[alex-qts]

All started under WOT last night when something definitely broke / changed, it was noticeable straight after it happened. The car has started swaying heavily to the left then back again under heavy acceleration.

Strange thing is that it doesn't do it every time but seems more apparent at lower speeds / gears - or to put it another way, high-torque situations are when it seems to be happening.

Had the front wheels of at the weekend, so going to check bolts and tyre pressure, but apart from that tyres are MPSS with plenty of tread all round.

Proper sport-road wheel alignment was done last year, could something have knocked it out by that much? Was planning to take it back again soon.

Anyone had this before, maybe some checks I could do to narrow down the issue?

[Russbmw]

Check rear springs, maybe one has snapped (suggest the one on the left).

Then check subframe mounts and bushes are ok, although it'll probably need to go to a garage for this.

[alex-qts]

Cheers I will have a look. All seems quiet as usual, no knocks or squeaks.

It's got a comp BMW warranty, but a work acquaintance runs an independent BM/merc specialist in town that I'm actually 5 minutes from tomorrow. Might get them to take a quick look, as I presume any bushes / suspension are not covered (wear and tear items). £££

[old grey steve]

If you were loading up rear and something suddenly happened I'd be looking at the issue from he rear axle

Either the rear lower hub bush has let go which will mean the rear axle will want to "steer" under load No3 below



if the above has happened listen to a squeak perhaps when you go over a speed hump

or perhaps the main rear axle bushes are shot again circled below which will lead to the rear axle perhaps twisting under load



Another issue with these cars is the demise of the top straight arm No2 pictured below these are quite common you'll feel a knocking



As stated by Russ sudden tension under load if the springs corroded may cuase it to snap (they break on the bottom pig tail coil) but the swaying you mention leads me to think you've got one of the above issue or perhaps even a combo of the above.

A good ramp inspection will soon get tohe bottom of this though the rear axle bush one is one that sometimes some struggle with

[alex-qts]

Originally Posted by old grey steve

If you were loading up rear and something suddenly happened I'd be looking at the issue from he rear axle

Either the rear lower hub bush has let go which will mean the rear axle will want to "steer" under load No3 below



if the above has happened listen to a squeak perhaps when you go over a speed hump

or perhaps the main rear axle bushes are shot again circled below which will lead to the rear axle perhaps twisting under load



Another issue with these cars is the demise of the top straight arm No2 pictured below these are quite common you'll feel a knocking



As stated by Russ sudden tension under load if the springs corroded may cuase it to snap (they break on the bottom pig tail coil) but the swaying you mention leads me to think you've got one of the above issue or perhaps even a combo of the above.

A good ramp inspection will soon get tohe bottom of this though the rear axle bush one is one that sometimes some struggle with

Really appreciate this mate, only just seen it.

I spent quite some time under the car yesterday, whilst removing the front bumper for some grille painting. I know you can't really tell when the car is on the ground but all bushes, springs, tie-rod ends and sway bars seem ok at the front - not broken broken anyway!

Also had a look under the rear at all of the items listed above, springs seem ok at the rear, but didn't really look at the bushes, checked for cracks around the subframe as I was a bit worried about that. Wiggled everything around and it all seemed pretty firm - again I imagine you have to check with the weight off the wheels?

Now I come to think of it, the rear was squeaking a bit over bumps yesterday, I reckon you might be on to something! Just need to find a garage that can take a look, everyone seems swamped at the moment, and I'm not going the BMW warranty route as it will more than likley end up being a wear and tear item

[old grey steve]

If its been squeaking Alex fair chance the hub bush has been going for some time (you'll notice this 100% over speed humps when you load the rear up)but if you felt a definite jolt or something from the rear this could of cried enough or something else may have let go as well, all you can do is check but it does sound like from your description that something in that rear suspension area has cried enough, but I could be wrong...

Best way of inspecting is on a ramp ideally rear wheels supported and free wheeling and then usually we find the answer to issues like these without much time wasted

[AWSAWS]

What about the drive shaft to the left wheel? Worn teeth? The right side might be overpowering the left?