Rennshift install / 901 spring pressure, Are the springs pressing on bits in the tranny? Options

[smdubovsky]

I installed the Rennshift last night. Nice piece of kit to be sure. It spring loads the 4/5 plane just like the factory shifter spring loads the R/1 plane. My question is, what are the springs pushing against in the tranny?

The stock 915 (in a 911) uses a little tab on the 5/R side to keep the springs from pressing the shift linkage against stuff in the tranny. Here is a pic from Seine systems (he makes a 915 kit that also springs load 1/2 and adds the tabs to both sides).



You can see the little tabs and the hook on the shift lever that relieves the spring pressure when your anywhere other than the center plane (3/4 in a 915, 2/3 on our 901s). The reasoning is that you can spend alot of time in 5th gear in a 911 and its putting pressure on the linkage & couplings. The stock 914's stock shifter doesnt have it, but you'd never spend alot of time in 1/R either.

What is the spring loading in the 4/5 plane doing to the tranny? Are the 901 shift fork internals that much different from a 915 (doesn't look like it in the pics I've seen)?

Just looking to keep the tranny healthy,
SMD

[lapuwali]

A minor hijack, but a related topic. One thing I'm wondering is: why spring the shifter? If you spring the gearbox instead so the shift rod is sprung to stay in the center plane, you can accomplish this much easier inside the gearbox with one spring. Alfa transaxles work this way, for example. Seems to be a better solution to me. This puts no wear on the linkage parts while it's in gear, and the various shafts inside the gearbox are bathed in gear oil and fairly hefty, so the wear rate will be very slow.

I understand by the Rennshift is made like it is. Adding the spring to the gearbox would be a much harder installation. That's not really my question. I'm just asking a general design question.