two pinion bearings are actually different in design. My current one has a recess in it and sits further into the diff housing, the spare pinion is just a regular faced bearing so sat proud of the housing.

There is around a 2mm difference in depth for the bearing although I'm sure I've only ever seen one part number for this bearing. Also I'm sure this spare box came from another 996 Targa of a similar year to mine?

Hopefully some picture can explain this better than me.

tOcfQ8q.jpg


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kTOX7hq.jpg


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And the shims from each pinion bearing.

gvdJLNa.jpg


The recessed bearing housing.

F6OlLkS.jpg


How I pulled the bearing in, slowly with half turns on each bolt in turn, pulled in quite nicely in the end, it just took a little time.

BwGO5M2.jpg
 
I have now made the decision to put my original internals back into my original casings as I have run out of time to get the car fixed for this coming weekend. I'll just have to go back to missing out 3rd gear for a couple of thousand miles. :frustrated:

I have refitted the gears and selector shafts but I'm currently having trouble getting the casing to seat fully with the bellhousing part. The selector shafts seemed to have all lined up and both the rear bearings but I'm struggling to get the selector pivot arm wheel on the middle selector shaft, they seem to be getting in the way of each other. I only tried for around 40 minutes today so will have another go at it tomorrow, there must be a sequence or knack of getting it all lined up for it fit? I've not read of anyone having problem with this as long as they have lined up all the selector shafts? :?:

I've had all on getting the middle selector shaft to line up while fitting the casing.

4iuKDe5.jpg


As close as I got today.

7LPDs1P.jpg
 
Goodlick Chris....we know you will get there in the end !
 
FRP said:
Goodlick Chris....we know you will get there in the end !

Eventually yes but back to square one at the moment although it has been a good learning curve.

I watched MC's gearbox video last night and noticed his Pinion bearing also has the recess and his is a 3.4 gearbox but again I only have seen one part number for this bearing? I'm just wondering the origin of my gearbox?

I spent another 3 hours today trying to get the nose seated over the gears, there are 8 elements to line up , 5 selector rods, 2 bearings and one selector roller wheel and all are unseen once you get the majority of the nose over the gears. The main issue is the main gear selector in the centre, it moves about somewhat when dropping the nose over.

I used a couple of screwdrivers to line it up again and also some cable ties in various ways but when I did get it to go over the 5 selector rods the roller wheel that moves the first selector shaft fell off, this happened several times and I had to remove the nose each time, when I managed to get the wheel to stay on I seated the two faces and found the gear selector didn't work, it was stuck solid, so off it came again, this also happened a few times, I lost count of how many times I had to remove it.

This is the offending roller, I held it in place with engine rebuild lube as this is quite sticky but even then it fell off a few times.

2XOekEL.jpg


I did eventually get the casings seated and sealed (used Loctite 5900) but this was a ridiculous amount of time just to put something back that takes 3 seconds to remove, if you don't count the undoing of the bolts. Hopefully it won't take so long next time.

So the gearbox will be back to it old self when its fitted, with a noisy 3rd gear and I will have to revisit all this again when I get more time.
 
Not back at square one - you removed the 3 broken teeth which had a very good chance of munching the whole box and your diff. too.

Dodged quite a bullet there Chris :thumb:

Good luck in getting it sorted.
 
Alex said:
Not back at square one - you removed the 3 broken teeth which had a very good chance of munching the whole box and your diff. too.

Dodged quite a bullet there Chris :thumb:

Good luck in getting it sorted.

At the base of the gearbox there is a huge magnet, all 3 were firmly stuck to that and there was no chance of them coming loose but it should go quicker now its lighter?
 
I'd just be wary of it shearing more off. When my diff. sun gears lost a few teeth, my wheels kept locking up. I'm surprised there's no other symptoms than a chatter in 3rd.
 
Alex said:
I'd just be wary of it shearing more off. When my diff. sun gears lost a few teeth, my wheels kept locking up. I'm surprised there's no other symptoms than a chatter in 3rd.

That's all, at the moment... the the pinion into your diff has larger teeth so would be an issue and I guess the pinion teeth would just pass the missing ones and not mesh correctly when it came across the next available teeth making the car lock up.

I'm just missing 3rd out (going 2nd to 4th) which is a pain but my only option at the moment with the limited time I had/have. I was doing the same in Spain too but should have gotten around to fixing it much sooner than I did.
 

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