Last winter I pulled the entire rear suspension out to replace all off the rubber bushings with urethane. Since I had pulled the diff out, I went ahead and cracked the fill and drain plug and refilled it while it was out of the car. It never leaked before this. After everything went back together and I started driving it, it started leaking. I had overfilled it and it was blowing out the top vent. So, with the car in the air and level, I removed the fill cap and about a cup of oil drained out. But, even after that it continued to leak all summer long. Nothing terrible, maybe an occasional dime to nickle spot. So could I have damaged the axle seals by overfilling it, or is it still just blowing out the top. I have it high in the air right now doing a transmission swap, so now might be the time to do something. Any suggestions? 

You need to clean the diff better so we can see where it's leaking. Use some brake cleaner and a rag. Then check it after you drive it. It could be a side seal(s) from the looks of it but it's hard to say for sure. Could be from the vent tube.

 

Chuck

I'm waiting on the Red Line MT90 fluid I ordered from Amazon to show up so I can complete the Transmission swap that I'm doing right now. But then I have to wait for the snow and salt to go away before I can hit the road and test anything. I think I'll take your advice on the brake cleaner when I can drive this later on, and just let it go for now. 

 

Thanks

FWIW. My diff wasn't leaking, but I was on the hunt for thumps-and-bumps, so I did the seals in the process. Datsun 240z replacing oil seals r180 differential.

'71 240Z

WoodWorkerB.com

Edited March 7, 201511 yr by bvolken

Can't se much on the photo. You need to clean it as best as possible, take it for a run, get it nice and warm and check it again.

My drain plug was leaking until I used sealant on the threads.

It was probably leaking because I didn't want to over tighten it. They can be a pita to get back out.

Chas

Overfilling will blow out your seals and your diff will be smoked.............FWIW..........fill to the (bottom) of the top fill plug..........nothing more - nothing less.