525i auto trans interchange

[Rev Engineer]

Does anyone know the differences between the transmissions on the e34 525i? I know in 91 the e34 went to the A4S310 along with the m50 motor. Are there any differences between the years with the A4S310? The reason I ask is because the transmission in my 95 525i touring went out and I'm looking at junkyards for a used one. A nearby yard has a 93 525i and they're telling me that I can use its transmission if I swap the electronic trans module with it. They're willing to sell both for $500 - 125k miles. I thought that all A4S310 transmissions were the same. What could the difference be that requires a different module?

Aside from replacing it, does anyone have information on rebuilding these things!? I've got it pulled from the car and I'm tempted to open it up and find out what's wrong. The symptoms we're slight slipping in most gears, lots of slip while trying to shift into 4th, overall felt sluggish with terrible gas mileage, "trans program" eventually comes on, and smelled like burnt atf. The fluid looked and smelled pretty nasty when I drained it. I figured that a trans fluid change would not be enough to bring it back.

Any help or advice would be greatly appreciated. Thanks in advance!

[BMWCCA1]

I have no idea where you live since your profile isn't very complete, but over here in the U.S. it's a GM THM transmission so nearly any AAMCO repair shop can take a stab at it. BMW North America also offers a Value Line exchange program on some of the more trouble-prone automatics, like the E28 ZF boxes. Don't know if your dealers have such a program for your old cars, too.

[gtopaul]

Most trans shops will charge over $1200 to rebuild that trans. It's really comforting to know that it's a later version of the same transmission that powered the infamous Chevette. I've actually got a A4S310 behind the S52 in my Touring. I bought it off Ebay for $600 and it was just rebuilt but never used. It came out of a 94 525iT and when I dropped it in with the engine swap into my 92 it got program lights when accelerating. I had to get the matching TCM for that to be fixed. There is a difference in the software versions and they have to match the transmission. You might be ok since you have a later 95. I'd just use the original TCM and see if it works ok with the new transmission. If it doesn't swap the matching one back in.

Paul

[winfred]

93-95 525 and 93-95 325 (you need to use the output flange from your tranny, it bolts right on) these units will drop right in with no computer changes

[Karl]

GM calls the transmission 4L60E, and it's good for a lot more torque than the m50 puts out. I'd look for a competent independent transmission specialist if I were in your shoes.

[Rev Engineer]

Thanks for the information! That's good to know that the 325 and 525 can be interchanged. This helps the search.

$600 for a rebuild off ebay? That's very good! I've looked and looked and it does seem that the lowest cost rebuilds are in the $1000-$1200 range. For a used one at half that cost, I think I'm going to take my chances. Too bad rebuilds cost so much...

[Montreal525]

Thanks for the information! That's good to know that the 325 and 525 can be interchanged. This helps the search.

$600 for a rebuild off ebay? That's very good! I've looked and looked and it does seem that the lowest cost rebuilds are in the $1000-$1200 range. For a used one at half that cost, I think I'm going to take my chances. Too bad rebuilds cost so much...

Unless you are buying an already rebuilt transmission, don't buy a used one. If you plan to keep your car, have yours rebuilt, even at $1200.... I went that way and had to have the used one rebuilt after 4 months... Don't be cheap on the transmission, IT WILL come back to bite you on the ass later on if you are...

As far as years go, Bentley says there are some differences between 91-93 and 94-95 concerning gear ratios.

Jeff

[winfred]

the 91-92 tranny is different then the 93-95 not sure why they lumped the 93 with the 91-92, basically the non vanos cars and vanos cars have their own trannys



As far as years go, Bentley says there are some differences between 91-93 and 94-95 concerning gear ratios.

Jeff

[Rev Engineer]

Thanks again for the info! I went ahead with the gamble picked up the 93 525i auto transmission with 124k miles on it - $600 with 1 year warranty. With some amount difficultly, I managed to get the new/used one in this weekend. My first time changing out an auto on a bmw. I'd say manuals are a little easier and a lot less messy...

Before I put the trans in I replaced the filter, cleaned the pans, and replaced the front seal. I also flushed out the transmission lines with new fluid. The new/used transmission works great, except I get about a 1 second slip when it shifts from 2nd to 3rd. At low to moderate throttle, it either doesn't slip or it's not noticeable. At moderate to full throttle, the rpms rise 500-1000 rpms before 3rd kicks in. I've only tested full throttle twice in fear of making it worse – the only good thing is that 3rd does kick in instead of the rpms continuing to rise. The 1-2 shift is quick and positive at full-throttle. Haven’t found enough road to check that 3-4 full-throttle shift… All the gears and other shift points seem very nice and smooth.

Since I've got a 1-year warranty, I'll only be out my labor if I need to replace it. It's no small job and I'm not interested in doing it again any time soon so I think I'm going to drive it for awhile and just be easy on it for the 2-3 shifts. I could also try replacing the fluid a 2nd time - maybe try a different brand? I could also try adding a no-slip product and see what happens – any reason not to try this? Any other ideas? I don’t think my new/used trans is in any pending doom so I feel that I should be safe driving it for a few months. Maybe I can look into rebuilding my old transmission in the meantime.

So far no "trans program" messages have popped up with the new/used trans and I did not replace the module. Any chance swapping in the 93 module with help!? Maybe the trans computer just needs to be reset?

[winfred]

disconnecting the battery for a few seconds would wipe the tranny computer adaptations but it's probably ok, id double check that it's up on fluid, get it good and warm (5 mile or better drive) and while it's idling in neutral top it up till it's running out of the hole

[ricola]

has anyone ever tried to reman one of these at home? Any special tools needed? Is there a generic reman kit source we should know about? I can't imagine the clutches and lip seals and thrush bearing could cost more than a GM kit... What,, like $ 70.00 in parts..?

[Rev Engineer]

disconnecting the battery for a few seconds would wipe the tranny computer adaptations but it's probably ok, id double check that it's up on fluid, get it good and warm (5 mile or better drive) and while it's idling in neutral top it up till it's running out of the hole

Winfred,

I did top off the trans as you described. When I first filled it, I ended up a couple quarts short and then did what you described and I'm fairly confident that I've got it right. Temp was around 110-120F. I was actually surprised as to how much ATF the thing took - total of about 6-8 quarts. I lost track at some point...

I swapped in the '93 transmission module and the 2-3 slip actually went away! Wow. I'd be all happy, but apparently the '93 module is not compatible with ASC+T as the ASC+T light remains on and the button doesn't function. So, I left my '95 transmission module unpluged overnight and thought that the car might be cured this morning, but the 2-3 slip is still there. Maybe my module needs time to relearn shift points? Could the module have non-volatile memory? Another thought I have is to try to swaping eeproms between the modules - assuming they have removable eeprom chips.

Thanks again for the help! I'm fairly happy that the '93 module made the slip go away which leads be to believe that I will not have to pull the transmission again. Sigh..

[winfred]

they don't have a hard memory on the obd I cars, kill power to the computer and the memory is gone, not sure whats going on with the skip, can't say i've had one do that with one computer and not another, swapping chips may do something if they are compatable

[Rev Engineer]

I did a little more experimenting today with the transmission control modules. First I confirmed the symptom - approx 1 second slip between 2nd and 3rd gear. More throttle equals more slippage (higher rpms before 3rd engages), but 3rd always kicks in. Very repeatable in manual mode.

I found that the control module contains an eeprom - just like the dme. So, I swapped the 95 525i chip into the 93 module and plugged it into the car. The ASC light came on again so I didn't try going further. Next, I put the 93 525i chip into the 95 module. The ASC light turned off and the 2-3 slip went away. Very strange! Apparently the difference in software is making my transmission behave. Maybe touring software is different and the 2-3 slip is intentional!? I still need to confirm full ASC functionality before I consider this done, but it is certainly odd that the vintage of software has had such a big effect on slippage.