[07Coupe335]

2007 335i with 75000 miles, runs well except for this annoying upshift
clunk from 1st to 2nd (coasting through parking lot) or 2nd to 3rd (coasting downhill) under no-load or very lightly loaded conditions.

Happens after initial startup and also after warm up. Adding a bit of throttle eliminates the issue completely. Hard acceleration is smooth, no other trans issues present.

Was considering a transmission service, fluid / filter change myself, but don't have the tools, time, or talent. BMW dealer wants $1K, Indy wants $700.

Trying to weigh whether this transmission "issue" is an omen, in need of service, or just it's nature (at this age).

Advice appreciated.

[Rob09msport]

Might just be drivetrain lash. Could be Guibo or center support bearing or very unlikely broken tranny or engine mount which you would prob have other side effects. Try putting in 6th and hitting gas then letting off to see if does it while locked in gear.

$700!?

[TCD]

My 335xi with 159k miles exhibits this behavior exactly both before and after service. I am sure it's just driveline lash.

[07Coupe335]

Thanks all. I'll do some further experimentation.

[lowrydr310]

Did you find anything?

I have almost the exact same symptoms, though I also notice it occasionally when downshifting. In addition to the conditions you described, I could be driving at a steady 65MPH and when I step on the accelerator to pass someone the transmission downshifts and I hear this same clunk, and then hear it again when I let off the gas and it upshifts back into 6th gear. But it doesn't happen all the time.

I inspected my differential mounts, transmission mounts, and giubo and all look good. I used a prybar to check the mounts and there's no movement. Surprisingly the giubo looks like it was replaced at some point by the prevoius owner - it's far too new for the age and mileage of my car.

I do have a clunk sound when changing directions, or load reversal at low speed, that sounds like someone tapped the end of an aluminum baseball bat on a concrete floor. From what I read this might be resolved by the steps in a service bulletin to grease the differential input flange. Could it be that this same free play in the input flange is the cause of the audible clunk when the transmission is shifting at higher speeds (not just the low speed changing directions)?

I haven't checked my engine mounts. I do have a vibration at idle which I suspect could be caused by worn engine mounts. I also haven't checked the center support bearing, though it is my understanding that a failed center support bearing, or more specifically failure of the rubber insert, would cause significant driveline vibration and not just clunk sounds, which I don't have.