Ring and pinion gears., Gear ratios. Options

[Keith914]

What are the practical (including cost) options to change the ring and pinion gears to "lengthen" all the gears so as to optimize a more powerful engine?

[Dave_Darling]

If you have a 915 gearbox, there were a couple different R&Ps to choose from. The early ones had a 7:31 like our 901s do; the later had something like an 8:31?

The cost for a different R&P in a 901 box would be astronomical. And it would take time to find someone who could manufacture the gear set for you.

The easier way to go is tires with a larger overall diameter. Most often done by going with larger-diameter wheels and not dropping the aspect ratio (sidewall height) of the tires to match. That effectively makes all of the gears taller.

Or change over to a 915-based transmission. Or some other trans.

--DD

[Chris914n6]

The easier way to go is tires with a larger overall diameter. Most often done by going with larger-diameter wheels and not dropping the aspect ratio (sidewall height) of the tires to match. That effectively makes all of the gears taller.

--DD

This. I stepped up to stock 205/55-16 Boxster wheels & tires.

2nd is machined into the shaft so can't do anything with it. As such changing first is near pointless, plus it sits on a smaller unsupported section of the shaft and snaps easily.

I have a 3.0 so starting in 2nd is easy, and nice around town as I don't have to shift as much. 3 and 4 are good city gears. Flipped H 5th for highway cruising at 3000rpm. With the Boxster tires that's 90mph (IMG:style_emoticons/default/biggrin.gif)