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rear differential leaking

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52K views 21 replies 15 participants last post by  325xi2004  
#1 ·
I took my car to fremont bmw and took a look at the underside. The mechanic said there is a rear differential leak and need to take it apart and replace the parts etc... here is the pic I saw under the car.

the parts and labor is like $1300. I am not seeing any leak where I park my car. but it is definitely showing a leak there.

any advice?
 

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#5 ·
Looks like a leak from the input shaft(as the output shafts look very clean), probably a bad input bearing or a seal.
Anyway, $1300 is WAAAAYYYY to much money for this. A brand new diff isnt even that much.
If you dont have much time to spare, you should just buy a used but good diff, even on this board, for like 300-450 and replace it, then look into the old one. If you have lotsa time to spare, you should take it out and replace the bearing yourself. See for yourself, but whatever you do, DO NOT pay$1300 to anyone for that job.
 
#13 ·
yes looks like the front input shaft seal. this isn't that easy. but like you've heard the whole diff needs to be taken out and then put back in after the seal changed. but for 5hrs of labor x $120 hr that's only $600. so where this dealer is charging you another $500 for parts is :dunno:

you have a zhp and from the cover it appears to be a manual so a 3.07 ratio. you might if you want more performance consider a used lower diff ratio(higher number) which on a 6 speed works well. it will be much cheaper overall and most indy shops can do it for around 3-4hrs labor.
 
#14 ·
This is why people don't buy these cars because they pay these retarded prices for sh!t. You have a ZHP and hopefully it's a 6spd. Do yourself a favor and buy a used diff (3.38 or 3.46) and DIY. It isn't hard. I did mine (3.38) in 4-5hours. Total cost with my trade in of the old diff to the junkyard.........................$75!!!!! And it is faster and more responsive. Just DIY and tell them no thanks.
 
#18 · (Edited)
member Countdownbmw has a listing for some in the Classifieds-'Engine & Performance' section. He ships at a low cost too. The 3.38 will have the larger flanges so you don't need to swap anything.
 
#16 ·
just check ebay. Just do a search for bmw 3.46 or bmw 3.38 and they will pop up. I found mine on ebay but realized the shop selling it was 10 miles from my place (doh) so I went there and was able to buy it for $175 and then return my 2.93 unit for a $100 credit. Now that was luck of course but you should be able to get one shipped to you for under $300. BTW the difference in acceleration and response is nice.
 
#19 ·
It def. looks like the pinion seal (input seal, whatever you want to call it). I replaced this on my M3 about 4-5 months ago, the seal its self was like 43 dollars. It took me about 6-7 hours to do the job and that was with a lift. If you are not mechanically inclined at all, or are only just beginning to do D.I.Y. work do not attempt to do this as you will have to drop sections 1 &2 of the exhaust, the heat shields and the driveshaft and if you dont tighten the big 36mm bolt in the diff that goes on top of the seal (I can't remember for the life of me what it is called) just right it will f everything up in there. Otherwise, take it to a good indy shop and have them do it. Option 2 is pretty simple, just leave it be and get under there like once a month and top off the fluid in the diff as long as it stays a nice slow leak (not leaving anything on the ground).