Kick from rear end when off throttle

[rbg]

I've been having this issue for quite some time and got used to it. I do not remember how it started or if I always had it, but no when I do not DD the car it annoys me even more so I decided to ask the community. The problem is pretty much as stated in the title. When I am of throttle (you kinda may have a usual clunk so I am no sure it is related) after half a second or so it feels like there is a kick somewhere is the rear part of the drivetrain. It is not too bad, but yo can definitely feel it. All the stuff I've don't in the past ~10-15k miles: diff was rebuilt by diffsonline, new bushings in the diff, poly subframe and RTABs, welded plates (there were no cracks while I was reinforcing), new central support bearing, new guibo, new trans and motor mounts, axels look fine, but I am not sure how to properly check them. At this point I don't even know where to start... Any suggestions?

[2004LSB]

Is the diff rebuilt back to stock specs? And this happens with spirited driving or even at grocery getter speeds?

All the hardware is tightened to specs? I'm thinking you can get the back end off the ground, release the parking brake, and inspect the axles (both in gear and in netrual) - - make sure there's no slack and excessive play in the diff for starters?

[rbg]

Diff was rebuild to stock specs: 3.91 + restored m3 LSD module. I approached diffsonline with this and they basically told me that "we do 2 diffs/day, we are pros so thats impossible. You can send us your diff we will open it up and if we see that it is not out fault we will charge you per hour so you most likely will be looking at another rebuild cost". It happens even at normal driving yes. I will lift up the car and will try to make a video if there is any play.

[2004LSB]

Did you install the rebuilt diff yourself back into the subframe? I'm thinking the other potential cause for this "kick" is if the diff wasn't properly bolted down. There's a very specific sequence you must follow; here's the BMW factory TIS regarding specific removal and reinstallation of the rear diff in case you need it:

https://www.newtis.info/tisv2/a/en/e...-drive/4VCEnM1

[rbg]

Yes. That’s basically sequence I did minus special Bmw jack/support. With the tolerances in the hole sizes there is not much room to do it differently from what I recall.

[beefaroni]

I have a diffsonline rebuild in my car and sometimes if i am at a stoplight and depress the clutch pedal in neutral it sounds like some wound-up torsional loading is being unloaded. I am guessing its the same sound you are referring to. I have come to terms with the reality that the engine is noisy, the drivetrain is noisy, and everything is noisy.

That said, I will not be upset if my diff suddenly explodes. At least then I can have some closure and say to myself “see, I told you that noise didn’t seem right”

it’s fine, just launch it

[kokgo20]

OP, does your passenger side output shaft has any vertical play in it?

[rbg]

I will check.Thank you.