[E36Racer]

So I tried a search and couldn't really find anything that seemed to fit the bill. Here is my issue, my wife's 2010 328xi has an odd bucking/trans slipping under acceleration around 25-30 when you slow for a turn and then roll back on the gas. It's an auto so I cant tell if it's the trans or something with the transfer case. This is the first auto BMW I've ever owned, also the first x-drive as well.

It does it in both regular and sport mode under normal throttle application. I haven't tried to replicate the issue under full throttle because I figure that might just cause more damage. It has 60k miles, and all of the fluids in the entire car were changed at 52k, and they all looked great (literally every single fluid in the car, including greasing the muffler bearings...). No lights are on, on the dash, which I'm really shocked about since it is not a "once in a blue moon" issue. I can replicate the problem at will.

Any ideas?

If the trans or transfer case are about to shit the bed, it's getting traded in next week on the AMG she wants. Which 1) I don't want to pay for and 2) don't want to taint my driveway with either because neither of my cars are giving up a garage spot.

[niquehawk5]

Sounds alot like the transfer case motor/worm gear. Do a couple searches for that and see if some of the discussion there fits your issue.

[E36Racer]

Well the issue finally progressed and threw a CEL (misfire cyl 5) which went away with a restart. Cleared the code to see what would come back and about a week later it started idling rough and CEL was always on. Replaced the coil pack on Cyl 5 and all is good in the world. I also changed the plugs while I was there but before swapping the plugs I just put the coil in to make sure that was in fact the issue and not the plug.

After reading up about the worm gear issues I thought that was going to be the problem based on the descriptions, because at first it really did feel like the trans slipping more so than dropping a cylinder. I was surprised that the coil intermittently worked for that long before finally dying. Trying to convince the wife the car won't leave her on the shoulder and to wait until the CEL came on steady before I do anything was not easy but glad I did before digging into the transfer case.

[niquehawk5]

Nice, glad to hear you got it sorted out. Relatively simple fix compared to the alterantives

[only1harry]

Good to hear you fixed it. My 335 xDrive does something similar lately - when I am in mid-turn. I hit the gas and the car does not accelerate like it used to, but waits until the car is almost past the turn and straight and then I get a surge of power. It does nothing when I get on the gas mid-turn. What could that be? I do have more body roll than usual lately so I am trying to sort that out, but it could be it doesn't give me power due to loss of traction?

[E36Racer]

only1 - If your car is falling on it's face when you are mid-turn I could see how that would lend to the impression there is more body roll. Or you might have beat sway bar end links, hard to say. However, if there is a mechanical issue causing excess body roll, it's easy to figure out by figuring out what has a ton of slop in it.

In regards to your issue being the same, I guess it could be but you also have a turbo. Since turbo lag adds a layer of complexity to the diagnosis I'll tell you the same thing I told my wife. Try to get it to act up until it's pissed off enough to turn the CEL on and then pull the code. Since in these situations the computer can get confused with mixed signals, clear the code and wait for it to come on again. If you get the same code the second time, then take it from there. If you get a different code, see how they might be related and post your results on the forum if you can't figure it out.

[only1harry]

Thanks. My car has 35,600 mi. on it so I am not sure if it could be anything "mechanical". I hope not anyway, but you never know. I did replace both front and rear end links 2 weeks ago but it didn't make a difference. It could be the rear sway bar bushings, but 2 shops I went to said they look fine. However I can move the rear sway bar a little back & forth (front to rear, not sideways) when I grab the end links or the sway bar with my hand and give it a good tug. Is there supposed to be any movement at all in the sway bar? I think the problem could be subframe bushings because I hit a couple of big pot holes and that's when the handling, bounciness, and instability (floatiness in the rear, etc.) started coming on gradually, until it got bad and the body roll became more evident. It took 7-8 months to get to the point where I started hating the car. Before the potholes (both sides) the car was perfect. So in the process of trying to get the car back to normal I have installed Bilstein HD shocks (on stock springs) with all new shock bushings, front lower control arms, and end links all around, but not much has changed, and I feel the issue in the rear somewhere. That's why I think it's not mechanical or in the diff. or transfer case. It feels like the rear sway bar is not doing its job 100%, but there control arms and other other arms back there that could be having an issue - but I am told the rear bushings "look fine". So I suspect subframe bushings that all those other arms attach to. It's hard to tell though without spending a ton of $ replacing stuff

Harry

[E36Racer]

Well that is interesting. Potholes suck. Typically, with a car on a lift or sitting on the ground, you should not be able to get much movement (if any) in the sway bar by just grabbing it by hand. And I would thin that front to rear movement in the sway bar should never happen. Can you identify where the movement is coming from? Id the bar moving in the bushings or are the bushings moving in the mounts? I know with E36's, it was not uncommon for the rear sway bar mounts to fatigue and sometime break off the subframe. I think it would be odd a bushing would be worn at such low mileage. Get underneath the rear with a pry bar and check every piece of the rear suspension (and the subframe) to see what has movement and where it is loose, then go from there. I'm not as intimately familiar with the rear suspension on the E9X as I am with the E30, E36 and E46, so it could possibly be a rear ball joint or something. But the first step is figuring out what has play in it and where, then go from there.

The other thing to consider is maybe the pot holes knocked the rear alignment out of whack. Even if the car still drives straight the rear alignment could be off. See if the tires have any unusual wear characteristic.

[only1harry]

Thanks for the advice. I definitely need to get under the car but have to take to someone to put it on a lift and they don't allow me in the shop. The ones I took it too said "nothing jumps out at them". If you ask me they did not check good enough and they certainly did not use a pry bar.

I have done many alignments since but the car never really goes straight.

[E36Racer]

Put it on jack stands to shake it down if you have to. If you've had a 4 wheel alignment done and it crabs down the road, something is most likely bent causing one of the wheels to be either too far forward or back. Even 1/4" will cause havoc.

[only1harry]

I did notice a difference in caster in the front, which means something must be bent. I am thinking of taking it to a frame & axle shop here in town to see if they can take some measurements and figure out why the caster is different by almost 1/2 degree from the left to right.
Also I noticed after I replaced the stock shocks a few weeks ago with Bilsteins that the wheel well gap is different in all 4 corners after the shocks have now settled. Something is definitely not right. I believe the passenger rear corner is lower, thus pulling up the opposite diagonal (driver) corner up front making it have a greater wheel well gap than the passenger front. Or the other way around. The front driver side that has the biggest gap (is higher) pushes down on the opposite corner - the rear right. The difference in caster could have done this. Probably when I hit the pothole.

Is it possible the strut tower got bent or slightly deformed upon impact? Is it easy to tell without removing the struts?

Thanks,
Harry

[only1harry]

duplicate post, sorry

[E36Racer]

Sounds like you really need to get the car measured by a body shop. I don't know if you would be able to see by eye if a strut tower was a little off. And my guess is that if the top of the strut is off by even a couple mm could potentially have a noticeable impact on the car's characteristics