Replacing TCC solenoid, experience with GM5 transmission
 

I recently replaced my intermittently faulty TCC solenoid on my GM5L40E transmission (3.0I). This transmission has 121000 miles, never opened, never flushed, and I thought that it would be interesting to post here what I noticed while working on it.
I had the typical intermittent no reverse problem, not the one which occurs on ZF transmissions (broken reverse clutch drum), only the one caused by a faulty TCC solenoid. I picked up the information on the E46 forum (I posted the link here some times ago) and also in the Sonnax website: http://www.sonnax.com/tech-articles/TASC-TIP-02-09.pdf
In my case, I lost the reverse some times only when the engien was fully hot.

So I got a brand new TCC solenoid, pan gasket and bolts and a new filter from Pelican parts, then 5 liters of the original 8072B fluid to the local BMW dealer (they had no more than 5 liters and they sold it at 10 Euros (about 14 USD) the liter...).

After having drained the fluid and remove the pan, I was surprised to discover that the oil, although brown coloured, was not really dirty. the pan was perfectly clean except around the magnet. No metallic particles though, just a sort of light mud.

Removed the electrical connector to the TCC solenoid and first surprise, the connector clips broke in my hand without any force on them. Totally cooked by the heat and age.

Removed the clip holding the TCC solenoid and second surprise, the solenoid can't come out due to the transmission case!
So what to do without any good experience of dismantling such a transmission nor having a technical manual? After a deep look at the system, I finally decided to untighten the Torx screws holding the valve body (pictures below), just enough to drop the body a bit and get the solenoid out.

Third surprise, while watching to the solenoid in my hands, the plastic part (where the screen is located) broke. I know what you are thinking, that I'm a real brute, that I break all what I touch... Not at all ;), I didn't even put some force on it, once again it was cooked. Tried after to break the rest of the plastic part (by forcing on it this time) and all broke in small parts...

Refitting the new solenoid, tightening the valve body screws again, fitting the pan, new filter and gasket was no problem, and I refilled with fresh fluid (and a part of the old one as I didn't have enough new fluid) as described in this forum. I had to secure the solenoid connector (broken) with a small steel wire (seen on the last picture). Oh, and I flushed also the TCC solenoid and lock-up convertor bores with a sprayed new fluid due to notices in the Sonnax article (possibility of small particles in the circuit)... The tranny works very well, in fact just like before apart that I have the reverse ALL the time...

So, what to say about this already old (although working well) transmission?
Obviously it was surprinsingly not really dirty inside, no burnt smell, oil still in good condition apart the brown colour.
Obviously too, I was very surprised to notice that most of the internal plastic parts are really cooked? Just touching them a bit and they break... Something to do with heat and age of course but I think that (apart major problems to the gears, pumps or discs) it could be the main problem on these transmissions. Probably thet still work well along the years until one of these plastic fails completely and one of the connectors or one of the solenoid put some mess in the tranny.

Hope this will help.

Good information, thanks for posting this.

good job with posting the pics and the writeup. seems like an easy fix for the 3.0's out there

this is what mine is in the shop for right now. Not a reverse issue but a slow to build pressure to go forward issue.

Are you doing the same TCC solenoid replacement? Please post updates when completed. I'm starting to run into the same issue (slow to build pressure to go forward), but only when it's cold and/or the car have been sitting for more than a couple of days. Thanks.

Yeah. I thought that they were going to update the trans software based on the research I had done but the service manager said the solenoid was causing the pressure in the trans to be relieved over night. I get the X back on Monday so Tuesday morning will be the day of truth. We have been dealing with the issue for almost the entire time we have owned the X 2 years now. I will be glad once it is running right.

Thanks for the post. I am sure this is in my future some day.

Here are pictures of the solenoid, just after it broke in my hands. You can see the cracks on the 2nd picture, just waiting to break at any time...

adding this info to the party . complete rebuild info for the 3.0i transmission . file does not say fitted to X5 but essentially same transmission .

http://koti.mbnet.fi/pro-ht/Kuvat/au...ikko/5L40E.pdf

Hey All,
My 2001 x5 3.0i has been perfect for years. has 136,000 miles. sat outside in about 25 degrees for one day (first cold day of the year) and when i went to start it it was barely crawling at idle, then when I reved it it would barely move but RPM's would go up. I let it get up to normal operating temp and it was perfectly normal. Coincidentally, my guage cluster was completely unoperational as well. I drove home and put in the 45 degree garage and 4 hours later it was perfectly normal.
Im guessing this TCC solenoid is what is wrong with my X5, or at least I hope since it doesn't sound incredibly difficult to replace.
Your input with having some experience with this particular problem would be greatly appreciated.
One thing to note I changed the tranny fluid with Mobil 1 about 10,000 miles ago, no issues to start with, and no issues since then.