ALFAGTV6.COM

[gtv-racer]

Hello,

I'm totaly rebuilding an alfa 75 3.0v6 milano. When i'm done with the chassy i'm going to supercharge/turbocharge it. I already built in a megasquirt.
One problem. i'm planning on exeding the 300hp transaxle limmit. I've read somewhere that there is a clamping constuction of the transaxle. than it can take a small 400 hp with stock rev. has anyone got pictures of it or more info. i thout it was done by the south african guys. A gearbox up front is not an option for me. to much work.

I aready supercharged my alfa gtv 2.0ts (916).
Now i'm going for the real thing

Here a movie of the gtv with eaton m45 supercharger. It's a safe setup for my daily driver. It puts out 196 crank Hp and has a very flat torque curve. It has an air to air intercoler and the engine is completely stock exept the bigger injectors:

http://www.youtube.com/watch?v=y3m59wNp ... re=related
http://www.youtube.com/watch?v=wgX9iOfKvnw&NR=1

[Greg Gordon]

Hi gtv-racer:

Nice work supercharging your 916 TS.

I have not done much work in the area of strengthening the transaxle, a few others here have so hopefully they will chime in. My dad and I have looked into this issue very carefully and arrived at the following conclusions.

The overall problem seems to be that so many things in the transaxle fail around the same point (evidently about 350rwhp according to Barry H.) that it's essentially impossible to solve all the issues, and more effective to go to a front mounted transmission, which in itself is a huge job.

There are three major weak points in the transaxle I know of. First, the pinion gears are weak. I have seen two of them fail on stock engines (both 1983s so it may be a bad production run). In any case plenty of other people have destroyed pinion gears with modified engines so that's a known weak point.

I suppose some treatments could help the pinion gear a little, perhaps, shot peening, cryo treatment etc.

Next, the gears try to force themselves apart in a fore-aft direction due to the forces and angles at which the gears are cut (like almost all transmissions). In the Alfa transaxle it seems they are actually able to do this enough to separate, and when they crash back together, BANG, it's over. Something in there flexes enough to allow this to happen, I think it's the area around the intermediate flange, which could be strengthend. It's possible to make reinforcement plates for this area, but I don't know if they will do any good.

Third, the gears try to force themselves apart in a up-down direction. I have heard of people making girdles, or using straps around the gear box to try and minimize this. None have been successful as far as I know. It's interesting to note that even if you go with all aftermarket straight cut gears to eliminate the fore-aft movement issue, you can't eliminate this up-down issue.

Even if you do go with straight cut gears and somehow eliminate the up-down issue, you are still stuck with the pinion gear that fails about the same point as everything else.

What does all this mean? You could sink a ton of money into the transaxle with straight cut gears, cryo treatment, special reinforcements, and on add enough strength to support another 25 horsepower.

Greg Gordon,
www.hiperformancestore.com

[Giuliettaevo2]

Welcome..

Another one from Holland. I have been following your work on the SCARB forum, very nice work with all the welding and stuff.

Just put a box up front, you know you want too...

Or contact Dominic from the Scarb forum and ask him about the Porsche gearbox he has.

Greetings Remco

[gtv-racer]

Hi greg,

Thanks for the answer. Too many problems for the transaxle...
It's a pitty but now it is very clear to me.. i tought there was only one problem till 350hp..

Box upfront is a nice sulution but to much work for the first fase.
Also orderd your book today. Looking forward to it.

Hello you from Cuijk The Netherlans. Is was inspecting you
Maybe the porche transmision is a nice one but i hope it is in my reach (money). i will reseach this one. Has it a complete transaxle unit (clutch, diff and gear in one)

I'm almost finishd welding on my beast. Looking forward to have it boosted . still in discusion with myself or i gonna torbocharge or supercharge it. I like the V6 sound a lot. Supercharging it may loose the 6 from grunting it so nice but you guys can tell me that. The supercharge wine is a nice sound tough. The scream gives me the goosbumps.

greetings

[Giuliettaevo2]

Porsche uses a torque-tube fom the engine to the gearbox. Clutch is on the flywheel at the engine side.

most difficult would be to make the torque tube fit the v6 and under the transmissiontunnel.

[gtv-racer]

Here a link to my rebuilt:

http://forum.alfaclub.nl/viewtopic.php?t=40185

[doretyjohn]

Hello
My name is John Dorety
I am trying to sale a well prepared GTV 6 E Production race car. I set up a thread under cars for sale. Thanks for the thread here.

[gtv-racer]

I read that the Nissan Xtera m62 superchargers a 4th generations one. Are they the same then as an mp62 and then i mean flowcharts and volumetric effincientie. I noticed that it didn't have the s port like the mp62...

[kterkkila]

I have not done much work in the area of strengthening the transaxle, a few others here have so hopefully they will chime in. My dad and I have looked into this issue very carefully and arrived at the following conclusions.

The overall problem seems to be that so many things in the transaxle fail around the same point (evidently about 350rwhp according to Barry H.) that it's essentially impossible to solve all the issues, and more effective to go to a front mounted transmission, which in itself is a huge job.

There are three major weak points in the transaxle I know of. First, the pinion gears are weak. I have seen two of them fail on stock engines (both 1983s so it may be a bad production run). In any case plenty of other people have destroyed pinion gears with modified engines so that's a known weak point.

I suppose some treatments could help the pinion gear a little, perhaps, shot peening, cryo treatment etc.

Next, the gears try to force themselves apart in a fore-aft direction due to the forces and angles at which the gears are cut (like almost all transmissions). In the Alfa transaxle it seems they are actually able to do this enough to separate, and when they crash back together, BANG, it's over. Something in there flexes enough to allow this to happen, I think it's the area around the intermediate flange, which could be strengthend. It's possible to make reinforcement plates for this area, but I don't know if they will do any good.

Third, the gears try to force themselves apart in a up-down direction. I have heard of people making girdles, or using straps around the gear box to try and minimize this. None have been successful as far as I know. It's interesting to note that even if you go with all aftermarket straight cut gears to eliminate the fore-aft movement issue, you can't eliminate this up-down issue.

Even if you do go with straight cut gears and somehow eliminate the up-down issue, you are still stuck with the pinion gear that fails about the same point as everything else.

Now we have three known problems. First might be related to housing or shaft flex as well. Wrong tooth contact during flexing? Or then the pinion is just too small. How it's compared to pinions of other cars that can handle higher torques?

Second and third, what the failures look like? Does some of the gears drop their tooth, or something else? It would be interesting to figure out whether it happens due to housing flex, shaft flex or just wrong dimension again. Also interesting is that what gears usually go first?

The 1st, 4th. and 5the. are located near to bearings. The 2nd. and 3rd. more far, thus shafts might flex if those go first. The 1st. and 2nd. also cause high radial forces, but 4th and 5th. shouldn't be a problem anymore.

[kevin]

Here is that latest victim. If the pinion was the same size of the Alfa Sei then we could atleast eliminate this problem. I did have a broken pionion sent to a metal lab which as mention before they found oxidation in the root of the pinion teeth which occcured during incorrect heat treatment, as it allowed an ingress of oxygen.
The strenght was way off our scales past tool steel. Way past EN 40.
The drag racing guys here actually soften the pinions in the 1000hp cars but they only do a few runs so wear is not an issue.

[MR2 Zig]

Kevin,
Maybe annealing the pinion and then redoing the heat treatment would work. You then would have the option of setting the harness lower than stock but not soft either.....Another of my wacky ideas

[Mats]

Interesting, maybe shop-peening the pinion might be a good idea then, in the root of the teeth that is. Doesn't fix the heat-treatment issue but might just keep it alive.
Wonder if this is just in some boxes? Never even heard about a stripped pinion over here.

[slyalfa]

hmm as that box has straight gears. It should not of had the box spreading apart problem.
but I guess the pinion its self is still be trying to move in or out as it is not straight cut. and if it moved much at all ether in or out I could see it bust apart.

I still think a vett box is the answer with or with out the torq tube.

[Mats]

The "spreading apart" problem comes from the fact that the gears are pushing on each other radially due to the fact that the contact faces are at an angle out from the axle, not along the lenght.
So you will still have issues with bending in a straight cut box.

[gtv-racer]

interesting. Does anyonne got pictures of other failures?
And what usualy goes wrong with the pinion then?
And are whe talking about 350 RWhp or 350 hp at the crank?

This beacuase 350 RWhp is fine for me!