Transmission - BMW Forum

Bunny Capricorn · 03-16-2005, 10:07 AM

1992 BMW 525i: Just got a new Automatic Transmission put in. The problem is the down shift from 2 to 1......extremly harsh for about 3 weeks now. Is there a solution to this problem?

bgwoody · 03-16-2005, 09:05 PM

My 89 535 would shift hard 2 down to 1 once in a while Was it shifting harsh before the rebuild? If so maybe electronics. Did you take it back to the shop?

Bunny Capricorn · 03-17-2005, 01:46 PM

It was not doing it on my old Tranny, but I know for a fact that my mechanic didnt disconect the battery. I keep hearing that the computer may need to be reset

. I will try this and let you know. If anyone else hears anything please let me know.

Thanks!!

bryan1970 · 03-17-2005, 08:38 PM

unless the Transmission control module need to be replaced or reprogrammed you could try a battery reset. basically just take both the cables off the battery for about a minute. and what you can do to help the car discharge is touch the two cables together. OF COURSE THAT IS WITH BOTH THE CABLES DISCONNECTED FROM THE BATTERY!!!!!. by touching them together it will discharge all the capacitors that may store some energy in them.

Bunny Capricorn · 03-18-2005, 06:34 AM

I will try that, but I noticed when I drove the car in S3, the hard down-shift was gone. Totaly non-existant(totaly).....What do you think that means?

bryan1970 · 03-18-2005, 07:20 AM

hmmm it almost sounds like the control unit is starting to go bad? don't hold me to any of that but thats just what it kinda sounds like to me. i'd take it either back to the place you had the transmission installed or to the dealer so they could give a better diagnosis.

Bunny Capricorn · 03-18-2005, 08:02 AM

Do you know were the TCU us located on the vehicle? (1992 525i)

Bunny Capricorn · 03-21-2005, 08:13 AM

Ok folks.......here the results of disconecting the battery. I did the disconection, left it off for about 15min. I drove the car yesterday and the process seemed to help the Hard Down Shift (2-1). It hasnt stopped totally, but out of stopping about 30 times, I felt the hard shift about once or twice. So I would like to thank you guys for your suggestions.

bryan1970 · 03-21-2005, 10:07 AM

yeah if the battery reset seemd to do really anything i would lean towards some sort of control module failure. i'd get it fixed before it trashes your tranny.

///M Power · 03-21-2005, 01:05 PM

A hard sequential downshift? That is how it should be...so just rev match.

Bunny Capricorn · 03-21-2005, 01:08 PM

Like I said....since I reset the car....it's been driving better......not the hard down shift as much(ratio of 2/30 times it will do it; guestamation).....like the TCU is trying to get used to the new Tranny or something

BUT...If in the event that I do need a new TCU(Transmission Control Unit); does anyone know were my best options are to get it?

Thanks!

bryan1970 · 03-21-2005, 06:24 PM

the dealer would be a good place. although they would probablly have to order it for you.

Torque · 03-21-2005, 09:53 PM

When exactly does it downshift hard ? When you step on it all the way from cruising at 25 ? Or when slowing down gently you hear it 'thump' ?

Bunny Capricorn · 03-22-2005, 11:21 AM

Well..........Before I diconected the battery it was doing it at a fast drop in speed or low drop. But since the disconection.....its not doing it at a slow drop of speed. The only time it's doing it is when Im coming to a quick stop now. Got so intuned to it, not sure if thats normal or not.....

Torque · 03-22-2005, 04:40 PM

Quote:

Originally posted by Bunny Capricorn@Mar 22 2005, 01:21 PM
Well..........Before I diconected the battery it was doing it at a fast drop in speed or low drop. But since the disconection.....its not doing it at a slow drop of speed. The only time it's doing it is when Im coming to a quick stop now. Got so intuned to it, not sure if thats normal or not.....

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Hm... my tranny will downshift to 1st a little harder than normal during the slow stops... when i stop quickly i cant feel or hear it at all.