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Smart quod bastardus
fredmeister's Avatar
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,229
rear diff ratos for 930 4 speed

What are the different rear axel diff ratios available for the 4 speed 930 gearbox?
I have the stock ring and pinion of 9/38 or 4.22 to 1.
I am interested in getting more response and acceleration form the engine with the least amount of expense. This would mean a diff change but I am not sure what is available in terms of gearing that would be lower than 9/38 gears.

Anyone know what else is out there?

1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 11-09-2007, 12:48 PM
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Join Date: Jan 2007
Posts: 1,077
Bruce anderson has a book "porsche 911 performance handbook second edition" which lists all the possible gears available for the two ring and pinion types that people run in the 930.

It is basically a page chart for each ring and pinion, listing the individual gears and what speed and rpms you would be running. There is a wide selection.

I would buy the book used at Amazon just for that info, nevermind that it is a good book.

If you switch to the 5:1 final drive ring and pinion, like my car, you will have insane, nasty acceleration in 2-4 gear. Take off like a rocket booster in 4th on the highway.

But your top speed will be a little over 150 mph, which isn't a big deal for most of us.

The real problem is that 1st gear becomes useless, it winds up to about 42 mph, so you have to redline it to really get into the meat of the power in second gear. The solution is to run a higher 1st gear and the other gears you can leave alone if you go with the different ring and pinion. 51 mph would be perfect.
Old 11-10-2007, 08:02 AM
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