Bucking rear end? - United Bimmer Community

**doughboyea** · 06-06-2006, 11:02 PM

This has happened twice so far. Upon hard acceleration, I can feel the rear end "bucking." I'm not sure if that is an accurate description of how it feels... but it does resemble someone trying to learn stick and the car bucks, though this isn't as aggressive as that. It's subtle, the rear axel seems to buck until highway speeds. Could it be the Diff? I don't think it's the suspension....

Ideas? Is it something that could potentially be serious?

Dough

**celsdogg** · 06-06-2006, 11:46 PM

howcome you dont think its the suspension?

**xsperf** · 06-06-2006, 11:48 PM

guibo? what exactly do you mean by "bucking"

**Dudesky** · 06-07-2006, 06:01 AM

Feels like the wheels are "skipping"? This happens to mine as well sometimes. Under hard acceleration or just after hitting a bump/pothole, and particularly in a turn, the wheels have to struggle somewhat against the road surface to gain traction. It happens while the wheel is 'unloaded', and the intermittent grip as it tries to stick to the road can be felt as a slight forward/backward "bucking" motion. But it's not enough to screech the tires. I don't see it as a problem tho.

. . Or maybe it's just my crappy Kumho's

**EnvyM3** · 06-07-2006, 09:38 AM

The same thing happens to me but when you say "bucking".....Is it just one buck?
If i'm on the hwy and I let off the gas and coast, and then hit the throttle, it will give a slight buck and then accellerate. Is that the same thing you're experiencing Dough? If so I'm not worried about that as it used to happen on my 323 as well.

**doughboyea** · 06-07-2006, 09:43 PM

Thanks for the replies... let me try to explain it differently.

Again, this only recently happened in the 2 years+ I've owned her. I was getting off a ramp and merging. There were no potholes and the ground was not wet. I floored it to get into the lane. While my car does not have alot of HP, the front end did the usual slight rise, while that sensation of "bucking" occured. <--- that's not to say that the rising of the front end had anything to do with it, just to give you an understanding of full acceleration. So, instead of bucking, let's call it a by an audio description. It sounded like a "jut jut jut" that occured from the oneset of full pedal to release. It was a feeling of a series of slight hessitations that occured in a row.

Now, why do I say that I don't think it's comming from the suspension? Well, aside from my lack of knowledge in that area, I'd say it's because it doesn't feel or sound like it would be comming from that area. It felt centrally located.

Dough

**Chris** · 06-08-2006, 03:53 AM

independent rear suspension kickin in? it won't let yu just peel. maybe the conditions were right and it just happened. was it a lick or extremely smooth portion of road?

**Dudesky** · 06-08-2006, 06:35 AM

Well, maybe we could start with the basics . . . what's your mileage? Manual or auto? Now I'm thinking maybe some slight tranny slippage? Any leaks underneath, by the diff or the tranny?

**doughboyea** · 06-08-2006, 08:39 PM

Automatic, ~88k mi on the clock. Haven't noticed any leaks. Though I really haven't had a chance to look underneigth. Last dealer inspection was about 17 months ago. And chrisdoesntknow, smooth road.

Dough

**Dudesky** · 06-08-2006, 08:52 PM

I don't know, not familiar with E46's. With that mileage, maybe your trans may need an adjustment or a flush & refill; if I had to guess, it may be slipping?

**xsperf** · 06-08-2006, 09:17 PM

maybe its a misfire? have you changed your plugs / coils lately?

craig · 06-08-2006, 09:49 PM

mine does to same thing(but only from a stop/slow speed)

**c1apton** · 06-08-2006, 10:50 PM

Sounds like fuel or ignition hesitation from your 2nd description. With all the issues of gas these days, I'm a strong advocate of fuel line cleaners (Techron, STP gas treatment,etc) Once every couple months. Variables like brand differences, winter to summer blends, and normal seasonal temp changes - leaves alot of opportunity for moisture, condensation to get into fuels. Not just the moisture, but a "shellac" film that builds up in fuel lines also accumulates on injectors and can cause all kinds of weird symptoms. Even carbon build-up can cause hesitation - take a highway road trip (hour plus @ hwy speed, but just steady cruising) and see if that helps.

**doughboyea** · 06-08-2006, 10:54 PM

I used a cleaner about a month ago. I think it's mechanical.... meaning not related to the fuel system.

**xsperf** · 06-09-2006, 01:30 AM

so... have u replaced ur plugs or coils anytime recently?(sry just curious)

**doughboyea** · 06-09-2006, 10:25 AM

Well, I haven't, that's not to say that the previous owner didn't. Though the car was dealer maintained, I have a list of jobs done, all in code though.

So, the census is, it could be:
1. Normal
2. Slipping Tranny
3. Dirty Injectors
4. Bad Coils

Well, I don't think it's normal. If the tranny was slipping, wouldn't it be evident all the time? Just used an injector cleaner, but I really don't see how that would be the issue. Bad coils: Not sure on that one, but seeing how the coils are an integral part of the engine, wouldn't I experience the same at all times?

Dough

**Dudesky** · 06-09-2006, 10:47 AM

Quote:

Originally Posted by doughboyea

If the tranny was slipping, wouldn't it be evident all the time?

Not always. Some issues are gradual and progressive. Minor fixes if you catch them early. Like I said, it's just a hunch, and I'm basing this on past experiences with GM's . . I could be way off here. I had a Cutlass that would slip under heavy torque, and I let it go too long. Eventually, I lost the gears one by one, and it all started because I had a small leak I didn't attend to

**doughboyea** · 06-09-2006, 02:51 PM

Hmm ok, I'll keep that in mind. What should I look for if it was leaking? (Aside from drip marks on the ground)

Dough

**xsperf** · 06-09-2006, 04:47 PM

theres a tranny dipstick, theres a certain way to check it, you pull the parking brake up, and put the car in drive, i think, then check it

**doughboyea** · 06-10-2006, 02:51 AM

Quote:

Originally Posted by xsperf

theres a tranny dipstick, theres a certain way to check it, you pull the parking brake up, and put the car in drive, i think, then check it

Wouldnt' you know, the owner's manual mentions nothing of a dipstick for my car, nor can I find one in the engine bay. When I'm more awake, I'll look up info in my Bently Manual...

Dough