2003 540i M Sport has severe bumps steer from rear end

[Mark185]

I am working my way through sorting a 2003 540i M Sport 6 spd I bought last month. It has 97K miles on it. The previous owner replaced all of the front and rear suspension bushings and the rear ball joints a year ago and drove the car minimally after that. The problem is that over road irregularities and potholes, the rear end moves around way too much. I have had a few incidences where it literally felt like it jumped sideways over a moderately bad pothole. My 2003 530i shows none of these tendencies and it has H&R Sport springs with Koni yellow shocks which is not significantly different from the M Tech II Sport suspension. Major difference between the 2 cars are the wheels and tires. The 540i has 18" M Parallels with fairly worn Michelin Pilots. My 530i has 17" Style 42s with Continental EWS Extreme all seasons.

My question is where to start looking first if the PO is truthful and all bushings and ball joints are new? I will get the alignment checked. Will worn out 18" Michelin Pilots tramline this severely? Are the subframe bushings a likely cause? I have not read much about them failing on E39s. I do know this car has been driven in 5-6 BMWCCA track events. Would that accelerate wear on the bushings with a small number of track days?

Cosmetically, this car is in great shape. Once I get the suspension sorted, this is going to be a lot of fun to drive.

[Mvibe]

I would start with an alignment, fresh set of tires, have your alignment tech inspect bushings, how are the sway bar mounts? You could always slap the 17s on go on a test drive. That would give you an idea of it's the tires or not. I'd also check the wheel hub bearing for play.

[JimLev]

Before you spend $$ on alignment I'd jack up the back and check each rear wheel for play.
Hold the tire at 9 and 3 o'clock, try to move it by pushing with one hand and pulling with the other hand.
Do the same at 12 and 6 o'clock. There shouldn't be any free movement.
Rear lower ball joints or the wheel bearings could be bad.
Is the tire pressure correct?
Subframe bushings shouldn't be shot at 97K.

[StephenVA]

Track Days....

I would also recommend a good inspection of all the rear alignment arms (Tight and torqued loaded?) as well as the rear ball joint. Many lower control arm bushing have been reported torn/worn, causing all kinds of random movement under loads (Acceleration, turning, and braking). All of these can be checked with the suspension loaded and unloaded. The rear ball joints usually cause camber changes along with the normal clunking and creaking upon failure. On my wagon I had to remove the joint itself before I could see they were was movement at 100K.
I would also check the rear sub-frame for breaks as you do have the V8 and some owners have a "heavy foot" as a WOT over humps will give loads way beyond a snap...ha haha..

[lewyd]

My 540 moved around like you are describing. Even after I put the powerflex inserts in the rear subframe mounts. It took a lot of wiggling and a friend looking but we found 1 of the rear balljoints floppy. That said.....never under estimate how much tires influence have. I'd swap wheels and tires around since you have another set available.

[johr34]

My 540 M-Sport does not do that, just as a reference point, and I have Pilot Super Sports on.

[Mark185]

I am taking mine to a specialist here in central NJ called Tyspeed. I am asking them to test drive it and inspect the suspension. I am worried that there is something wrong with the subframe. The PO told me he drove it hard and the roads in Baltimore where he lives are very rough. I should know more by Friday.

[777300ER]

Rear lower ball joints in the back. Mine did exactly the same as you are describing and that fixed it.

[Mark185]

I am working my way through sorting a 2003 540i M Sport 6 spd I bought last month. It has 97K miles on it. The previous owner replaced all of the front and rear suspension bushings and the rear ball joints a year ago and drove the car minimally after that. The problem is that over road irregularities and potholes, the rear end moves around way too much. I have had a few incidences where it literally felt like it jumped sideways over a moderately bad pothole. My 2003 530i shows none of these tendencies and it has H&R Sport springs with Koni yellow shocks which is not significantly different from the M Tech II Sport suspension. Major difference between the 2 cars are the wheels and tires. The 540i has 18" M Parallels with fairly worn Michelin Pilots. My 530i has 17" Style 42s with Continental EWS Extreme all seasons.

My question is where to start looking first if the PO is truthful and all bushings and ball joints are new? I will get the alignment checked. Will worn out 18" Michelin Pilots tramline this severely? Are the subframe bushings a likely cause? I have not read much about them failing on E39s. I do know this car has been driven in 5-6 BMWCCA track events. Would that accelerate wear on the bushings with a small number of track days?

So, I have an update and it's looking like my wallet is about to get much thinner. Tyspeed is an independent shop near me run by a young but thorough and honest staff. I had them inspect the car. They confirmed that all suspension bushings and ball joints are good. They told me there is no damping left in the front shocks. Not a surprise. They also suspect the rear diff is failing. They think the side-to-side rocking is torque shifting from left to right because something internal such as a bearing or spider gear is failing. I have to admit, I had a Corvair Corsa turbo many years ago (1975) that behaved this way for about 1000 miles before a spyder gear in its diff failed catastrophically. I have never read about an E39 differential failing like this. I know these diffs usually run for the life of the car unless abused and not getting regular fluid changes. So now, I have some decisions to make.

1. Find a used stock diff for lowest cost repair
2. Buy a rebuilt stock unit with limited slip upgrade from a place like Diffsonline ($3400 + installation)
3. Find a used M5 LSD and change the half shafts and driveshaft or modify as needed to fit ($1000 for the diff + ???)

I'm not a fan of buying a used M5 LSD diff because it may have been severely abused and undermaintained like the one I have.

[DIEGOBMW]

My DINAN 5 did this when I had 18s on it with worn Dunlops. Rear suspension tight with all new components. I went to style 95s with Continental DWS tires and all is well. So, I'd start with a set of tires or at least take the wheels/tires off your 530 and install on the 540 and take it for a spin and see any differences.

[Mark185]

My DINAN 5 did this when I had 18s on it with worn Dunlops. Rear suspension tight with all new components. I went to style 95s with Continental DWS tires and all is well. So, I'd start with a set of tires or at least take the wheels/tires off your 530 and install on the 540 and take it for a spin and see any differences.

I will definitely try that first.

[Santaclaus4]

I have two of the same car. They are identical but have differen't tire brands. The tire can make a big difference in how the car feels. I can (and have) swapped tire/wheels back and fourth between the two cars and some handling quirks follow the tires, even though they are all (8) new tires.
Also, one of my cars has worn out shocks so I too am gonna bite that bullet...

[Mvibe]

My DINAN 5 did this when I had 18s on it with worn Dunlops. Rear suspension tight with all new components. I went to style 95s with Continental DWS tires and all is well. So, I'd start with a set of tires or at least take the wheels/tires off your 530 and install on the 540 and take it for a spin and see any differences.

I had style 95s for a bit. The extra rotational mass was noticeable especially with passengers. They look amazing though.

[AngelEye5]

My car was doing this also must be the rear tires being "Cold and Low Treadlife" also need to drive carefully in rain with DSC on at all times the rear likes to come around at low speeds and don't even try high speeds.

[Mark185]

I decided to buy a used open diff for $250 from a local salvage yard and get new tires for the M Parallels. I do believe the differential is part of the problem. There were times on dry pavement on a crowned back road, that the rear end was twitching side to side for no apparent reason. The owner at Tyspeed, Tyler Pappas, drove the car and felt the same thing. He told me about a racing incident where he had contact with another car on the track where their rear wheels touched. His differential failed several laps later and when he reviewed the data, he could see that the wheel that made contact, went to zero rpm for a split second. That put a lot of stress on his differential and he believes it caused the failure. I know there are significant differences between his race car and my M Sport. For one, he has a LSD specially prepared for racing conditions. His incident took place at > 90mph. The similarities are that both his race car and my M Sport showed signs of unpredictable torque split from left to right side that caused twitchy handling that felt like bump steer. The other factor is that I know my M Sport was in an accident with the previous owner and that there were both side and rear end impacts. The bodywork repair is outstanding. The repair shop would have easily missed a damaged differential because it only becomes noticeable many miles after the car has left the shop. The last factor is that I had a differential fail many years ago on a Corvair Corsa Turbo and it also started shifting torque unpredictably from left to right prior to catastrophic failure. I was hundreds of miles from home when that happened. I don't want to risk a repeat of that.

[Mark185]

I got the car back today after having Tyspeed install the used differential and 4 new tires. The problem is fixed. I think it was a combination of bad tires and the differential. When the shop drained the fluid out of the old diff, there were a lot of metal particles in the oil so something was definitely wrong with it. I've never seen a BMW diff with < 100K miles on it wear out before. I am just glad to have caught this before it failed with a bang. Thanks for all of the suggestions. Now, it's time to renew the shocks. They are original and have little to no compression damping left.