I have 90K miles on my 2006 R53. It has a lot of slack in the driveline. It manifests itself as a jerk when I get on/off the throttle aggressively. There is no noise or clunk. I have powerflex bushing everywhere in the front suspension and fresh ball joints. The engine mounts are poly, vibratechnics along with a vip brace, it's tight( like a tiger and yes there is NVH). The engine does not move. I checked for vacuum leaks, there were none. So I replaced the flywheel with a valeo single mass (along with the clutch). The stock flywheel had about a 1/8 of a rotation of slack. Thought I solved it. It helped a little but the slack came back and might be worse than it was before. Anyone else have a similar issue? What could it be?

 

There can be several areas were slack action comes from. The diff gears maybe worn from hard use and old transmission oil. The wear caused excessive backlash on the diff gears, but also on the shift gears also. The CV joints can wear and give you the problem. The right, or passengers side carrier bearing could be walking on the axle, or just be worn out. The nuts holding the bubs can be loose and wear the splines in the hub and on the axle. These are areas that you should look at. Start at the hubs and work back. Hope this helps!
(0K miles seems low for this wear, but not knowing the year, if it is pre 2005, then trans is suspect) Lash from new is not that unusual, but is minimum.

 

Thanks Wayne. That's about what I suspected.

 

I have this exact complaint as well! Poly bushings, vibra-technics, new mounts and ball joints all around - all has helped slightly but still what feels like too much jerk/take-up in the throttle. 70k on mine. I'll let you know if I find anything as I search for possible reasons, and I'll watch here if you happen to find anything.

 

I know this might sound odd, but have you checked the upper motor mount to see if it has moved around on the top mount? I ask because after i replaced mine it moved out of place where the marks were from the old mount and was causing the motor to move when getting on the gas. I jacked the motor back up and reset it back to the old position and it went away.

 

Thanks,
I'll look at it again. I'm fairly sure it does not move. This morning I had my fiance put it in gear with the handbrake and try to drive fwd. The engine did not move. Was on the dyno a few months back and the engine moves only a tiny bit under load: https://photos.app.goo.gl/ckNwL8c5MyUgF7tU7

 

New development! I checked the axles and they seem fine. Notice a rattle at very high speed and almost full throttle. 100 miles after car started vibrating and experience loss of power and jerking. Noise appeared to be coming from transmission. Decided to drive it home. Crusing at half throttle the car is fine. Going up slight hills on the highway or accelerating at more than half throttle car has less power and loud irregular clicking is heard coming from in front of the driver(transmission?). I jacked up the driverside and in gear the wheel rotates about 45 deg. I check and the slack is in the transmission.

I don't think the clutch is slipping as the rpms don't shoot up. The loss of power makes me think something is wrong with the engine, possibly a broken valve spring but the engine revs fine out of gear and runs fine at half throttle.
The slack and the noise makes me think gearbox. Buy why the loss of power?

 

If it is clicking, a CV joint is going bad!

 

Why the loss of power? When it starts clicking and shuttering the car does not want to accelerate even with the gas pedal buried? The CV seems like it has zero play when I attempted to rotate by hand. Before it got bad I put the car wheels on blocks and had someone roll the car fwd and back so I could see if the cv had play and it seemed fine.
thanks
Ps. I​​​​​​ do have a factory LSD

 

If there's a temporary disconnect between engine and wheel speeds, I wonder if the ASC/DSC is cutting power. Did the traction dash light come on?

 

The clicking is usually a CV joint, the power loss is another problem and needs an OBD2 check for codes. You may have a plugged fuel filter, a failing fuel pump, or corroded fuel pump connector to the fuel pump. It can be located under the rear seat on the passengers side. Unplug the connector, spray in contact cleaner, plug it back in and try to make it do the same thing. The OBD2 check is the best option right off.

 

After the initial event happened the clicking, jerking and loss of power happens at the same time and never one or the other. I will check the codes. No check engine light came on any other lights.
thanks for the help!