G50 gear ratio change??

[Venetian]

How feasible is it to change gear ratios for added acceleration? I realize top end and fuel economy would be sacrificed but what other drawbacks might there be. Would accleration increase be significant?

Would this be a reasonable way to increase performance over engine modifications?

I did a search but did not come up with anything!
Thanks.

[KTL]

Heck yeah it's a feasible way to increase acceleration. It's a very simple way (intuitively) to increase acceleration. You're increasing the torque multiplication of the gears by changing the ratios. It's like increasing HP without touching the engine.

0-60 times or quarter mile times might not improve all that much (due to the earlier gear changes, which eat up precious time), but acceleration in each gear would increase without a doubt. A shorter 1st gear might not be necessary since it's already pretty quick. 2nd thru 4th, and even 5th would noticeably quicken the feel of the car.

Downside? It's not cheap. Especially for a G50. Gears are VERY spendy for the G50 transmissions- so would be a ring and pinion change.

[89911]

I replace mine (3-5) and it was the best change I have made to my car, even after enlarging the car to 3.4l and 270hp. The car is much more enjoyable to drive, either on the track or around town. The original ratios were all about fuel economy and noise elimination. My 5th gear is a 1 to 1 ratio and it is perfectly suitable ro highway use. The overdrive was simply to high for anything but fuel economy. On the track, the car comes to life. You need to shift more often, but you are seldom caught in that sub 4000 rpm zone after an up-shift and waiting for the engine to spool up. Now, ever gear change generally drops it down to 4k and the added lower torque of the 3.4 is taken advantage of. Beware of added noise with different gears, but I have not had any problems. These mostly were with cars with solid motor mounts.

[s5uewf]

I've got a few questions now that I have my transmission out and I'm ready to dive in...

My trans is a g50/01. I see the ROW G50/00 has better ratios, but still not as close as available aftermarket.

I see the G50/20 (6 speed) has better ratios, too. With the extra gear - effectively closer ratios, too.

I see" Q" and others sell new G50 gears for about $700 per gear...!

My questions:

1. Will the G50/20 6 speed fit in my 1988 Carrera? It would be cheaper to pick up an entire trans from a dismantler than to build a custom box, if so...

2. I don't think the G50/50 will really give me much better acceleration and DE performance - am I right?

3. Are there other sources out there besides" Q", offering G50 gears at lower prices than the $700 per gear range?

4. I hear setting up R&P and other aspects require real skill and special tools to avoid short trans life - is this type work best left to the pro's?

5. If I add a 45/65 or 80/100 LSD, or similar should I get a cooler?
If so, does anyone know of sources for G50 coolers?

Thanks in advance. I did search, but could not locate this info for G50 trans...

[Steve@Rennsport]

Hi:

Pehaps I can help,....

1) The 6-speed G-50 is a lot longer than your existing one and mounts differently. You'd need to make major modifications to the rear seat area, transmission tunnel, transmission mount, and fabricate new metal to cover the larger 6-speed. For a street car, its a big project; for a race car, its doable (but not cheap).

2) The G-50/50 is the larger Turbo transmission and in and of itself, will do nothing for you. Even those should be re-geared for better performance.

3) GOOD gears cost money; cheap ones are more fragile. Caveat Emptor on this phase as IMHO, this is NOT the place to pinch pennies.

4) R&P work requires the factory fixtures, a very substantial investment in parts, and the knowledge-experience to do this right. Its not a DIY'er project unless one can afford the consequences of a mistake.

5) Coolers are only needed for race cars, or those with larger motors used extensively for DE work. We build a cooler kit and plumb that into the car as required.

Just one man's opinion, of course.

[dougn1]

i'm doing the same thing to my car in the spring. there's a place in boulder called powerhaus ii (www.phii.com) that is a porsche transmission specialty shop. i got a good feeling about them based in a few phone calls. they worked up several gear charts for me and i pretty much decided what i wanted to do. my deal involves changing 1'st and 3 thru 5. the cost is about 4k for them to do it....3k if i do it. it's alot of money but i think it would be a nite and day difference.

[s5uewf]

Thanks for the feedback, guys. Steve, if I can get free I may give you a call tomorrow to discuss further.

Doug, are you making 1st gear taller or shorter?

I was thinking of leaving 1st as it is (relatively low),
making 2nd taller, 3/4/5 more overlap, with 4/5 being lower,
and maybe adding a lighter flywheel and an LSD.

Then get Steve to modify my chip to avoid stalling with the lighter flywheel...

I think I would then be able to "study driving" more effectively at DE's

[89911]

You can do that, but you will have plenty of ricers laughing at you at stop lights. True is would be better to have 2nd higher since you rarely use it at most tracks, but your sacrificing much of the stop and go driving that a street car gets.

[s5uewf]

I forgot about ricers laughing at me...hmmm. I think you have a point there.

Just seems like 1st is only used to get out of pit lane, and 2nd is only useful at entry on really sharp corners after very hard braking. It would be nice to be able to exit this sharp turns in 2nd and then shift to 3rd, rather than having to have reached the 2/3 shift point while in the turn - or shifting into 3 early and below the 4k power is available...

money is limited, too, so maybe focus on 3/4/5...

[klaucke]

$700 per gear seems downright outrageous. I've made my own gears before for a Hodaka on my Bridgeport. I would venture a guess that you could buy a whole gear hobber used for 5k easily, and make whatever gears you want! Is there a (large) market for less expensive G50 gears?

[Steve@Rennsport]

Typically, we leave 1st gear alone (on street cars) so you have a good ratio for getting the car going without toasting the clutch and change 2nd through 5th. Remember, 1st gear is machined onto the mainshaft so this is not cheap to replace.

With the right ratios, this makes a HUGE difference in acceleration.

[dougn1]

i'm making 1'st taller to reduce the gap between 1'st and 2nd. currently 1'st is lower than it needs to be. then 3,4 and 5 are shorter. i want to be at 3500 rpm at 80 mph in fifth.

i want to be able to drive at 3/4 pace and not be hampered by too much gap between gears

also i am reducing the flywheel mass. this is a 964 BTW

i would not increase the gap between 1st and 2nd. do you get into 1st at DEs?

[s5uewf]

Nope, never use first after I leave the starting lane.

I use second a lot at Summit Point. There are several corners where 2nd is really too low but using third leaves the engine
in the flat part of the rpm range. It would be nice to either lower
3rd bit or raise 2nd.

Maybe lowering 3rd is the answer as 2nd is needed for the
day to day commuting, too.

At VIR last year there was a 911 3.2 with 5th gear lowered to redline at ~130 and 3/4 lowered accordingly. That car was smoking every non turbo in the White run group by so much we thought it was a turbo, too. It left an impression seeing this car just walk away from everyone as soon as they came out of hog pen and hit the straight.

A lot faster on turn exits, too.