E70 X5 Water in Rear Differential
 

Hi guys, I'm new round here, but wanted to solicit some opinions on my situation.

I use the X5d to haul around a boat for short distances of less than 15mi each way to the lake. To launch, I have to back the car in the water until the exhaust is barely burbling on the water or where the water line is just about at the bmw symbol on the rear wheels.

The problem: I noticed a few drips of diff fluid on my garage floor and when I opened the plug nasty cream colored fluid came out. Lots of it. Theory goes, it filled with water and when heated, it was pushing the seals out causing the drip.

Question: How is water getting in? I haven't been able to find a vent or breather valve anywhere on the diff. Is the temp difference of a hot diff hitting cold water sucking water past the seals? How can I prevent this going forward other than changing the fluid constantly or trying not to back in to far on the boat launch?

Thoughts?

I'm also new to X5/E70. FWIW, the rear diff looks quite similar to my E90 335D one. It is specifically a 215 size (bigger than normal for a sedan). I come to my point. I had a LSD installed into it and noted the internal features. Up higher on the diff cover, I see a very small vent hole in the cover. I will snap a picture and post.

I am no means an expert, but I think the breather is on top of the differential cover. See next to the number "1" on the real oem image.
https://www.realoem.com/bmw/enUS/sho...diagId=33_1387

All differentials are vented, otherwise they would puke fluid when they got hot. When I used to 4wheel we would run a hose from the vent up high to prevent water getting in. I know E46 diffs have a vent (small hole) in the cover.

Crawled under last night with a mirror to look at the circular area on the top right side of the diff cover. Appears to be sealed. The vent on the diff still eludes me...

I've been using my X5 35D to launch my boat for the last 7 years, big question is why are you backing so deep into the water...

http://www.wardphotography.com/Boat/IMG_3546.jpg

All depends on your trailer setup..how long the tongue is, bunk height etc. When retrieving the boat I was taught to let the trailer come up to the boat and let the boat rest on the trailer opposed to leaving the trailer too shallow and motoring/sliding/ramming the boat into position which is rough on the trailer, hitch, boat, and bunks. Launching-boat should be fully floating.

As a boat owner I'm sure you've seen the shinanigans on the boat ramp.

For my trailer setup the rear tires are half wet to be in a good position for dealing with the boat. I could prob get away with not backing in quite as far, but would probably be in the same position with this diff. situation.

Now that I've had this problem I'll be more conscious about how far back I go, and perhaps will opt to be rougher on the trailer and boat to save my diff. Ideally I would like to find the breather vent and route as high as possible for a long term solution.


Btw, looks like the guy on the left side of the pic is in pretty deep too. Feet getting wet if he gets out of the car. Same situation...

He wasn't that deep in actually

http://www.wardphotography.com/Boat/IMG_3544.jpg

Heres a video showing just how far I get the X5 into the water. My wife was holding the aft line, and a random guy came to help pull bow line

https://youtu.be/qloBVqKP1CA

Great boat! Ya, we're in about the same situation. To get your boat off without the pushing and pulling you'd probably have water in your diff too. :). Thanks for the video! Hope someone knows where the breather vent is or Ill be yanking on my boat like that going forward.

vent in diff cover
 

Please see my attachment. The external side will have a small hole up toward the top of the cover. One qualifier. This diff cover is for an E60 (older 5 series). I would sure hope the vent hole in your's is way up on top as well. If you got water to center of your rear tire, depending on the angle of the boat ramp, your vent might still have been above water. Also, it would depend how fast you backed down the ramp too.

I would say change the fluid and hope for the best. I use a mighty vac ($60 at Oreilly Auto) to suck the old fluid out. It is intended to suck brake fluid through a caliper to bleed out the air. Best of luck.