looking for info on a "9M" torsen diff in my 944
 

Hi All

Have a diff marked "9M" in my 944 S2 race car. we are not sure where it comes from or who made it (other than possibly ninemeister??) and can't find any info on it. It appears to lock under deceleration which supposedly a torsen type doesn't.

Any knowledge out there?

The crownwheel bolts keep going loose on it, causing it to not bind up and the inner rear wheel starts spinning on corner exits.

Please, provide a picture. You can try using loctite blue on the ring bolts but should not be getting loose.

Thanks, I will when my guy pulls it out.

OK here are some photos:
Attachment 1262049
Attachment 1262050

I have this diff in my custom geared transaxle and was sold by Powerhauz II years ago. It is a helical type ATB. It does not really lock under deceleration. It doesn't require much maintenance either.

If the car is primarily used for DE or Racing I would change it to Salisbury clutch type LSD. I carry some in stock.

ATB? and do you mean 11 years ago? Thanks

Ah Auto Torque Biasing - somewhat like a quaife then I guess.

I'd recommend using red (high strength) thread locker rather than medium strength (blue) on the ring (crown) bolts. However, if the bolts have been cycled (tightened / loosened) more than a few times, consider replacing them with new bolts. Torque in two stages, going opposites: first stage 85 Nm, second 100 Nm. Good luck!

I'm still having issues with it not locking up - we found that the diff bolts themselves were a little loose, not much and that is fixed. My mechanic now thinks that he doesn't feel any preload putting it together so the cone washers may be weak affecting the ramp up. Anyone know how these work and /or can be adjusted?

It's a Torsen / Gleason type worm-drive, not a Sailsbury clutch disc design. So there is no preload, no cone washers, and I don't understand what your mechanic would be referring to.

Hmm - it will not lock up at all now, just spins inside wheel.... Up to 3rd gear....!!

OK, seems like this particular diff doesn't like LSD oil, or fully synthetic for that matter! We have gone back to a semi-synth 75W-90 and seems to be working a lot better. I will go back to the mineral swepco 201 that it used to have next time we do a change. With the LSD suitable oil in it it just wouldn't work.

By "LSD oil" do you mean one that has the special additive in?

yes

It sounds as the LSD friction modifier additive is affecting the LSD operation. I find that very interesting and odd as this is a Torsen differential.