ROBinGa

Had local quick lube do oil change and also do rear differential fluid change. I have 122,000 on truck. Pretty sure last differential service was by dealer at about 75 or 90,000. When they got to the back the tech asked if I had noticed any issues and mentioned there was fluid leak evidence on driver side inner wheel and tire. They said differential was overfilled since when they removed plug, fluid was gushing out and was above fill line. Said it had been overfilled by someone before and probably the cause of fluid leak on inner wheel and tire. I asked how fluid could be above fill line of drain plug - they said pumped in above fill and plug inserted quickly. They said the pinion wasn't the leak which was good news but that means nothing to me. They said should not be an issue and was because my diff was overfilled. So they refilled my differential with valvoline synthetic to proper level and I drove about 5 miles home. No issues but not much of a drive yet. How can a differential be overfilled and if not how can some other fluid be getting in there? I have never towed a boat to have backed into water or anything like that. Would an overfill really weep fluid at the wheel end of the rear end? Any ideas to what's leaking?

BassAckwards

I'm with you on not getting how you could overfill it that bad unless they decided to put all the fluid in through the breather hole.

No idea.

sdmartin65

The axle has a seal on either end where inner axle shaft goes in. A small leak there is not a big problem. If leak gets worse it can get on brake pads and ruin them. It's just something that goes out occasionally not the fluid level in the axle causing it. Sounds like them talking about a subject they really don't understand and just causing confusion.

ROBinGa

Thanks SDMartin I've been reading up on this since getting home and I bet you are right that my axle seal on that side is gone so looks like I just wasted the money on the rear fluid change since that seal needs to be replaced and fluid has to come out for that. Might as well change both seals huh?

sdmartin65

Both seals yes as there is some disassembly just to do one.

jamie930

I would do the wheel bearing to while you are in there the bearings are cheap and only take a few extra min to do