daypass72

I bought my 04 screw 4x4 about 6 weeks ago. I decided to change the rear diff oil since I have no idea if and when it has been done. It had a slight howl under acceleration. I drained the oil and it was very dirty. I cleaned all the inside with brake clean and filled it up with 75W140 LUCAS Synthetic oil and Ford friction modifier.

Its been a week since I changed the oil and and its alot worse than before. Any ideas why? Is this oil ok? Or should I have used a different brand?

Thanks

hype6477

i am no mechanic so i am not the best to answer this but the fluid is mixed its not pure sythetic its like a 50/50 plus the ford friction cream

hillbilly25002000

spraying it with brake kleen may not have been the best as it dries everything up

UnleashedFord

ill ask my dad about that since he is a mechanic but i dont think that was a good idea with the brake cleaner

Man Truck

I can't imagine brake cleaner did it any favors, but I think your biggest problem was the SYNTHETIC OIL. See when you use regular oil it builds up gunk in the corners and crevices everywhere. When you put synthetic oil in, it is a much cleaner oil and will break up those gunk deposits, and will circulate all those chunks through the gears and whatever else is in there causing damage. Just like in your engine. If you start your truck with Synthetic, great stay with it, but don't go back and forth. I would change it again VERY soon and put regular oil back into it.

I am NOT a mechanic but I did stay at a holiday in last night. I hope this helped.

BUZZFX4

If everyone thinks that useing brake clear is a bad idea. Then what would be a good product to be used to clean out a diff that has had water or mud get into it?

Man Truck

Not sure, I don't know exactly what break cleaner would do or not do. I would think if you put oil back into it, it wouldn't matter, I just don't know. I just know that going from Regular oil to Synthetic isn't good.

trickster

I'll take a stab and say deseil fuel or kerecene.

driver444

How many miles are on this truck? Has it towed alot? I hate to tell ya, but if you're getting a howling noise (specifically), fluid isn't gonna fix your problem. Howling is a result of either worn bearings, worn gears, or an improperly set up rear end, which will eventually lead to the other 2 things I mentioned.

As far as the fluid being really dirty... Limited slip differential fluid will over time look a little dirtier than fluid in an open diff because of the friction material (clutch material) that ends up in the fluid. But It shouldn't be BLACK.

As far as the brake cleaner, you can use it to clean out a differential. I would only caution you that it does a nasty job on plastic and rubber (I.E. axle and pinion seals) As far as the gears and bearings, it won't hurt anything.

thump

I don't think synthetic is the culprit. When I regeared I switched both differentials to Royal Purple Max-Gear (full synthetic) and both are silent. I think you have a mechanical issue (like a poor lash adjustment or excessively worn gears) and the new oil has just made the noise more evident now that the sludge is gone.