eyue

Any thought of replacing our 5 speed gear box with 993's 6 speed ? Would it fit and would also bring down turbo lag ! Closer gear ratio would makes the car more fun to drive ?

emilios

I have actually been thinking about this for some time now..any thoughts/ideas anybody?

GTgears

For what you could sell your gearbox for, you could probably do the covnersion. But the thing you need to know about a standard G50/20 6spd is that it's nowhere near as strong as your turbo gearbox. If your car is modified at all, you run the risk of destroying the ring and pinion on the 6spd. While gearsets are pretty much interchangeable between your car and the 6spd gearbox, the major strength upgrade you've got in there now is your ring and pinion. It's as big and strong as the current GT3/TT ring and pinion.

That said, something that has been a popular improvement to your gearbox for a number of years now is to find stock 5spd NA ratios from a G50-01 or G50-03. Your gears are in no way stronger than the NA gears. They are just taller. Putting in some racer's takeout good used NA gears that you can buy on the cheap and installing them in your gearbox will get you shorter closer shorter ratios without spending the $1100-2500 a gearset it costs to buy new gears, and lets you keep the bulletproof ring and pinion that's in there now. At the end of the day, more gears is not always more...

kojo911

here's another thought. If your biggest concern is turbo lag, why not spend the money you would have spent on the transmission swap on an EFI set up? Don't know what the smog rules are in HK but the cars drive much much better when switched to efi from cis

jeff91C2T

Having done what is suggested below I can say I'm pretty satisfied with the results. I installed 2-5 gears from a low mileage 03 box. 2nd gear tops out at 67 mph and 5th at 165 mph (going from memory here). Pretty good split for autox and track.

Keeping the G50-52 in place makes sense as it has the stronger 1st gear and r&p.

Geoffrey

It has been my experience that the 5spd works better with turbo than a close ratio 6spd, especially if you replace the ratios with the N/A ratios. This is especially true if you have an EFI modded high HP turbo engine that has a wide torque band.

eyue

Thanks for all the response guys ! I just thought that a 6 speed for my stock turbo would be more enjoy around town plus a little track fun days !

GTgears

The 993 Turbo gearbox can be converted to 2WD and does have a strong ring and pinion. Though IMO it's not really an upgrade. The 6spd 1st and 2nd gear synchros are more delicate than the ones used in the 5spd gearboxes. If it were my personal car, I'd regear it a little bit and call it good enough.

eyue

What do you mean by gearbox convert to 2wd, I thought all gearbox are the same !

GTgears

993, 996 and 997 Turbos are AWD vehicles. You've got the last generation of 2WD turbo cars from Porsche. In the long run I personally think that it's going to be one of the more collectible cars from the early 90's. To me, keeping the original gearbox, but regearing it, is going to help maintain that collectability status.

Jean

I used to have a 4WD 964 3.6 T with a 993TT gearbox fitted by Autofarm in the UK. It was not an easy job but it ran great.

I would not go through the conversion, as taller gears are great fun for a turbo car. Where you will gain will be in acceleration within each gear, due to running higher RPMs at same speeds (less lag) and the engine to wheel torque conversion itself, but doing a 0 to whatever speed won't make a difference.

In case you do want to do it, I see no downside in putting a G50/20. True that they are not as solid as a G50/52, but they are definitely solid enough for any street driven turbo and can take enough abuse. As a matter of fact I have an old G50/03 fitted on a 500+hp twin turbo car for 10 years now and never had an issue.

And as has been said above by Geoffrey, I disagree with modifying the gearing (shortening) on any turbo engine, the engine has plenty enough power to offset any shortfalls of a few RPMs early on acceleration. I have always looked at ways to have taller gears, mainly 1st and 2nd. Definitely not worth the money IMO.

No matter what, don''t sell your G50/52.

Vince964T

I did the swap with a 993C2 gear box. You are right I sold my 5speed tranny and it paid for both the new gear box and the work to fit it.

It does improve engine response a good deal and is a good mod for a track car.

However I did the switch now 5 years ago if I remember correctly and this year going from 1st to 2nd isn't easy anymore when the car has been parked for a long period of time ! It gets back to normal after warming it up. Who knows, may be the original gear box would just work flawlessly

If I had to do it again I would do better research and modify the original gear box for track use. For both street and track if you really like high speed and want reduced lag the 6speed isn't a bad option may be.

GTgears

Your post is somewhat self contradictory. You tell him not to put the NA gears in his 5spd but then post that you've got a G50-03 5spd NA gearbox in a turbo car. You've got what we've told him to consider, but you tell him not to do it.

Furthermore, you cannot compare a G50-03 5spd to a G50-20. ALL of the 5spd G50's are stouter gearboxes than the G50-20. Just because a G50-03 can take it does not mean that a G50-20 can.

Jean

Might be..Let me clarify..
I bought the 1974 car with twin Garretts, twin plug, pressure sensing engine, and the G50/03 as is, only with a modified 935 clutch.. I did not modify it myself. I am telling the OP that I wouldn't do it, because I saw no benefit in performance that could be worth it in moving to a 6 speed vs. his 5 speed. Hope it is clearer.

The only benefit would be in acceleration "within" a certain gear, elasticity in other words.

Of course I can compare. Not sure what you mean by Stouter?

The G50/03 and G50/20 have the same gears strength and are both rates at 300NM if I am not mistaken, except bellhousing modifications, different gear ratios, better airflow to the center of the clutch and a provision of twin cone synchromesh for 1st and 2nd gears for smoother engagement.

If I can use the G50/03 without problems, he can use a G50/20, and I have in the past. True they both have smaller diameter crown & pinion than turbo gearboxes but that does not seem to be a serious problem. I might not build and sell gearboxes nor have your technical experience for sure, but I have practical driving experience and tested on the street and raced numerous gearbox/engine combos for many years, including G50/52, G64/51, G64/20/21, G50/03, GT3RSR, and Ricardo sequential gearboxes on my turbocharged cars.

Net net to the OP, I would not do any changes whatsoever to the gearbox on the 3.6 turbo, neither replace the gearbox, nor change the gear ratios. Should you want to change to a 6speed, the G50/20 is a well priced alternative............IMO.

GTgears

Maybe "stouter" is the wrong term since there's not really any size difference there on the individual components. All I am saying is that over the last decade I've seen a lot more G50/20's fail when faced with turbo power than G50/0X (where X=00:05 5spd boxes). And when they fail it's almost always the ring and pinion on them. Maybe it's oiling. Maybe it's a difference in the casting of the cases. I'm not really going to speculate why. I just know that 5spd G50 NA boxes in practical terms appear to be stronger than G50/20 6spd boxes. One can take that FWIW.

As for the rest, you are entitled to your opinion. I never came in here posturing claiming that I am the one and only gearbox expert in the world and that everything I type must be taken as transmission law. Your original post just wasn't very clear to me, and thus the comments that were meant to elicit further clarification on why you feel the way you do about the gearing and/or gearbox swap question. The OP can draw his own conclusions from all of the opinions set forth, and decide what he personally thinks is a good solution.