915 Transmission Setup - No Shims Required ??

[mikedsilva]

I'm setting up a transmission for someone... (I don't normally work on transmissions) The box is a bit of an unknown quanity.

915/72
Bearings bores are actually nice and tight.

It needed
- replacement pinion and crownwheel (original was damaged)
- new gearsets for 2nd and 4th
- all new dog teeth, syncro bands, sliders
- all new bearings

This is the first trans I had pulled apart with only 1 shim (0.2mm).
The old pinion didnt appear to have an N number.. but the matching crownwheel had 66.63 etched on the side, next to the backlash number.. this may or may not be relevant.

The differential carrier was also pretty worn and the carrier bearing on the cover side, had been spinning on the shaft, so we sourced a replacement diff carrier.

So I'm at the setup point. I'm armed with the porsche manual, the Wiki from P Zimmerman, and also the excellent videos online by ************ (but his stuff seems to just work out perfectly every time!)

First thing I went to check, was pinion depth.
The pinion shaft (and input) was assembled in the housing, and torqued to spec so the big nut was tightenting everything down. Note, I did this without installing any shims.
For measurement, I am using a VW289 tool that I bought from Evan in Norway who also put up a thread here.

Evan had supplied it with two specially made spacers, so that when the dial gauge is zeroed, it is reading 63.30 mm.

The tool is inserted, the side cover fitted and torqued down, the tool has no axial or lateral movement.
When rotating to the face of the pinion, it is giving me a reading of 0.2mm. So I believe that means, that with the 63.3 + 0.20 = 63.5mm is where my pinion setting is without a shim.

Now, the N number on my pinion is 0.22. So that means the desired deviation is 63.3+0.22 = 63.52.

So that means, that without any shims, I am 0.02mm away from ideal spec but within +-0.03 tolerance.

What have I done wrong?
Has anyone ever come across a gearbox that didn't need any shims under the bearing retaining plates?

[Classic 911]

Hi,

Here’s something that might help you with this:

"The old pinion didnt appear to have an N number.. but the matching crownwheel had 66.63 etched on the side, next to the backlash number.. this may or may not be relevant."

[mikedsilva]

thankyou

The box is from a 3.2 Carrera so that makes sense.

[Tyson Schmidt]

If you need peace of mind, run a pattern on it.
I do that on every new setup. Sometimes the factory dimension is no longer ideal due to wear.