02 4.6is transmission issue?
 

Hi, so my 02 x5 4.6is has randomly had a problem where it will automatically downshift on the highway at certain speeds even when the road is completely flat. It then proceeds to do this 2-3 more times uncontrollably before it stops. It even does it when I put it in sport mode and manually try to put it back in 5th.

thanks!!

how many miles?does it do it downhill and uphill too?any squeal of any kind?do you do any towing? you might not have enough oil in that transmission.My E39 540i with 59k miles used to do this; coming to a stop, before the car stopped completely, it felt like someone rear ended me..came to find out the oil was low...well, a good 3 quarts low:yikes:...
I think it might be time for a tranny refresh on yours...(oil/filter)

It has about 139k miles on it. I did a drain and fill around 120k. When I floor it there is a very high pitched squeal in between gears at high rpm.

When you changed the oil, did you move the shifter for a few seconds in each gear to allow oil to flow thru all passages?
Did you refill at the correct temperature?
Check again, your level is low .

My indy changed it about a year ago. I'll have to ask how he did the change.

Agree that it’s certainly worth checking the fluid level (engine must be ticking over while the level is set). In addition, the transmission controller has a ‘cooling strategy’ mode which monitors the fluid temperature and if it exceeds a threshold value, downshifts the transmission and inhibits upshifts to keep the oil pump speed (& therefore fluid flow through the cooler) at maximum. Usually restricted coolant flow through the main radiator or the oil cooler are the culprits (they get bunged up with age), although occasionally it can be caused by a faulty fluid temperature sensor in the transmission wiring harness.

Phil

ATF oil need to be at a certain temp when you are checking the fluid level. If the Indy doesn't know that much about the trans he could have filled it when the trans was still hot. ATF expands with heat so if the ATF was hot he would have put less ATF into the trans since the ATF in the Torque Converter would be in the expanded state.

Whenever I change ATF I would drain it the night before and let it sit over night. I will refill it the next day while monitoring the ATF temp in the trans.

Unless your problem started right after the fluid change or your transmission is leaking fluid I would not expect the issue to be low fluid.

It may be as simple as having the transmission software re-installed. I would take it to a well recommended Indy transmission shop that does lots of work on BMW transmissions and have it diagnosed.

It has done it for some time now (about a year) but just randomly.

Did it start before or after the fluid change and if after how many miles after?