Alfa V6 FWD Gearbox Strength

[turbonutter]

I am looking to turbocharge a V6 engine again, this will be a transverse installation, with around 450bhp.
I have done a similar project about 15 years ago and used the standard 164 gearbox.
There have been many changes since then, and a lot of new gearboxes.

Does anyone know which of the front wheel drive boxes is the strongest?

Is the 6 speed box stronger or weaker than the 5 speed.
Is the Selespeed box better or worse than the manual box, or should i just stay clear of the selespeed?
Any particular model that had a more robust gearbox.

Thinking logically the GTA should have the strongest box as it is the highest output?

Any sensible modifications that can be done to improve the gearboxes.

A lot of questions, I hope someone can help

Thanks
Neil

[giulia_veloce]

Hey Turbonutter.

Sounds great what you are dooing = turbo.
I have had 2 failures with the 6 speed gearboxes out of a current GTA + Gt.
The diffs came out the side of the box.
Required new diff assemblies and cases.
These are standard cars.
I didnt do it,customers did.
An engineer checked them and said the internal 4 gears and pin were too small causing the failures.Also had a failure on a 156 twin spark 4 cyl.
All the customers said they were driving normal when the cars stopped.
Gearbox oil everywhere.
And just last week,the dealer across the road ,picked up a GT.His father drove it 5kms,and it chucked a diff.
Anyone have any other experiences with diff failures on current Alfas ?
I love my Alfa,but if I was going to drive one extremely hard,like I always do,it would be my 2 litre 105s.
I dont have confidence in driving current Alfas hard because of the failures in the diffs.
These are probably isolated cases,and not many would have the problem.
Just thinking twice about you Turbo charging and diff failures.
Other comments welcome.

Robert

[Yaninnya]

Hi Neil,
Loads of questions... First things first: Torque is killing the gearbox not power so more important is what torque you want to develop.
Stay clear from Selespeed. It is the same (more or less) gearbox with auto electrohydraulc gear change: slow and just annoing.
5 and 6 gear boxes are basicly from the same family - C.503, so no difference in strengh. IIRC FIAT offically quoted 310 Nm as maximum torque, but GTV BiTurbo made by Novitec managed 432 Nm without strengthening plate.
Strengthening plate is a laser cut SS plate which is put in between the two lower parts of the gearbox housing, it stops the two shafts from spreading apart under load and breaking the gearbox casing which they do on higher powered cars. You can buy it from Gralecoupe from Fiat Coupe UK forum. No connection, he just seling the plates for 50% of the Walkers or Auto Integrale.
With so much torque you need a LSD. you can use Q2 but much better is traditional plate type diff. You can get it from AHM or Autodelta but it is quite costly. But plate diff will not explode like standard ones.
When you will be building the gearbox don't forget that there are dosens of different types of speedo drive, gearshift mechanism, etc. And you need to think about flywheel and clutch as well.
I hope that helps a bit.
Jan

[turbonutter]

Thanks for the replies.

The engine will be for a Lancia Stratos replica, the same as my last project, hence not a car specific post.

I had heard/ seen a lot of reports on diff failiure. My previous turbo engine had a 5 speed box from a 164. This had an LSD supplied by Gatwick Alfa. No problem with the dif, but the Input shaft bearing failed wrecking the box. With the second box I had the bearing changed for the later roller type and had no more problems with the Gearbox. (the car was destroyed by fire, but that is another story)

I realise that it is the torque that destroys gearboxes, if the engine follows a similar path to the previous one then it will be in the region of 550Nm. I realise this is a lot for the gearbox to handle, hence the post!
So a strengthening plate looks like a must. I will be using an LSD, probably the AHM one.

Re the different Spedo drives/gearshifts etc, that is not a big problem, as it is a special anyway, due to the engine being used mid mounted.

Flywheel & clutch I am already investigating.

The project is just beginning so at the moment just trying to gather as much information as possible.

Thanks

Neil

[Yaninnya]

Hi Neil,
First of all, I'm not any sort of Alfa g'box specialist, just done some investigation as I need a strong g'box for my project.

Quote:

Originally Posted by turbonutter The engine will be for a Lancia Stratos replica, the same as my last project, hence not a car specific post.

[CorseChris]

Not so extreme as Neil...but me too. I've tried to PM Gralecoupe re the plate...I'll let you know what he says. Thanks for raising this one too Neil.

I was leaning towards a 166 6 speed box with a Q2 for mine but the plate sounds like an excellent bit of insurance on any of the family of boxes.

If my blower ever arrives, I'm hoping for somewhere between 10 & 14psi on mine so maybe 350/350 or a wee bit more for me.

[Yaninnya]

I think that I shoud mention that everyone who want to see yours Stratos (and you ;-))) ) must get a copy of Auto Italia June issue (no 158).
Jan

[CorseChris]

Quote:

Originally Posted by Yaninnya I think that I shoud mention that everyone who want to see yours Stratos (and you ;-))) ) must get a copy of Auto Italia June issue (no 158). Jan

[turbonutter]

Quote:

Originally Posted by CorseChris Not so extreme as Neil...but me too. I've tried to PM Gralecoupe re the plate...I'll let you know what he says. Thanks for raising this one too Neil. I was leaning towards a 166 6 speed box with a Q2 for mine but the plate sounds like an excellent bit of insurance on any of the family of boxes. If my blower ever arrives, I'm hoping for somewhere between 10 & 14psi on mine so maybe 350/350 or a wee bit more for me.

[Yaninnya]

Quote:

Originally Posted by CorseChris The car was also featured in PPC magazine recently, but at least I avoided a mug shot in that one. No such luck in AutoItalia - they insisted on one. Not a pretty sight.... The steering problem they referred to has been resolved - basic setup error. I know better, but had been BSed by a so-called expert and was running it with toe-out at the front. Quick tweak and it's sorted. It would be nice to take it back to the circuit at Longcross where the photos where taken and have another run some time. ...and it's called a Corse (with an E, not a Corsa as in Vauxhall), but we'll forgive them that as they did a good article I thought.

[cookie]

are you sure they said toe out on the front and not the back! id love to have one myself but unfortunately no one makes a half decent kit let alone a decent one. id stick with the 5speed 164 box and fit the rudamentary out board capilery lsd from the fiat coupe.

[Yaninnya]

Quote:

Originally Posted by cookie id stick with the 5speed 164 box and fit the rudamentary out board capilery lsd from the fiat coupe.

[CorseChris]

Quote:

Originally Posted by turbonutter Chris, I have seen a lot of forum posts on gearboxes and the Q2 diffs, seems that there is a problem with the diff failing, especially on high power engines. The diff comes through the side of the box!! Plate diffs are stronger....

[turbonutter]

So far only found two sources AHM for £695 +VAT & Autodelta for 995+vat, so thats an easy choice.... Will keep looking though, as i didnt use either of those for my last car.

[CorseChris]

Mmm....think I'll try a stock box first and see how it lasts!

Anyone know where the plate fits? Can't be that hard to make a template and get one laser-cut.