TrueTrac Issues..?
 

I've got a Detroit TrueTrac in a Moser 9" and have just over 600 miles on it. Pulled out of the driveway and started hearing a slight rubbing sound (like a tire rubbing on 1/3 of its rotation) when car gets over 5 mph. Fluid is full and have isolated the noise to the differential. I read some other posts on the web about TrueTrac bolts backing out etc... I bought the car out of state and didn't due the install so am not that familar with TrueTrac's. Was wondering if anyone else has had any issues with a TrueTrac or if there were any gotchas on the disassembly / re-install before I tackle it.

Thanks in advance for any advice.

They don't recommend synthetics so you may want to dump the fluid first and change over to Dino 80w90 to make sure.

there's also an additive to put in after the oil, you do have to make sure the pre load is set on the third member.

Least according to Moser they said no additive needed, nor should be added.

To diagnose this a little further... and to be sure that it is something in the center section...

Jack it up, put it on stands, pull the wheels and tires... re-install the wheel nuts to bolt the rotors/drums to the axle. Have you/someone start it up an re-create the load that was producing the noise, while you/someone uses a stethoscope to pin-point the noise.

If its not in the brakes, pull the rotors/drums and do the same thing. If its in the third member... pull it out and look for anything obvious. If not... and you are not comfortable with doing the work yourself, I would recommend that you take it somewhere that specializes in differential service to pull it apart, fix it and re-assemble.

Seeing that you live in in Arizona... I would recommend that you use a straight weight 90 at the minimum... (I myself would use a straight weight 140.) If you can get Schaeffer's locally, I would use their #209A with the suspended moly... or if a multi-viscosity in being used (or you cant find the Schaeffer's, there are dealers in Mesa and Phoenix)... I would use Torco's 85-140 RGO (available all over Arizona.)

Do not use a synthetic... use a crude or paraffin based oil product and no, as stated... you do not need to use any friction modifier.

Problem solved... Thanks Everybody
 

During the disassembly I realized that it was the rotor dragging on the calipler due to a small amount of play between the rotor and axle shaft. Adjusted the caliper and voila! No more noise. Needed to replace an axle seal and differential gasket too so all in all it was a productive exercise. Regarding the diff oil for the TrueTrac you are correct that no additive is needed as there are no clutches etc..

Thanks again!