ALFAGTV6.COM

[gtv-racer]

Today i got a new sound from my gearbox.... a grinding sound.what could cause this. Only below 2500rpm for now . also when it was in fifth gear it poped out .
Think i'm pushing it to hard with 0.6 bar with a 0.7 peak with the high lift cams. At the red line thats 16000 supercharger rpm. Would that be close to the 350 rwhp limmit. The charger consumes 35hp at red line. I know torqeu is the killer but don't now the numbers...

[kevin]

Drain oil and see what type of metal fillings come out . You will recognise where there from .. Is it all gears because if it is you have chipped the pinion and its only a matter of time before all the teeth go . This can lead to a break in clutch housing so its worth it not to push it yet . The sudden break transfers shock into housing . Also you can jack car up and spin wheel with your hand in neutral . You should hear it clearly if its in diff .

[gtv-racer]

Nice one, oil drian. Gives me some idea wit less work! It's in all the gears..

[Giuliettaevo2]

Most likely the diff...

[kevin]

As its on same subject of supercharging a 75 , I snapped some pics of his very neat rotrex installation on this car at our annual AROC gathering last month .

[kevin]

Some of the car which was properly sorted with some big torsion bars and brake upgrade . There just seams so much space in the engine bay .

[75evo]

Wow nice! A blow through setup. I would like to put this on my 3.2! Do you have the owner's contact?

[Greg Gordon]

It's rare to see an L-Jet setup with a supercharger, but it can work! Looks like this car has no AC, and probably not much more than 5psi. Not how I would have done it, but very cool, I like it.

Greg

[gtv-racer]

Always nice to see those builts. Thanks for charing.

Still haven't found any time to have a look at he transaxle's oil. But if it's the diff, i have strong ideas to put in an
928 gts Porsche manual box. Already bought one for 100 euro. Couldn't let that one go. if so , toque tube will go in also. I think it not to hard. But i will take measurements when i Jack it up for the oil check. Place of the clutch Maybe ill put it at the back and mill a comlete bellhouse

[kevin]

I had a 928 box but it did not fit in the Dedion . I still have the pics . Out of interest which box have you got in . Is it the big pinion from the 75 3.0 . Once you strip it and see the failure post the pics .

[75evo]

Cool, then we will get the definitive answer on hot to fix the engine misalignment. Actually Kev you've already fixed that issue in on of your builds.

[kevin]

Note this is under racing conditions with a 3.7 24v . The engine misalignment and bracing of the engine fixed my prop issues combined with coupling cage . The extra bracing on the clutch housing fixed the clutch issues with the standard clutch flywheel . The correct gearbox oil, diff cooler , outboards brakes , side exhausts AND smoother driving solved the gearbox issues on the SMALLER 10/41and10/43 pinions .
HOWEVER the the guys who went a step further used the crown / pinion from the 75 3.0 as its much bigger than the previous two pinions mentioned combined with stiffener plates around the bearings on main shaft in gearbox could thrash that box all day long EXCEPT on the big twin turbo motors as these stripped the gears . But now we talking 450hp on wheels and not even straight cut gears .
So I would wait and see what broke first . Oh also I used the BMW centre coupling which is exact pcd and 10x stronger than the Alfa one but its 5mm wider .

[gtv-racer]

I had a 928 box but it did not fit in the Dedion . I still have the pics . Out of interest which box have you got in . Is it the big pinion from the 75 3.0 . Once you strip it and see the failure post the pics .

Yes i have the 3.0 gearbox. I also did think of the diesel box with the big end reduction but they say it has smaller pinion with a smaller crownwheel wich push up he ratio.

Can you please post he pic's of The 928 gearbox and the dedion? There is a long and short version of the posche transaxle. Don't know wich i have...

[Giuliettaevo2]

Some 924 and i think all 928 have the version where the stubaxles are in the most rearward part of the gearbox. The 944 has the stubaxles more forward in the box and that gives you problems as the gearbox will then hit the dediontube.

[kevin]

This is the one I measured up a few years ago . It just seemed to much work at the time . Little did I know I was gonna cut the car up and put box in front . And I did not want to touch the Dedion .
I think it will still be cheaper reinforce clutch housing , strengthen up box on main shaft to stop any play or whip as it just takes fractions to break the pinion . Have you checked the clutch housing for any cracks ?
I had some broken pinions tested ages ago on a 10/41 and the metallurgist found a weakness in the pinion tooth which originated the heat treatment process ( some sort of oxidisation ) . The actual material for pinion was frighteningly strong and should never have even broken . But I did have incorrect oil in and was pretty harsh in my down changes when these broke .