Said It Here

Rear diff noise after rebuild on E46 M3

Peculiar noises occurring between 10 to 20 mph in gear—especially during turns or when backing off from full lock—often stem from improper backlash, incorrect preload, or fluid issues following a differential rebuild. This prevents normal, quiet operation and leaves drivers trying to isolate whether the whine or clunk is coming from the new internals or surrounding drivetrain components.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    checking the manifold gasket
  2. 2
    inspecting the y-pipe
  3. 3
    checking for a sheared off tooth from the flywheel

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/AskMechanics1 person · September 2026

Recently acquired a new to me E46 M3. I had the diff rebuilt immediately as it was leaking, and had OEM BMW parts used. The car has since developed this peculiar noise.source ↗

Only happens in gear and typically 10-20mph. It can occur during both left and right turns. Most pronounced when backing off from full lock steering. Definitely coming from the rear of the car.source ↗

Adventurous-Camp1478 · r/AskMechanics · 3 upvotes
r/MechanicAdvice2 people · September 2026

There is noise on deceleration and we are trying to figure out the issue.source ↗

Radiant-Bite-7670 · r/MechanicAdvice · 3 upvotes

Got my entire transmission replaced and the shop welded a hole in my exhaust, think they kinda made the sound worse? Now it kinda sounds like a bad belt even though I just had that replaced, pretty sure my catalytic converter is going out as well.source ↗

Brodrizzle117 · r/MechanicAdvice · 1 upvotes

This is all supposed to be new so that would suck 😕source ↗

Radiant-Bite-7670 · r/MechanicAdvice · 1 upvotes

Where this came up

People with this problem also raised