Rear differential issues. Advice needed.

[djbonsu]

As some have already stated, im pretty sure what you are hearing is the LSD engaging and disengaging. I have a Tru Trac in the rear and experience the tire chirp at times while turning. I would still check the fluid to make sure there isnt any metal in it.

[wahoo]

I too had this diff. clutch chatter a few years ago. Drained the fluid and found nothing unusual in it. Replaced with synthetic 75-140w that supposedly had friction modifier in it. Still had problem, added bottle of friction modifier, still there, then another and out of desperation a 3rd bottle. Finally noise went away completely. Bear in mind I drove a couple of thousand miles between each bottle. At the time I had no idea others were having the same problem.

[BK8LST]

We just had differential work done on our Ford van Sportsmobile. There was a loud clunking, especially on acceleration and the seals and some other stuff in the differential was bad. Luckily, we had a way to get the job done at my college automotive department, but parts were about $500.
Best of luck!

[Mr.Anderson]

Any recommendation on the type of friction modifier to use?



I just had the front and rear differential fluid swapped out as a preventative maintenance step couple weeks ago and am experiencing what feels like a front end rumble when making a turn from stop (traffic light, pulling out of gas sation, etc.)



My mechanic said he 75W-140 in the front diff and 80w-90 in the rear both full synth.



Wondering if I should have just stuck to the "if it aint broke don't fix it" mentality there but too late late now.

[Twoxentrix]

l always use Amsoil's slip lock
https://www.amsoil.com/p/slip-lock-adatb/?code=ADATB-EA

Curios though about the recommendation to use a different weight for the two axles??? I've always used the same AMSOIL SEVERE GEAR 75w-140 in both

[Mr.Anderson]

Thanks, I'll have to see if I can get my hands on some of that amsoil.



I asked him about that too and he said since the front diff is typically only going to be engaging during off road and lower speed operation under higher load the higher weight oil is better. I don't know enough to argue otherwise but he said he uses the same oils and combo of weights in his F250 truck.

[carringb]

Correct that high load is better with heavier oil.

I run 75w-140 in my rear diff. There’s zero benefit to running 80w-90 back there. Especially since that’s not a typical synthetic weight. It’s probably conventional. 75w-140 has to be synthetic.

I could see running 80w-90 up front simply because it doesn’t get much meaningful load and conventional is cheaper. And usually needs to be drained for moisture long before the oil breaks down.