38D

I think Geoffrey is right on with 165. I would hit ~152 in my D stock '91 turbo at the Glen. With 400hp and 2300#s, you should be at least in the high 150s at MO, if not low 160s.

Gary R.

That's what I assumed... The shortened G50 i'm being offered is going to be expensive to start with, it currently has short 1-4 and a tall 5th. I may try it as is and see if I can live with it.

Larry Herman

Gary, the last thing that you want is a big step between 4th & 5th. Your car will fall flat on its face when you make that shift. The stock 5 speed G50s are actually pretty good 3-4-5. It's the 2/3 shift that kills you. BTW - Happy New Years! Watching the Eagles win their last regular seaason game was enough excitement for us!

Gary R.

Happy New Year to you and your family Larry!

I'll talk to my guy about the ratios before dropping the G50 in. I have plenty of other work to get done on the car to get it ready for track time and still haven't gotten started on my SC yet!!

38D

Gary, is this a G50/52 from a turbo? If so, you want a taller 2nd & 3rd, and a shorter 4th and 5th. And you definitely do not want a taller 5th. 5th in my turbo is basically a useless gear, as you don't get to it until 150ish. If it is a
G50/03, make sure it has a LSD in it (all 50/52s came with LSDs).

If it were me, I'd do the following:

1: 2.333
2: 1.632
3: 1.269 (stock G50/52)
4: 1.040
5: 0.868

Gary R.

Colin, I honestly don't know. All of this came from a 30 minute look at car/talk with Dan Jacobs and is totally up in the air at the moment depending on how the car checks out. I really appreciate the input on the gearing/tranny model as my guess is Dan is reading this and will fill me in once we talk again (hopefully tomorrow).

purplehaze.

Gary -

I'm contemplating closer gears on mine as well.

If you want to check the "feel" of a stock G50/50 with LSD you can drive mine. TALL gearing, nice for WGI but not LRP. I never use 5th at WGI, just wind out 4th before the bus stop.

Colin - your input is useful as always, and Happy New Year!

Does anyone have approximate cost for the gears and the swapping, assuming the gearbox is already out of the car?

Thanks,

Glenn

38D

The G50/52 is stronger than the normal G50/03. The 50/03 would probably work fine for a lower hp turbo car. But if you ever plan to start pumping out more hp, the 50/52 is a beefier unit.

For gears, you basically want to set redline in 5th ~5mph over your expected top speed. I chose 165 based on my experience in my car. This 3.3 you are looking at should actually be faster than my car as it will not need to meet a minimum class weight and will have these shorter gears. So at the Glen, I would think that high 150s would be very realistic. Then, you want to make 1st usable. In my stock 50/52, I run out of revs in 2nd in th toe just past the apex (so I normally just stay in 3rd). Raising 2nd by ~12mph would make it about ideal. Then gear 1st so it is taller and can be used in real hairpins like at Sebring.

Now, the downside to all this is that you will shift a lot more. In order to make sure you are actually faster, you'll definitely want a LW flywheel & race clutch. And you'll need to get really good at doing 5-4-3-2 downshifts very quickly.

Gary R.

The good thing is i'm used to keeping my car above 4000 RPMs at all times now so the transition shouldn't be too horrible. I use 3-5 at Limerock and at the Glen in the SC but only top out at approx 130 or so (I run out of room way before I run out of RPM).. As far as weight, Dan seemed to think 2500LB is possible so she should cook right along.. considering my SC weighs 2550.

38D

Gears are normally $250-$500 each. Plus install. And then you'll do the "while you are in there" stuff like new synchros.


You actually don't have to keep a turbo above 4000 rpms. In fact, one of the best things about turbos is that they makes tons of torque down low. What you will notice is that big of lag (I hope this car has a K27-7200...if not, you'll want one...). What will be different is that you won't be able to do much throttle steering, which will likely make you a better driver anyway. You have to plan ahead, then put the pedal down and keep it there. I never LFB'd in my car, though I was thinking about starting.

My car weighs in the high 2800s with no ballast, but it is the heavier (and stiffer) 964 chassis.

JoeMag

For what I've mentioned above 400hp norm asp, 2300#, should I be looking for G50/50 or will the other less beefy ones work fine for me? Dedicated race car. ...I plan on trans cooling too.

38D

You probably would be fine with a 50/03, but the 50/50 or 50/52 certainly wouldn't hurt. It's really torque that destroys a trans, not hp. In a NA car with 400hp, you are probably only going to be around 320-340 ft lbs of torque. That would be fine for a G50/03. A turbo of the same hp would likely put out 390-410 ft lbs.

I would probably go for a 6 speed 993 G50 unit for this car, with some shorter gears.

JoeMag

Colin -- Are there differences in the G50 6 speeds as far as beefieness? Also, thought I recalled reading something that the first gear is made part of the shaft? Is that correct?

38D

Yes. There is the normal 6 speed G50 as found on the NA 993s, and then there is the ulta beefy GT2 trans, which is basically a 2wd version of the 993tt trans. Rick Deman is the guy to talk to about a GT2 tans.