[Tiago@VRSF]

If it's thumping it's not your LSD, it's your clutch that isn't fully disengaging. I'm betting this will mostly happen on either aftermarket clutch setups. This is something to do with clutch adjustment, not so much the differential.

I'm on the Quaife and don't have this problem (stock clutch).

[dzenno]

OEM mounts still...

I've contacted and/or worked with Wavetrac, 4 tranny shops and posted/discussed on about 5 BMW forums...

Vibration is still there but can only feel it in 6th gear with the back seats in the car (as they should be, initially I had them out due to track days and being lazy to put them back in)...

All shops, including the one that took the diff out and readjusted it, said it's normal driveline vibration...now that I barely feel it I've decided it's going on the backburner...

I've had thus setup for about 3-5000km already of moderate to heavy driving...if something was bad it'd have already broke considering what i put it through, ESPECIALLY today

[dzenno]

Originally Posted by tvieira24

If it's thumping it's not your LSD, it's your clutch that isn't fully disengaging. I'm betting this will mostly happen on either aftermarket clutch setups.

I' on the Quaife and don't have this problem (stock clutch).

You a 6MT?? If you're an auto your torque converter will muffle the noise...if you're a 6MT, take your rear seats out and don't be surprised

[Tiago@VRSF]

6MT, I drive with the rear seats folded down quite often when sending out packages to the post office and I don't have the thumping noise if I shift with the clutch disengaged.

I do get the occasional thump when going from clutch disengaged to engaged but that's common on any 6 speed, not LSD related.

[dzenno]

Try shifting FAST from 2nd to 3rd at around 2000-2500rpm, full lift off throttle...I'll pay $10 if you don't get a thump doing this seats down of course...

[Tiago@VRSF]

Sure it's going to thump then but that's not exactly what you asked in your original post is it?

That's nothing to do with the LSD really, I'd notice a thump when doing that when I was on the stock differential as well. Any sudden change in load is going to cause the thump regardless of if you are shifting gears or not.

If your clutch isn't fully disengaging you'll experience a thump while shifting gears where most people wouldn't though.

[jgalaxy]

I get a mild thump when engaging 1st and reverse. Makes me insane. BMW doesn't hear a thing. Started happening recently. 36000Km. XI, CDV, BMW short shift.

[mshahidz]

Qualife LSD here... Posted in your other read a bit back, I have thuds all around, almost any gear when shifting hard, and 1/2/3 for normal driving...it's extremely annoying and I'm not sure if I'm damaging anything.

6MT
3.46 gearing
Qualife

[dzenno]

This clutch is disengaging 100%...this isn't an issue here...

I'm finally comfortable that this is the way it is with the LSD...not sure what to say about those with thumps on a stock diff...

[dzenno]

Mohamadz, you're not damaging anything...try changing the way you shift...try to speed up the revs into your shift and then shift up...works thumplessly for me everytime...been doing it for a bit like that now and can't really shift any other way now

[TMR]

I have a quife and its quiet.

[mycoupe]

Play in the backlash maybe? When you cost it the ring and pinion "loosen up", and then when you change gears, it causes the two to "catch up" and makes the small thump. Just a thought though.

[dzenno]

Why not in 5th gear? Not the diff...its somewhere else and its normal..

[anerbe]

I'm sorry to say OP, but shifting should NOT affect the rear driveine if there's not power transfer. Only time the rear should thump is when there's an removal/application of torque when reapplying the clutch.

If you are getting thumps in the rear when shifting, this means that with the clutch fully in, when you are shifting, there is some application of torque to the driveshaft from the transmission when there shouldn't be. Shifting the transmission when decoupled from the engine should NOT apply any type of force to the rear. Either there's an issue with the clutch, or there is some play in your transmission meshing which does not seamlessly change gears.

Only other potential is that the transmission always has some sort of power transfer when shifting with the clutch pressed, and factory driveline components do a good job of dampening this. I don't think this is the issue, because others with aftermarket LSD's don't have this problem.

[dzenno]

One thing you're not realizing is that there's torque in the driveline when the wheels are turning (car is coasting)...thump isn't there when you're stopped and shifting back/forth...its there when you're coasting (everything is moving in your driveline, diff, driveshaft, flywheel) just not the clutch as you've removed it by pressing down on the clutch pedal...when you shift gears with the car "moving/coasting" you're still going from load/no load on the driveline as gears catch on...given that there's some slack somewhere this "catching on" causes a thump...problem is isolating "where" the slack is present (might be a cumulative effect of multiple sources of driveline slack too)...

[roamer]

Dzenno-

I think this is where we part ways with our problems being similar. I do not have any thumping in the 3-4 shift. My thump is in 1-2 and 2-3 shifts and it seems related to torque application because full clutch application actually makes it worse (I can largely prevent the thump by only partially disengaging the clutch).

[dzenno]

Actually its exactly the same as yours You just didn't take your rear seats out so you're not hearing it...

If I speed up into the shift the thump isn't there...if I just coast at about 2500rpm and do a shift it'll thump...its the same..

[anerbe]

Originally Posted by dzenno

One thing you're not realizing is that there's torque in the driveline when the wheels are turning (car is coasting)...thump isn't there when you're stopped and shifting back/forth...its there when you're coasting (everything is moving in your driveline, diff, driveshaft, flywheel) just not the clutch as you've removed it by pressing down on the clutch pedal...when you shift gears with the car "moving/coasting" you're still going from load/no load on the driveline as gears catch on...given that there's some slack somewhere this "catching on" causes a thump...problem is isolating "where" the slack is present (might be a cumulative effect of multiple sources of driveline slack too)...

here's my thing. I don't feel any load/no load transfer when i shift gears with the clutch fully pressed in any gear. Like others have stated, I only feel/hear a thump when I press the clutch in and shift while I have the driveline completely loaded. If there was any load transfer when shifting with the clutch completely pressed, I'm sure I would feel it somehow. I've felt jolts in the driveline when shifting in other vehicles with a more worn clutch / flywheel.

If it is indeed normal to have a load applied on the driveline when shifting, the car in stock form does a great job of supressing any reaction and any slack from aftermarket components would amplify such a case. however, I am still surprised there are people who feel no impact in the driveline when shifting.

[anerbe]

also, OP, you state you don't get the thump on downshift. based off load/unload by coasting with the clutched pressed, you should also get a thump during downshift (or any shift), not just upshift. It sounds like a meshing/decoupling issue when upshifting.