NJ-GT

After evaluating all the alternatives, including buying an used GT3 Cup car transmission and keep mine as a spare, the best deal for the money is:

- Install 4.00:1 Ring and Pinion gear from GT3 Cup.

The following figures are for the Stock GT3 Tranmission on MPSC 295/30R18 (25.2" diameter). Redline estimated at 8200rpm 1st-4th, and 8000rpm 5th & 6th. (my car goes 8350 in 3rd ):

Ratio Max Speed
3.82 47.00
2.15 83.00
1.56 115.00
1.21 148.00
1.00 174.00
0.85 205.00 (it doesn't go this far)
3.44:1


GT3 Cup Transmission with MPSC and Michelin 27/68-18 (26.77" diameter)

Ratio Max Speed
3.15 49 / 52
2.00 77 / 82
1.56 99 / 105
1.31 117 / 125
1.09 138 / 146
0.91 165 / 175
4.00:1

The modifed GT3 transmission with Cup 4.00:1 gear instead of stock 3.44:1.

Ratio Max Speed
3.82 40 / 43
2.15 71 / 76
1.56 99 / 105
1.21 127 / 135
1.00 150 / 159
0.85 176 / 187
4.00:1

0-60mph, 0-100mph, 1/4 mile, autocross powerband and track powerband should be greatly improved with this mod.

Now, I need to find out where to get the 4.00:1 ring and pinion at an affordable price, and a shop in NJ to do the installation.

cosmos

Let us know how it goes.

DCLee

You're going to wind up with a very short 1st and 2nd.

Re getting the LSD at an "affordable" price-- Porsche Motorsport does not seem to have this word in their dictionary.

Lee in D.C.

Greg Fishman

Do a search on "Brian Copans" he is the only one I would trust to do the job right. Also he is likely to have many of these R&P's around.

NJ-GT

Exactly. I need that 1st and 2nd gear for autocross. 3rd-6th for track events. It will be fun to be able to use 6th at WG, Pocono Full and VIR.

I will. Thanks a lot. That's exactly what I'm looking for.

GrantG

The heading of your post says - "close ratio". Just remember that you are still going to have larger than desired rev drops between gears by just changin R&P. I considered doing that with my 993, but it doesn't really solve the problem. Changing the individual ratios to suit your needs would be much better (but pricey). Granted, the ratios are closer than the 993.

I can email you a spreadheet that will allow you to graph your gearset and see what the rev drop is for each shift point if you email me at: grantg10@aol.com

Sun Ra

grant is right. and those stock gears are so tall

i miss the 70-73 s/rs days when gear and gearbox changes were just a couple $K. to regear 2-6 in the gt3 box is $$$$$$$$$ and you never get it back, so i bailed on the concept.

GrantG

Watt - getting a gearset for a 73RS is no bargain either. I'm looking at doing it now and it won't be cheap (over $5k, including LSD and general rebuild stuff)...