Weird noise/vibration in cabin at high speeds - *SOLVED*

[jayjpl]

Hey all,

I’ve been trying to track this noise down for a while and no luck.

Noise only began after I swapped from +22 18x9.5 square 12mm spacer setup to a style 68 non-m wheel setup with 20mm spacer in rear for winter. Swapped to 18x10 NT03+M +25 square +12mm spacer, and the noise is still there.

At speeds below 120km/h everything is normal, sounds good, feels good no problems. Speeds 110-130km/h, vibration/loud noise resonating through the cabin.

Speeds 140km/h+ its a raspy noise, and also becomes worse, loud noise/vibration still there but worse.

had someone try it out and look over the bearings, all are good, but i was positive it was the FR.

Wheels are balanced and tires are good.

Replaced front right wheel bearing, nothing, sound still there.

Had a mechanic sit in it and he thinks it was the driveshaft as i recently got a manual swap (but the noise was before the swap)

Had another mechanic sit in it, and he things the clutch packs are not disengaging in the diff, suggested I try changing the diff fluid.

Changed diff fluid with redline 75w140, did figure eights to break in the fluid, noise still there.

I tested to see if its the drivetrain by popping the car into neutral at 120+, noise is still there, regardless of whether or not foot is on the throttle.

What confuses me now, is that when i turn right at 120+, noise is still there, when i turn left, noise is completely gone. Rear right wheel bearing?

I’m confused and this thing is driving me mad, any help is greatly appreciated.


June 14th, 2021 - *SOLVED*

I got a new steering wheel for her and got an alignment because my toe was off, also had a driveshaft bolt put in as one fell out.

Sure enough, my issues are solved. I am both ecstatic and livid, but now breathing a sigh of relief.

PSA, get your driveshaft to your diff bolts tightened and checked often.

[kokgo20]

Have you checked your wheels if they are bent?
did you try removing the spacers and try?

[jayjpl]

Have you checked your wheels if they are bent?
did you try removing the spacers and try?

Yep, got the wheels checked and they are still in great shape.

Removing spacers is next on my list for sure

[Arith2]

Have you checked your alignment and for feathering on the front tires? Adding spacers should be followed by an alignment. Try driving without the spacers.

[jayjpl]

Alignment done recently, removed spacers too and its the same.

Did an inspection, my diff has a bit of backlash, and the rear exhaust hanger is unfortunately shot, once i hit around 140km/h it sounds raspy and metallic, so i’m going to replace the hanger first before looking more into a diff!

[jayjpl]

turns out exhaust hanger was just hanging on by one side and a bolt was missing, replaced the bolt, helped with noise but its still there.

Will be trying wheel bearing first before replacing the diff.

[antknee]

try swapping back to the old wheels to see if the sound is still there. I was going nuts once on my E30...no bends on the wheel, thought the tires were balanced...steering was all funky. tried a diff set of wheels/tires & everything went away. Turned out i had a faint 12inch tire bubble going 1/4 around the inside wheel, which threw off everything.

[Obioban]

If the noise was the diff, the fluid that would solve it is the OE fluid with FM booster-- the redline fluid without would likely create noise.

[jayjpl]

If the noise was the diff, the fluid that would solve it is the OE fluid with FM booster-- the redline fluid without would likely create noise.

So the noise is both noise and vibration. Its a bit of both and it gets pretty aggressive past 140 km/h, vibration is felt through entire cabin. Do you think the OE fluid with FM would help with vibrations through the cabin as well?

[Obioban]

So the noise is both noise and vibration. Its a bit of both and it gets pretty aggressive past 140 km/h, vibration is felt through entire cabin. Do you think the OE fluid with FM would help with vibrations through the cabin as well?

Normally the noise the FM booster can address is low speed steering lock turns-- not high speed. I suspect it won't, but the Redline fluid almost guarantees a noisy diff.

[jayjpl]

Normally the noise the FM booster can address is low speed steering lock turns-- not high speed. I suspect it won't, but the Redline fluid almost guarantees a noisy diff.

Ah unfortunate. I'm alright with a whiney diff at low speeds, just the vibration really bugs me. Fingers crossed the bearing fixes the noise/vibration.

[jayjpl]

update: not the rear left wheel bearing, got it replaced and noise is still there, no improvement.

Leaning towards differential now as mine has quite a bit of backlash and groans a lot at low speeds.

[Obioban]

Try the FM fluid. Cheap/easy check. Should at least address your low speed groan.

[WoGGo]

Try the FM fluid. Cheap/easy check. Should at least address your low speed groan.

If adding Friction Modifier, which would you recommend?

[Obioban]

If adding Friction Modifier, which would you recommend?

I’d get the stock Bmw fluid, pre mixed.