Squirly rear end - Subframe, Diff bolts, diff?

[spr]

My 09 just turned 50k miles. For some time now the rear end has felt pretty sloppy when putting down power. From a launch you can feel the right rear and left not having similar traction. At the shift if feels like the right rear is pushing back while left has no similar feeling if that makes sense. I think the right rear may be spinning more and left not from a bad limited slip. It has a very similar feeling to an open diff car. It doesn't feel like the two rears are connected like a proper limited slip equally putting down the power like my old p car did with LSD or old e46 m3 for that matter really.

I know many have said this is an indication of poss broken diff bolt but I have looked under and didn't find them broken and checked the torque on the diff and subframe and they seem fine. My thought is that the subframe bushings are toast as when putting the power down through corners it also seems to make the car wander a bit and I'm told if the sub frame is moving it will throw off the geometry toe and the like and make the car hunt around like that. It sort of reminds me of the wasted feeling of bad rear trailing arm bushes in my old e46 m3 but different.

Recently given this weird traction issue and how the car feels weird putting power down through really tight corners, I'm wondering if the differential's limited slip is toast. I've read all the articles but there is no real description of the three indicia of 1. Bad subframe/diff bushes, 2. Bad diff, 3. Broken Diff bolts.

Given the rain, the other day I was leaving a light with a painted crosswalk. I put the power down and I swear the right rear only started spinning and the traction control shut the car down which weirded me out. This makes me think the diff is bad as well as the right rear traction difference at shifts.

None of these issues presented until the car was doing some weird clunking back around 25k miles. At that time, I finally got all sorts of warning messages and took it in to the dealer where they diagnosed and replaced the rear speed sensor. I believe they have to take apart the rear end to pull an axle to replace same. If so, I'm wondering if they boogered the job since after then the traction from the left and right has never been the same. I swear it feels at times like an open diff. I'm wondering if the bastards swapped out my diff for a wasted one. It almost feels like that honestly.

Thoughts any help? It's really getting annoying. From what I've read it seems like at a minimum my subframe bushings are toast and possibly the diff bushes too. I guess I can upgrade to the solid subframe bushes and replace the diff bushes with stock as I don't want it too noisy back there.

The car is under an extended warranty, so I'm thinking I will bring it in and complain and see where that gets me. Suggestion on where to take it in SD? SD previously did the speed sensor work. FYI I will never take the car to Encinitas ever after they curbed both rims then blamed me for it when I picked the car up and the rims were sitting directly on the fucking curb. Also, I'm pretty sure their parts guy fradulently used my cc as right after I bought some parts I got tons of fraud calls and had to have the damn card reissued.

Is there an easy way to check the diff operation? Jack up one tire and try to spin the other type of deal? Btw, I have never tracked the car but I do take it for spirited drives wherein I driver it harder than the majority of people that track cars as I have a professional racing background. The car should be able to handle this though.

Any help is appreciated. This is really getting to be more than annoying as it's really squirly under power even in just normal driving. Thanks!

[s85e90]

It's not likely the subframe but more likely the rear control arm bushings. When you accelerate put the car in a higher gear and put the pedal to the floor while not going to fast and you'll feel the rear end wanting to wander left to right this is a big problem on the 46 chassis as well and was found to be the rear trailing arm bushings.


If you jack the rear end up and put a pry bar between the wheel and rear arms you can check to to see if it has excessive movement.

[spr]

Do you have a diagram for which arm? I'm assuming one of the uppers?

[spr]

[QUOTE=s85e90;15532523]It's not likely the subframe but more likely the rear control arm bushings. When you accelerate put the car in a higher gear and put the pedal to the floor while not going to fast and you'll feel the rear end wanting to wander left to right this is a big problem on the 46 chassis as well and was found to be the rear trailing arm bushings.

Thanks but this still doesn't likely explain the disparate traction? Or if just the right rear arm bush was bad maybe it does?

Btw. this was my initial thought as well that a camber arm or similar on the right rear was bad, but I checked same and didn't see any excessive movement about 10k miles or so ago when it was on the lift getting alignment and new tires.

[s85e90]

[QUOTE=spr;15532543]

Originally Posted by s85e90

It's not likely the subframe but more likely the rear control arm bushings. When you accelerate put the car in a higher gear and put the pedal to the floor while not going to fast and you'll feel the rear end wanting to wander left to right this is a big problem on the 46 chassis as well and was found to be the rear trailing arm bushings.

Thanks but this still doesn't likely explain the disparate traction? Or if just the right rear arm bush was bad maybe it does?

Btw. this was my initial thought as well that a camber arm or similar on the right rear was bad.

When the trailing arm bushings go bad the car will feel like its ice skating at the rear end. It will want to pull to the left or right and seem to wander. As suggested, get on parkway and put in 5-6 gear going about 50 and then press gas to floor and if it feels squirrely you know there's an issue that's not traction related.

[s85e90]

How did you check it before? You need to use a long pry bar to apply leverage against the wheel and arms to see the mpent. A little is fine. But too much means a problem.


Good luck.

[spr]

[QUOTE=s85e90;15532548]

Originally Posted by spr

When the trailing arm bushings go bad the car will feel like its ice skating at the rear end. It will want to pull to the left or right and seem to wander. As suggested, get on parkway and put in 5-6 gear going about 50 and then press gas to floor and if it feels squirrely you know there's an issue that's not traction related.

Car doesn't have trailing arms, but I assume you mean a track control arm or similar on the e9x. I'll try that. It's difficult though with the rain down here.

[spr]

[QUOTE=s85e90;15532553]How did you check it before? You need to use a long pry bar to apply leverage against the wheel and arms to see the mpent. A little is fine. But too much means a problem.

Pry bar. But I think I didn't jack it up. I don't recall offhand as I was mostly checking diff and subframe torque after an oil change.

[thekurgan]

You can test the rear locking diff if you've got the rear up on jackstands. I doubt it's toast, but some shops using too much friction modifier have basically left the locking diff as an open diff, i.e. worthless.

[s85e90]

[QUOTE=spr;15532563]

Originally Posted by s85e90

How did you check it before? You need to use a long pry bar to apply leverage against the wheel and arms to see the mpent. A little is fine. But too much means a problem.

Pry bar. But I think I didn't jack it up. I don't recall offhand as I was mostly checking diff and subframe torque after an oil change.

Yes wheels must be off the ground to check.

[spr]

Originally Posted by thekurgan

You can test the rear locking diff if you've got the rear up on jackstands. I doubt it's toast, but some shops using too much friction modifier have basically left the locking diff as an open diff, i.e. worthless.

How to tell if both are off the ground? I thought the classic test was to jack up right rear and spin it to see if it spins while left is on ground? Thanks.

[thekurgan]

Originally Posted by spr

How to tell if both are off the ground? I thought the classic test was to jack up right rear and spin it to see if it spins while left is on ground? Thanks.

Like this:

For an LSD, both wheels should spin in the same direction. If you only lift one wheel, what would happen if the grounded wheel started to move? Sounds like you could have a jackstand fail on your hands.

[Detroit M3]

dif brace from acm will do the trick.

[spr]

Originally Posted by thekurgan

Like this:

For an LSD, both wheels should spin in the same direction. If you only lift one wheel, what would happen if the grounded wheel started to move? Sounds like you could have a jackstand fail on your hands.

Your speculation is without merit as you fail to consider 3 wheels will be on the ground. It is to see if the clutches are operating.

[bigjae1976]

Bald, old, hard rear tires will have the same symptoms that you describe. Also, an out of whack rear alignment...specifically the toe. I'd look at those first.

[s85e90]

Yeah def should've mentioned to check the rear toe and get a quality alignment done first to rule out other things in the suspension

[spr]

As denoted above, I recently had alignment and have brand new rears. Further those indicia would not create such a condition.

[bigjae1976]

Originally Posted by spr

As denoted above, I recently had alignment and have brand new rears. Further those indicia would not create such a condition.

Actually, the symptoms you describe would be the result of an out of whack alignment and/or bad tires.

If those are good then I'd point to the rear suspension. I'm assuming you are doing all of this launching and wheel spinning with DSC off and not in MDM. Did you tell the service advisor what you were trying to do? I imagine the information you are giving us would lead him away from wheel speed sensors if you did have DSC off and told the service advisor.

I would guess you didn't tell the dealer that which is why they would be led to believe that you had bad wheel speed sensors.

BLUF: I smell bullshit here. Not saying its bullshit...just smelling it right now.

[spr]

Originally Posted by bigjae1976

Actually, the symptoms you describe would be the result of an out of whack alignment and/or bad tires.

If those are good then I'd point to the rear suspension. I'm assuming you are doing all of this launching and wheel spinning with DSC off and not in MDM. Did you tell the service advisor what you were trying to do? I imagine the information you are giving us would lead him away from wheel speed sensors if you did have DSC off and told the service advisor.

I would guess you didn't tell the dealer that which is why they would be led to believe that you had bad wheel speed sensors.

BLUF: I smell bullshit here. Not saying its bullshit...just smelling it right now.

Must be smelling yourself. Alignment was done with new rear PSS. I've always guessed it was a bad arm until I stuck a pry bar on there and everything looked ok which made me thing subframe bushings as others have said if the subframe moves the geometry moves which is what it feels like.

I haven't taken car in to tell advisor anything. I have to reprogram ECU and DCT first.

As to the wheel sensors you have poor reading comprehension. I previously said I had a ton of errors go off and they replaced the speed sensor nothing more. This work was prior to any issues with diff or bushes.

I'll advise once I have a free moment away from work on the bushings. Is there a way to check subframe bushes while I'm at it other than dropping? Thanks.

[bigjae1976]

Unless you can see cracks in the rubber...no way to check unless you drop the rear subframe. Hmmm...so you need to flash your ECU back before you take it into the dealer to look at an issue which...it may contribute to?

So basically you want to come here, look for a pity party, and hear about how every dealership in america is out to screw you. Then encourage you to fight the power. But now you need to remove modifications before you take it into the dealer so they don't know that you modded the car? I think they can look at that stuff. I think its a bad risk if you think a dealership won't think to look into your DME given that you are under an extended warranty.

In case you didn't know, extended warranty pricing for BMWs is going through the roof right now because companies are losing money. You had better believe that BMW service departments are under high...nay...VERY high scrutiny from the underwriters of the extended warranty. Dealerships don't want to suck up the bill so a smart dealership will tell you to pound sand. They do not exist to kiss your ass...they are there to make money.

Originally Posted by spr

Must be smelling yourself.

Seriously? I used that come back in 2nd grade. Please think of something better next time.

[rocket_science]

Same way you'd check all the other bushings... Will all due respect, it sounds like a lot of assumptions are being made without actually putting it up on the lift to give it a proper check. Why haven't you done this? I suggest you put it up, get under it, do all the appropriate standard checks and report back if you haven't found any issues.

If you don't know what a typical inspection like this entails, maybe it's best to leave it to someone who does?

[spr]

I finally got around to doing this and the arms with holes in them (trailing) were really squirmy when pushed with pry bar. Diff bushes were also very loose. I could move the sucker front and back quite easily!

Originally Posted by s85e90

It's not likely the subframe but more likely the rear control arm bushings. When you accelerate put the car in a higher gear and put the pedal to the floor while not going to fast and you'll feel the rear end wanting to wander left to right this is a big problem on the 46 chassis as well and was found to be the rear trailing arm bushings.


If you jack the rear end up and put a pry bar between the wheel and rear arms you can check to to see if it has excessive movement.