Thread: what tranny
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TurboKraft TurboKraft is offline
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Originally Posted by kevinbodman930 View Post
Chris,do you think I should replace 2nd,3rd on my 78?or go with a g50-52?
Easiest and least expensive: change 2nd & 3rd to ratios that suit how you drive. Sure, it's a full disassembly of the transmission, and you'll likely find some worn parts that are prudent to replace at that time, but it's the least expensive and shortest path to quickening the gearing.

More expensive and complicated: shortened 3.2L Carrera G50 5-speed
We aren't fans of doing a G50/50 swap because of the super-tall Autobahn gearing. The Carrera gears are just about optimal for street / canyon carving / highway blasts / occasional DE -- in other words, how most of these cars are driven.
If you need a taller 5th, install a Turbo 5th gear.
As a plus, you the superior G50 (BorgWarner) synchronizers for better shifting, and hydraulic clutch actuation as well.
So you have to source a complete 1987-89 Carrera setup: transmission, pedal box, shifter assembly with shift rod.
Then fully disassemble the transmission to shorten it -- and inevitably find parts that need replacing.
And install a LSD, as most were open diffs, and those that weren't are usually worn out by now.
And weld transmission mounts into and 1978-86 911/930 chassis.
And usually modify the transmission mount.
And modify the shift rod and/or coupler.
And install all new hydraulics, because a person would be crazy to install 30-year-old components.

The result is awesome, but with the parts becoming increasingly scarce, it's also becoming more expensive.

I'd evaluate the car after it's finished, get some miles on it in order to best determine the gearing that suits you. After all, a gearbox is functionally just a torque multiplier, and when you have a lot of torque, you have less need for shorter gear ratios. You may find you enjoy the standard gearing.
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Old 03-18-2018, 04:10 PM
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