Deceleration Slack

[Renman]

I'm a FNG to this informative site. I have a '94 530i V8 automatic w/ 124k. Just developed an issue whereas during deceleration (45+ mph) I can feel a pronounced "slack" in the drive. Transmission appears to shift OK, no trans program alert and does not appear to occur during acceleration. The "slack" is only momentary but definitely have a problem here. Took the car into lcoal BMW specialist (non-dealer) and after inspecting the driveline he referred me to a transmission shop. Has anyone experienced this "slack" symptom that can advise me. Thx! -Renman.

[632 Regal]

You might have some sloppy engine/trans mounts, inspect your guibo and the rear end mounts. If you arent having trans issues or check engine codes its more likely a mechanical deal going on. Also check the center bearing for shits and giggles even though you havent complained about any clunking, might be excessive play in there also.

Good luck!

[Renman]

Thanks man. I don't want to be a complete neophyte tomorrow when I meet with the transmission guy. I like what I can see of your 530! Mine's same color. Sure cleans up nice. Gotta get this fixed.

[Renman]

Hey chief, I have just finished with the tranny guy and he tells me it appears the tranny is OK, however thinks I need to install a "EPROM CHIP" (dealer item). Can you shed some of your expertise on this subject. He claims that it "might" tighten up that slack that I described. Thanks for any help here.

You might have some sloppy engine/trans mounts, inspect your guibo and the rear end mounts. If you arent having trans issues or check engine codes its more likely a mechanical deal going on. Also check the center bearing for shits and giggles even though you havent complained about any clunking, might be excessive play in there also.

Good luck!

[632 Regal]

Did he check for slop in the rear differential, the cv joints, the drive shaft and all the rubber mounts for the engine/trans/rear differential and the guibo?

Havent heard about a magic chip yet.

[Robin-535im]

There are a half a dozen bushings in the force path from the wheels to the chassis, many of which can wear out. When they do, you can get slack in the drivetrain and sudden on or off of the gas pedal will make the car "kangaroo", as someone said before. Our cars are right in that "original rubber parts are wearing out every day" stage.

The bad news is, I don't know of a good way to find only the bad ones and replace them.

The good news is, you can probably get every bushing on your car for $500 total, and install them yourself with a few well-timed tool rentals.

Engine mount, tranny mount, diff mounts and guibo can all contribute to slack, as can the rear suspension: subframe bushings, trailing arm bushings, upper shock mounts. All of these except the subframe and trailing arm bushings can be replaced with common tools, these two need bearing press fixtures (or superhero thumbs) to replace.

So back to the bad news... someone smarter than I will have to tell you how to check them - the other option (not a bad one either) is to replace them all.

HTH

[cjones]

In my M5 I had a clunk when pressing the accelerator and another one when suddenly releasing it. The mechanic replaced the subframe bushings and that solved the problem.

[Renman]

Good info Gents. Thank you. For what it's worth, I'm putting an updated factory EPROM in the transmission module tomorrow. I doubt that this will resolve the "slack" but I'm a sucker for anything that might ensure the tranny stays healthy. By updated I mean that this EPROM is supposed to be designed for trannys that are broke-in. Ever heard of such a thing? Hopefully I will report some positive result? Cheers! (no saggy diapers here, no matter how far the mechanic reaches into my pocket) -Renman

[liquidtiger720]

what do you guys mean by slack? i can feel, that if i let off the pedal, and coast, i will feel as if the transmisison will disengage, and if i add a little throttle, it feels like it will engage again....sorry guys, just wondering if that was a problem, because i just got my car back from a rebuild.

[Renman]

My definition of "slack" symptom I'm trying to correct: when the car is at cruising speed and I let off on the gas, it's not smooth (actually feels for a split second that the weight of the car is pounding forward on the frame). I've had "some" of the obvious checked out, e.g. driveline/ujoints/tranny and engine mounts to no avail. Right now having the updated eprom installed which my tranny expert tells me might help this issue. I'm not real confident as I believe the above advise that it's in a joint, bushing etc somewhere on my frame. Good luck and I get the car back Thurs regarding that eprom which may be of interest. My next stop is probably the best frame/suspension shop in Pacific NW (so in the doghouse). -Renman.

[tim]

FWIW,

The eeprom update had to do with the shift pattern as many early owners complained of excessive shifting on hills, and a bump downshift while going down them. The dealers usually did this service, and you can identify whether it's been done by an orange circular sticker placed on the case of the tranny control unit.

[Renman]

OK fella's, here's an update on the eprom install. It did help tighten up the transmission. But the "slack" problem continues (I sorta thought it would). Turns out to be the tranny and even though I could drive it this way for at least a bit, I'm bitin the big one and having an overhaul. I could get the tranny fixed cheaper with a part or two (no metal shavings in the pan), however I'm diving in all the way (I'll be in the dog house for sometime for sure). I'm using a shop that most if not all of the Portland OR area bimmer indy's use, Automatic Transmission Service. The problem is that when the car is cruising and you begin to let off on the gas, the tranny is supposed to immediately go into a sorta "coast" mode so smoothly that we don't feel anything. Unfortunately, mine will not do that, hence the ugly "slack" phenomenon occurs. What guys like me won't do or spend on these cars (I have 3 of em). Smart guys, like many of you might fix it yourself!! Tranny's? Not sure.

[632 Regal]

keep us updated!

[Renman]

Yeah, probably a $20.00 part. I never promoted myself as being very bright (just broke). My tranny parts are sitting on a work bench as we speak. Gotta keep smilin though.