Rear Diff Axle Seal Leak??? And Question about Transmission Oil Change

BMW_E53 · #1 01-15-2017, 06:03 PM

Hey guys when I took my X5 to my indy last year, he stated that my car's driver side rear diff seal was leaking, but when I went underneath the car today I do not see any visible leaks and I have never seen a leak spot in the garage. Based on the pictures do you guys see any signs of a leak or past leak? (The first two pictures have flash, the last one has no flash).

Also, my car has 107k miles and it has never had a transmission fluid change and I believe it is time to change it per BMW's service manual recommendation and sometimes when I change from low speed to high speed there is a bang (pretty sure its not normal) but I have read the sticky thread and some are saying it's too late to change the fluid because the new fluid could clean and move contaminants left in the valve body and cause damage due to blockage. Also if I know that there is only 40% of oil in the pan, so how do I flush out 100% of the fluid? Should I bring my car to the indy to flush the oil and fix a leaking transmission electrical connector (even though I don't see any leaking) or could I just flush the transmission myself? Thanks in advance!

wpoll · #2 01-15-2017, 07:38 PM

That diff is covered in a fine mist of diff fluid. It's not leaking out fast enough to make drips, but enough to cover the exterior of the diff, then mix with dust etc. to make a sticky coating over the whole diff body. Not sure which of the three seals (front, left and right) and causing it but at least one of them is gone. Clean down the diff, change the fluid and watch for the leak - one location will get "dirty" quicker than the rest.

Re. the transmission, the consensus is the fluid flush (100%) will likely kill the transmission. A drain and refill (with a filter change) will change about 40% of the total fluid volume. Do a second drain and refill while later and you should have mostly new fluid in service. This method reduces the chances of crap getting into the valve body, and you can change the electrical connector seal when you do the filter change.

But it may be that only a mechatronic rebuild will fix the hard shift.

BMW_E53 · #3 01-16-2017, 03:53 PM

Quote:

Originally Posted by wpoll

That diff is covered in a fine mist of diff fluid. It's not leaking out fast enough to make drips, but enough to cover the exterior of the diff, then mix with dust etc. to make a sticky coating over the whole diff body. Not sure which of the three seals (front, left and right) and causing it but at least one of them is gone. Clean down the diff, change the fluid and watch for the leak - one location will get "dirty" quicker than the rest.

Re. the transmission, the consensus is the fluid flush (100%) will likely kill the transmission. A drain and refill (with a filter change) will change about 40% of the total fluid volume. Do a second drain and refill while later and you should have mostly new fluid in service. This method reduces the chances of crap getting into the valve body, and you can change the electrical connector seal when you do the filter change.

But it may be that only a mechatronic rebuild will fix the hard shift.

Ok so the differential is spraying a fine mist of oil while the vehicle is in motion I'm guessing.....and the indy said it was the left seal is leaking so I may just have them fix it. And thank you for clarifying about the transmission oil change, sounds like I could do it myself. What do you think about the ZF atf oil? It says it is equivalent to the Shell and is $10 cheaper than BMW oil. Also how many quarts would be needed for two drain and refills?

wpoll · #4 01-16-2017, 04:14 PM

Quote:

Originally Posted by BMW_E53

Ok so the differential is spraying a fine mist of oil while the vehicle is in motion I'm guessing.....and the indy said it was the left seal is leaking so I may just have them fix it. And thank you for clarifying about the transmission oil change, sounds like I could do it myself. What do you think about the ZF atf oil? It says it is equivalent to the Shell and is $10 cheaper than BMW oil. Also how many quarts would be needed for two drain and refills?

I've not done a fluid change myself - many others here have and can give better advice - but I understand it's about 4-5 litres per change.

If you have ZF 6HP26 transmission, you'll need to use ZF Lifeguard 6 fluid. There are alternatives but most folk recommend the ZF fluid.