Hi all i know its been talked about over and over again but this is one of the next things on my list to do.

what are the weaknesses with the 6 speed and the 5 speed gearboxes?????

I know the standard diff is weak and we can now solve that with the quafe or the gripper diff (others probably but these to are tried and tested)

so what else is the problem with them, are the casings weak, or is it the gears itself or is it a combination of both plus over heating.

any information would be great and may lead to some sort of solution

I'd like to know this aswell!

I remember back in the good old days the big power RS Turbo boys use to use CTS who would shot peen the gears for more strength.

I may be wrong but can't early five speeds have a strengthening cradle fitted to reduce flex?

Any one?

casing will flex due to the increased torque, effectively pulling the main and layshaft apart

Early ones strip gears so no use over 300bhp.
Later type and 6 speeds have no issues with diff upgrade if installed correctly.

is there strengthing plates for the later / 6 speed casings

What's a rough ballpark of the costs involved in fitting an upgraded diff John?

i dont want to just fit a diff because on the later boxes its not fully test yet ie has had a hammering for a few years on track with out fail

ÄÄÄÄhhh...300HP with an Integrale style gearbox, only????!
I used such a gearbox in a Coupe for ~10tkm with 565HP, without failure and a 4x4 (much more stress for gear box and clutch than fwd, only).
Only problem is the 3rd gear at older Integrales... this gear was insufficiently welded and some of them broke at high load. The newer Fiat Coupe Integrale style gear boxes don't suffer from this problem - Integrale user even upgrade their gear boxes with 3rd gear from Fiat Coupe...
Big advantage of the old style gear boxes: you get 3 different strenghtening plates and upgrading gears...
Two friends of mine have Integrales with >>500HP and >>650NM... no problems with these mods...
Nex year my coupe will be back on road with this gear box and 4x4 with >650HP...
Then I can tell you, if it will "survive"...
Juergen

Once again thanks for the info I have read a few different car threads saying about 3rd gear problems so it's not just fiat and lancia with minor issues.

What uprated bearings you using and also is anyone using gearbox oil coolers etc

also where can i get the strengthening plates from for a 6 speed. i can get them made but its faster if i can find the companies that already make them

Right update plates are ordered along with some other special bits and treatment

What are the differences between the late 5 speed case and the 6? Also the difference between the early and the others

On top of this I've been told to try using the Lancia box but I thought the early type was the same?

Once the box is back it will be tested as much as I can with the free time which will include Santa pod and a road trip to the ring, if it survives this il pass on as much info and contacts as I can for people that don't want to be scared of doing a good track day with out calling the RAC at the end off it.

Any info would be great

If you mean an integrale box, then yes, it is the same as the early type, but the gear linkages are different, they also suffer with 3rd gear breaking. The current upgrade they do is to use 3rd gear from the coupe box, as they were made differently.

Yes I was on about the integrate box and I thought I remember rightly they were the same as the early ones just need to find out what the difference is between the other to now.

Somebody mentioned about 3 gear and changing over but I'm trying to build the 6 speed into a much stronger box without spending 10k on a special box

I see the alfas have a straight cut gear kit for the gtv's so this is another option if the 6 speed gear kit after treatment can't take it