Oops, friction modifier added

[sag2]

I stopped by a Jeep store to see a buddy before Christmas and since the service department was real slow I decided to have them change the oil and filters, and service the rear diff. The technician added friction modifier because he assumed (Jeep does not use AA) it was needed for anti spin. Well when I got off the freeway and made the first turn the rear end shuddered like crazy. It really chatters when hot, but is not noticeable when cold. Got back from Portland, Seattle and the Tri-Cities with lots of snow time and need to change the fluid again.

Picked up the new 04 last night, so I may not worry about it, except the new owner might think the anti spin is shot and try and have it rebuilt.

 

[rbattelle]

Why would friction modifier cause your limited slip to slip?

 

[sag2]

It is not causing it to slip, it is binding up from too much friction on the clutch. The chatter is the unit trying to slip on a turn.

 

[rbattelle]

Hmph! I thought there was no effect from adding the friction modifier to the rear. I guess I was wrong.

 

[JHardwick]

I didn't think the AA had clutch packs like the Dana ... ..... guess I was wrong too Ryan.

 

[rbattelle]

Oh yeah! There are no clutch packs in there. So what the he!! is slipping, sag?

 

[sag2]

My memory is not that great, but at the training center I think they said AA used a conical clutch rather than clutch plates. If I recall about 20 years ago the light duty Dodge limited slip axles used the same type of setup. It appears that the AA axle can handle much more torque than the old clutch-less diffs.

 

[rbattelle]

According to the service manual, page 3-145:



"When one wheel begins to spin the pinion gears on that side are forced toward the pinion brake shoes. The pinion brake shoes cause frictional drag on the opposite pinion gears and the side gear. These friction forces transfer the power to the opposite wheel. Once the friction forces are overcome, differentiation will occur. The torque will be continually biased by the frictional forces to the high-traction wheel"



I find this explanation a little confusing, and the diagrams in the service manual don't help much. Perhaps someone smarter than me can enlighten us?