I posted this in the B-van section, and get no replies so lets try it here. It's a general question. I have a long trip to take and my rear diff is kinda noisy. It was all rebuilt about 30k miles ago. Its a 1 ton 2wd, I believe Chrysler rear end. Anyway, Is it okay to use Lucas in a rear diff? I used it in an engine and it foamed terrible. I know these kinds of threads can take off with repair or replace, but that is not an option at this time. If lucas isnt good , is there something I can use ? It's not howling or screaming , just has an audible whine about 70 mph

 

synthetic 75w90 will work or if towing a lot, go to 75w140, as recommended for the chrysler 9.25 differential. I wouldn't put Lucas in there if it was free. Could be the pinion bearing and fluid won't fix it.

 

Lucas foamed up?
Your joking right?
I've used Lucas for many years. Maybe you grabbed the dish soap.

Why would you use it in your diff if it foamed up in your engine? If it happened to me I'd stay far away from it as possible. Not buy more.
I'd also contact Lucas and tell them their crap is chit.

Yes, you can use Lucas in your diff. Unless you have a L/S. Will it work? Cant say.
I'm in agreement with the others. Do an oil swap and hope for the best.

Old school fix. A handful of sawdust quiets things down for a couple weeks. Best if your selling the truck. Diff will be shot.