Fixed my 2006 750Li transmission for $500, it was a broken bridge seal, see inside

[AuntJemima]

This is a repost of my reply to 377Z in my earlier transmission post, this post has info on my transmission repair experience which others here may find useful.


"377Z, YOU ARE THE BEST, it was a broken bridge seal. My indy fixed my transmission for $500 total 2 week ago. He said "lets drop the pan and see if the bridge seal is broken". The bridge seal was broken. He replaced it and 2 other gaskets, drained 8 quarts of my 12 year old fluid, replaced with new BMW trans fluid, and it works great at this time. Parts were $250 (mostly cost for BMW OEM fluid), he only charged me $250 for labor.

I did some research online before we pulled the transmission pan, some people said it is usually the valve body and you can get it rebuilt. I found a valve body rebuild service on Ebay for about $650, their phone is 1-888-511-7369 or 513-886-1215 in Cincinnati Ohio. I phoned Matt at the rebuild service and he said if I couldn't shift out of park it was probably a broken bridge seal, not a valve body issue. I could see why Matt didn't flourish in corporate America when he worked as the company IT guy, he is too honest. He has some interesting stories of his time in corporate IT.

Long story short, if I had taken my BMW to a dealer, I am afraid they might have sold me a new transmission for 12 billion dollars as BMW dealers seem to avoid any service of their transmissions. I have to question why an $85,000 car would have a plastic transmission bridge seal prone to breakage? Apparently some after market supplier makes a bridge seal replacement out of metal, why cant the OEM?

The 12 year old trans fluid with 53K miles looked like used motor oil, black. It didn't have odor other than smelling like transmission fluid. Time will tell if I damaged the transmission driving it until it displayed a "transmission overheated" message and shut down. I was going to drain and change the 12 year old transmission fluid anyway, so this repair didn't really cost much more.

You really need an honest independent repair shop if you are going to have your older BMW worked on by others, that and you need to do your own research..."

[zener]

Mine had 202k miles and bridge seal was still in good shape. But I replaced all the seals while I replaced the solenoids.

So it's not bad for a plastic seal.

[AuntJemima]

Mine had 202k miles and bridge seal was still in good shape. But I replaced all the seals while I replaced the solenoids.

So it's not bad for a plastic seal.

Zener Diode, glad you got a good one (bridge seal). Maybe the transmissions run cooler in Finland weather and plastic parts are less prone to stress and breakage. The bridge seal failure is not uncommon on our e65 in the USA from the 5 or 6 people I talked to at the parts suppliers and rebuilders. Our temperatures are over 90F much of the summer and the temps on blacktop roads are often higher.

[377Z]

I had a '82 Cadillac HT4100 with 137K on it before it blew a head gasket, that doesn't mean it wasn't common to see failures at much lower mileage (because it was common). Point is there will always be someone who gets atypical life out of something, but these boards are LITTERED with people with broken bridge seals, its a common failure point.

Just to cross info from other threads in the hopes of helping someone else, these transmissions are not rocket science. The mechatronic sleeve is a pain in the rear to reinstall but if you have a sudden trans problem a DIY fix is not beyond someone mechanically inclined with a clean area to work. I did a valvebody rebuild on my '06, it had a bad solenoid but I did it as a 'while you're in there' thing. I actually brought mine home on a trailer and had to do it to get the car to drive under its own power, has now 6K+ miles on it since and driving well.
Here's another thread. I didn't do a full scale repair thread on it, but the zip kit comes with good instructions and there are some helpful 6HP videos on youtube.

https://www.bimmerforums.com/forum/s...highlight=377z

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Funny, I didn't notice he is from Finland, you are probably right. When I had the E38 it was known that US models had hotter thermostats, not sure but suspect that's the case with E65/66 too. Evidently the timing chain guide failures are unique to the US--that may be the case for these trans seals as well. I think the temp thing is for emissions, fuel economy, or both. Not worth it IMO, I'd rather have a car that lives longer.

I actually bought a cooler thermostat for my '06 off ebay, though I understand you can do a DIY mod as well to the factory one.

[zener]

Yea, I read bridge seal problems too. And when i bought the car last winter it had broken thermostat and when I replaced it was original from 2004 and my car is 2004. Coolant temperature never got over 140F before I replaced the main thermostat.

So god knows how long the thermostat has been bad and engine running low temperatures. And I guess now my transmission heat exchanger is bad, since coolant temperature doesn't wanna go much over 176F anymore. Last winter it was closer to 198F... Diesels have 88c thermostat.

[SHAS]

Today I have changed the Transmission fluid to my 2006 BMW 750LI, mechatronic adapter and sleeves. I have used "
Valvoline MaxLife Multi-Vehicle Automatic Transmission Synthetic Fluid" and it's works like a charm.

[TxGR8White]

There are a couple of places where you can get the bridge seal made from CNC’d aluminum - it will NEVER break again. Cost is about $45-$50, but well worth it.