transmission - a mind of its own!!

HSV2006 · #1 09-10-2009, 11:21 AM

Folks, what searching I did of the archives did not reveal a problem like this. If it's been previously covered, I apologize - but it was not there to easily find.

Here's the issue. My '02 X5 4.4 transmission has a mind of its own.
You can be cruising at 55 MPH, and it decides it wants to be in 4th, or even 3rd! That's one example of this odd behavior.

In city driving, say at 45 MPH, I can let off the accelerator to slow down for a traffic signal. The transmission will downshift, slowing the vehicle down through each gear, to 2nd gear.

These "actions" are quite random. I've no clue. A possessed unit?? LOL!

SO... any ideas? What's the scoop?

Oh. I did try the "transmission reset" - to no avail.

Thanks!

Kim

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serg10 · #2 09-10-2009, 02:56 PM

I have a similar issue with my 04, 4.8 X5. In my case, it seems to happen when I come to a somewhat quick stop, say at a light or stop sign. When go to take off, the car revs fast and almost to the 4 on the RPMs. I've taken it in several times and they swear it's fine. The dealer told me these cars have "tricky transmissions". One guy told me that I just need to give the car more time to downshift as I come to a stop. I'm not slamming the breaks or anything, so I don't see why the car can't downshift at different speeds.

GershX5 · #3 09-10-2009, 04:14 PM

Are you guys in Sport Mode when this occurs?

TheKingSim0n · #4 09-10-2009, 04:49 PM

This is a common problem with the X5, I own an 01 X5 and I recently just hit 117,609K.

The down shifting became such an annoying problem to the point that I try not to stop the car as much while i drive, i tap on the brakes every now and then just so i don't feel it as much.

Im very grateful I have 3rd party warranty on my X. I will be rebuilding my transmission i figure around January, dont ask me why I am waiting.... Its for a few reasons...

I noticed alot of X5s past 100K have a hard down shift from the transmission, I also have had a few friends who rebuilt there transmissions and it was gone and everything is fine with there trannys now. I know someone with over 218K now and hes running strong after a rebuilt transmission. He of course had to maintain it properly by changing Spark plugs on time, replacing brakes and rotors on time, do your oil changes on time, not KILL the car by driving constantly on 7 RPMS....

From my personal experience, as long as the engine has been taken care of, they can last a life time....

serg10 · #5 09-10-2009, 05:01 PM

I only have 52K miles on mine and I have CPO warranty until 7/10 but can't get a dealer to acknowledge a problem with my trans. I'm not in sport mode when this happens. I love the car but this issue can get a little annoying, especially when it jerks you into the next gear after take off. I live in Chicago so it's hard to avoid quick stops sometimes!

cmartin248 · #6 10-19-2009, 07:45 PM

I also have a 2002 that tends to shift at random around 50-60 mph,, it will go down to 4 or 3 like it is trying to kick down to passing gear but only during very light acceleration. I also have the down shift problem. It really doesn't appear to be in the transmission, because it doesn't slip or not shift correctly. I had the exact same problem on a Jeep and it was the Throttle position sensor making the computer think the throttle was at a different location and shifting the trans according. The X5 doesn't have this sensor but rather an ECU which is very expensive. It appears to be electornic and not mechanical, hence the reason many people rebuild the trans and it still does the same thing. Maybe a good BMW trans man could shed some light...

HSV2006 · #7 10-20-2009, 04:47 PM

Since beginning this thread, here's what I've done.
To answer a question, No - not in the sport mode at all. Just in normal Drive. Random shifts as some of you have observed. Now for what I've done.

My independent garage said my transmission showed a temperature sensor fault. I replaced the following items: the wiring harness with temperature sensor (that's the description); the 3 servos; and, the rear pulse generator. When I removed the pulse generator, the oil around it was very dirty - worse than the regular oil. Beware of the torx bolts. I had 2 to strip on me during all of this. I also pulled the front pulse generator and noticed the same bad oil. I cleaned that pulse generator.

Put everything together and added fresh fluid (I changed the previous fluid at 70k miles).

The result? ALL is well!!!!! In the combination of what I changed, it fixed it. I thought about the link over to the throttle position, but this "fix" shot down that notion.

TheKingSim0n · #8 10-20-2009, 06:17 PM

Quote:

Originally Posted by HSV2006

Since beginning this thread, here's what I've done.
To answer a question, No - not in the sport mode at all. Just in normal Drive. Random shifts as some of you have observed. Now for what I've done.

My independent garage said my transmission showed a temperature sensor fault. I replaced the following items: the wiring harness with temperature sensor (that's the description); the 3 servos; and, the rear pulse generator. When I removed the pulse generator, the oil around it was very dirty - worse than the regular oil. Beware of the torx bolts. I had 2 to strip on me during all of this. I also pulled the front pulse generator and noticed the same bad oil. I cleaned that pulse generator.

Put everything together and added fresh fluid (I changed the previous fluid at 70k miles).

The result? ALL is well!!!!! In the combination of what I changed, it fixed it. I thought about the link over to the throttle position, but this "fix" shot down that notion.

Well I am hoping that when i rebuild my tranny there going to do all that for me.

cmartin248 · #9 10-20-2009, 06:25 PM

Hey thanks HSV2006,, you may have found a common failure in that "wiring harness temperature sensor". It seems mine is sometimes a little temperature related. Where did you find the harness and sensor, how much? As for the servo's and pulse generator. They don't really fit my diagnostics, but I will clean them and test them. Is the harness inside the transmission pan? Any help would be great....

lay3r3 · #10 10-20-2009, 06:39 PM

I had a similar problem and the stealer ended up replacing a wiring harness that was inside the tranny oil pan. Apparently the housing for the harness had failed so oil was getting into the wires. I couldn't reproduce it so had trouble getting it fixed. Eventually it finally got to the point that it was permanently screwed up so they were able to find it. Bizarre but has been solid ever sense so like 5 months.

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