1991 535i auto trans downshifting hard

[Robert K]

I have a 1991 535i with approx. 137,000 miles on it. It's always been well maintained, including changing the trans fluid and filter every 30,000 miles. Every so often, the trans downshifts hard when coming to a stop. But then, not an hour later, it will downshift perfectly. Since it will work perfectly most of the time, I figure it's not a terrible problem. I'm figuring it's probably electronic since it seems to be intermittent. Does anyone out there have any ideas where to look or what to check? It's one of the only real problems the car has. I'd like to get it figured out and fixed. Any help would be appreciated.

Grace and peace,

Robert K
1991 535i

[Kalevera]

I would be changing the fluid and filter on the 4hp22 every 15k miles. How does it do on the 3/4 shift? Mine has a similar issue that I attribute to a faulty trans computer: it pendulum shifts between 3 and 4 during some slow accelerations (around town driving) when warm. Sometimes the 3/4 shift is abrupt (again, when warm..it's somewhat normal for it to be abrupt when cold), but seeing as it's a ZF reman with less than 1500 miles on it, we're suspecting the computer.

best, whit

[spoolinturbo]

how hard of a downshift? jolting? because its intermittent does not rule out a mech. error i would say. i've pulled trannies but am by no means a tranny expert. Check with a local transmission company, there is a place by me that can hook it up to every wire known to man and tell you whats wrong with it...cost like $65 for me...

[pundit]

I have a 1991 535i with approx. 137,000 miles on it. It's always been well maintained, including changing the trans fluid and filter every 30,000 miles. Every so often, the trans downshifts hard when coming to a stop. But then, not an hour later, it will downshift perfectly. Since it will work perfectly most of the time, I figure it's not a terrible problem. I'm figuring it's probably electronic since it seems to be intermittent. Does anyone out there have any ideas where to look or what to check? It's one of the only real problems the car has. I'd like to get it figured out and fixed. Any help would be appreciated.

Grace and peace,

Robert K
1991 535i
Hi Robert,

Mine ('90 535iA) has the exact same symptoms. It occasionally has harsh upshifts (not consistant either) but it's the downshifts that are the main problem. Sometimes the final downshift seems to hang on to the last few KMH's and when the car has almost come to a stop, it suddenly downshifts letting go with a thump through the driveline. I can feel it almost fighting against the brakes. Mine has 173,000kms (110,000 miles) and has been regularly serviced. I did a trans service only about 5,000km's ago but the symptoms are still the same... erratic. If you come up with a fix let me know and I'll buy you beer!! :D

Here's my last post on the subject... Harsh Shifting (http://www.bimmer.info/forum/showthread.php?t=9658)

[Kalevera]

Guys....

That's the same thing mine does...only it has (on two occasions) practically stalled out the car.

Once again, have to suspect the tranny computer....won't know for sure unti next week.

best, whit

[Tiger]

I suggest you change your fluid to something else... not all tranny fluid are created equal... I know for a fact that Valvoline ATF Dextron is far better than Mobil ATF Dextron... regular fluid...

Perhaps you might go with Pennzoil MultiVehicle ATF,,, semi-synthetic or Redline D4ATF for full synthetic and similar.

It is important to flush out as much as of old ATF fluid... not just drain one time... but three times with a week worth of driving in between... I suspect one of the valve is sticking...

[632 Regal]

royal purple has a dextron III that is supposed to be 100% synthetic as an option for you. It's pretty cheap too.