specs for 901 gearbox diff set up

yelcab1 · 09-08-2017, 06:55 AM

I am about to look into a 914-6 with a 901 gearbox making a loud clunk at the differential when moving from a stop or changing gear. What are the specifications for the diff set up and backlash? I assume that adjustment is via shims? Where to get those?

Matt Monson · 09-08-2017, 06:57 AM

It is scribed directly on the parts.

I bet you find a tooth missing from the pinion.

yelcab1 · 09-08-2017, 12:48 PM

Quote:

Originally Posted by Matt Monson

It is scribed directly on the parts.

I bet you find a tooth missing from the pinion.

Ouch !!!

yelcab1 · 09-11-2017, 05:38 PM

OK, update.

There was no scribe on the part that I can see. Admitted, the diff was inside the case and only the side cover was removed. No teeth are missing and it does seem to me like there is too much backlash.

What spec should I shoot for and do the shims get installed on the non-cover side or the cover side of the diff housing. If on the non cover side, then the gear box seems like It has to be totally disassembled before you can get the pinion out and then the diff out.

Trackrash · Trackrash's Garage

This is for a 911. The shims go on the diff under the bearings. Beside the ring gear being on the back side, I don't know what else is different on a 914.

Matt Monson · 09-11-2017, 07:42 PM

Ah...key technical details are confusing. My first answer was inaccurate because reading in the 911 forum about a 901 gearbox I ignored the 914 piece.

You've got an F ed up deal there. Someone took a 901 gearbox and flipped the ring and pinion to run it mid-engine. No, you won't see the specs without getting it all the way down and then it won't matter. Thats not set up according to any factory spec. Someone did that by feel and they did it wrong. You don't want this job. Its a nightmare.

Post pictures so others understand. 944s have the diff locked in like that, but not 911S or 914S. Whole thing is coming apart to do it right.

Dan J · 09-12-2017, 03:35 AM

Quote:

Originally Posted by Matt Monson

Ah...key technical details are confusing. My first answer was inaccurate because reading in the 911 forum about a 901 gearbox I ignored the 914 piece.

You've got an F ed up deal there. Someone took a 901 gearbox and flipped the ring and pinion to run it mid-engine. No, you won't see the specs without getting it all the way down and then it won't matter. Thats not set up according to any factory spec. Someone did that by feel and they did it wrong. You don't want this job. Its a nightmare.

Post pictures so others understand. 944s have the diff locked in like that, but not 911S or 914S. Whole thing is coming apart to do it right.

Sage words from a wise man Run Forest Run!

yelcab1 · 09-13-2017, 06:38 AM

It's on a 914-6 where the 2.0L engine is forward of the gearbox, which is reverse of the 911 where the gear box is in front of the engine. Therefore, to have forward moving rotation, the differential has to be flipped to the other side. You are right, this whole thing needs to be totally torn down to do it right.

Matt Monson · 09-13-2017, 07:00 AM

Quote:

Originally Posted by yelcab1

It's on a 914-6 where the 2.0L engine is forward of the gearbox, which is reverse of the 911 where the gear box is in front of the engine. Therefore, to have forward moving rotation, the differential has to be flipped to the other side. You are right, this whole thing needs to be totally torn down to do it right.

Or you can just use a 914 gearbox like the factory did... Why someone thought it was a good idea to install a 901 in a 914 is beyond me.