Hi all,

I changed my rear diff oil the other day beacuse while at an oil change place the guy got all dramatic on me about how my rear diff oil was sludge and needs to be changed right away, making it sound like the sky was falling; or at least my diff. He tried to sell me on getting it done there but, well, no.

Having a long drive ahead of me the next day, I figured I should check for myself. Pulled the plug and didn't find any menacing sludge trying to kill my diff. Decided to change it out anyway to be safe and to have a look inside this diff for the first time. The oil was clean as could be, maybe a bit foamy, but no big deal.

I used about 2.5 bottles of Quakerstate synthetic 75W140. See link below. I was unsure though if I should use a friction modifier or not since the label on the oil bottles said it was for limited slip diffs. I decided to use some FM anyway (4 oz).

What I notice now though, is that while driving in a parking garage at work, the inside wheel used to always break loose in a turn and slip with only very slight throttle. Now, since the oil change, it doesn't. It will still posi up and spin both if I come onto it, it just doesn't seem to do it as easily. Does this seem right? Could it be there was already a friction mod in the oil and now there is too much, or do I worry for nothing?

Any thoughts?

TIA!


http://www.jeepforum.com/forum/f250/...ear-oil-771851

 

Sry I cannot help you out with that. Maybe someone will sneak in with an answer

 

Does the oil say if it contains any friction modifier?

I wouldnt be too concerned; worse case senario too much friction modifier in the gear oil you put in would just make it like an open diff.

If it didnt have any friction modifier and the gear oil didnt contain any, then you would have some trouble. Sounds like you should be ok though. You would experience a lot of chirping with just gear oil in the limited slip diffs.

 

Thanks anyway Eimer. Appreciate it. I guess to be specific, my questions are:
1- Can you put too much friction modifier?
2- Has anyone experienced noticeable differences in posi function after an oil change?
3- Does oil stating it is for limited slip differentials still need the FM additive?

 

No it didn't say so specifically which is what had me confused, but it did say it was good for limited slip diffs. The parts guy said I didn't need FM which didn't help my confusion, but in the end I figured it can't hurt. The only reason I'm questioning it is because the LSD does not "seem" to posi up as easily, although it still does.

You're probably right. I guess I was more concerned that added slip being hard on the clutches. Maybe it didn't have any FM in it before and that's why it was more "sticky" around corners.

Thanks!