964 G50 mated to a 3.3 Turbo?

[Slider79SC]

Hi everyone,

Will a '90-'94 964 G50 mate up to a 78 3.3 Turbo engine. I know that I would have to modify my torsion tube and tunnel and run coilovers.

I am more wondering about the bell housing, clutch, flywheel and shifter parts of the conversion. Can I use a Harggett shifter?

Thanks.....

[KTL]

Jeff,

The Hargett shifter certainly saves you some work in sourcing the factory shifter, shift rod and coupler for the G50.

The bellhousing gets shortened, as does the mainshaft. Doing so lets you retain the torsion bar housing. Check out Patrick Motorsports way of doing it. They shorten the bellhousing and mainshaft, and modify the trans cross member to mimimize the impact on the torsion bar housing.

You use a shallower clutch than the stock G50, which is good because its much lighter.

With the later G50, you need to either modify the tail case (cut off the tail mount) and modify the underside of the case to accept your crossmember. Or you can get an early 87-89 G50 tail case.

[Slider79SC]

Kevin,

First off, thanks. I emailed Patrick's and they told me I couldn't use the 964 G50? Not sure why? And they were incredibly expensive on shortening the bell housing. I would rather modify my tube and run coil overs. Any idea why I couldn't use the 964 trans?

[KTL]

Only reason you can't use the 964 is the end case. They probably figured an end case from a earlier trans is hard to obtain. Plus the 930 chassis (is that what you're using for chassis, or just the engine?) may be such that the 964 case is hard to modify to their liking? I certainly don't debate Patrick's advice since they have done a bunch of these. The only one i've helped with is Chris Streit's G50 into his 1970 chassis.

Chris did the bellhousing modification with his local machinist, so it's not pure rocket science. Chris did the math comparing his 915 against his G50 and his works great. Just remember that the 930 chassis could be a bit different, given it's different rear suspension?

[Slider79SC]

So what I have going is I am putting a 3.3 turbo in my 1979 SC chassis, making a RUF CTR/BTR tribute. I have a good starting point with this car as far as brakes, chassis, interior so I don't want to bail on it.

I just want a better 5spd than the old 915. Is a 87-89 G50 as good as the 964 G50?

Prices seem a bit better on the 964 ones? Should I be afraid of cutting out the torsion tube for the long nose cone and using coil overs? I have no fear of fabrication as I have built several track cars with complete chassis and cage's.

Lots of questions huh.....

[KTL]

It really is the same except for the tail case. The gear ratios changed ever so slightly. Bill Verburg (go figure) recently shared some gearing details.

G50 transmission gearing question

Later on I believe Porsche refined the mainshaft for 993s to take some weight out of the trans. 964 and 87-89 are virtually identical from the intermediate case forward. Only the tail was changed to work with the revised rear suspension of the 964 with coils.

Good idea sticking with the '79 SC. Good car.... Should be able to make the 964 fit.

Some have had to cut into the torsion tube even with the regular G50. Do a search for user JohnJL or something like that. Terms like G50 short bellhousing should get you some more detail than my aging 38 yr. old memory stressed out by work, kids (#2 on the way), racecar tuning (lack thereof), home improvements (lack thereof), blah blah blah.

Don't sweat cutting the tube since even Chris had to clear his a bit and grind on the trans case (early G50). Coilovers shouldn't be a big deal for you! Just gusset the top member and enjoy the better setup of coils!

[Matt Monson]

Call Roger Brown at California Motorsports for a second opinion (and price) on the shortening. However, if you shorten it, you'll want to rebuild the gearbox at the same time. It's got to come all the way apart for shortening the output shaft, so it makes no sense to pay all the labor and not replace the wear items while you are in there.

If it were my personal car, I would probably convert it to coilovers if it's going to be tracked. It's just superior, regardless of whether or not you put in a G50...