[335dmeow]

Hey All,

New here to posting to the forums. I have searched for a little while but don't seem to be finding the problem I'm having with my car.

2010 335d with 80k miles. At about 65-75 mph, if I press down on the accelerator about 1/8-1/4 pedal for light acceleration, I can sometimes feel a loud thumping sound that causes the car to jerk a bit. Almost feels like I'm running over potholes. To me, it sounds like the differential slipping. There hasn't been a catastrophic failure YET, but the feeling is not a good feeling and I can guess that when it fails will not be a cheap fix.

With the little to intermediate knowledge I have with car problems, I'm guessing it has something to do with differential, torque convertor, transmission... something in the drivetrain.

The biggest issue is that it is not very repeatable. Sometimes I can repeat the problem several times on a highway trip for several days out of the week. Recently, I haven't been able to replicate the problem. Brought it into the shop and couldn't replicate the problem.

In addition, I had a harmonic balancer pulley in April which was a nightmare as I was on a roadtrip but was fixed. Doubting this has anything to do with the same problem.

Has anyone else had this issue? If this has been posted already, could someone link me to the thread? Thanks.

[montr]

I also had the "harmonic balance pulley". It look like that it is a common failure above 70K miles. The rubber that is glued to the pulley get unglued from the pulley.

[BB_cuda]

Originally Posted by montr

I also had the "harmonic balance pulley". It look like that it is a common failure above 70K miles. The rubber that is glued to the pulley get unglued from the pulley.

montr, are you alphabet deleted? I recall PR thinking the higher power his car makes was a contributor. He had his changed somewhere in mid 50k range.

OP, is the noise like a clunking noise? The diff (if stock) doesn't have a clutch in it to slip. Outside chance but you might check inner and outer CV joints in output 1/2 shafts from the diff. Also, perhaps u joints between trans and diff.
The CV joints will make noise under certain flex angle and when under power. Comparing this to fwd car having clicking noise but only when turning and at higher torque (just pulling away from stop sign).
Good luck and please let us know.

[Yozh]

To the OP, please distinguish the noise at idle, with gear engaged and then with vehicle moving. This way you can start narrowing down from the harmonic balance to possible suspension issues. If this problem feels like a driveline slop, please check your guibo. Item #1 here: http://www.realoem.com/bmw/enUS/show...diagId=26_0233

Its a wear item and has been redesigned for the LCI cars, but still may need replacement.

[montr]

Originally Posted by BB_cuda

montr, are you alphabet deleted? I recall PR thinking the higher power his car makes was a contributor. He had his changed somewhere in mid 50k range.

OP, is the noise like a clunking noise? The diff (if stock) doesn't have a clutch in it to slip. Outside chance but you might check inner and outer CV joints in output 1/2 shafts from the diff. Also, perhaps u joints between trans and diff.
The CV joints will make noise under certain flex angle and when under power. Comparing this to fwd car having clicking noise but only when turning and at higher torque (just pulling away from stop sign).
Good luck and please let us know.

My car is still under BMW extended warranty and not modified. The harmonic balance pulley failure and the Throttle Actuator failure happen to me at 67K miles. On this forum and another Diesel forum, I have seen other occurrence of the same problem.

At 67K miles, replaced 11-23-8-511-371 vibration damper and 2 belts, replaced Throttle Actuator 11-71-7-804-384.

[335dmeow]

Originally Posted by Yozh

To the OP, please distinguish the noise at idle, with gear engaged and then with vehicle moving. This way you can start narrowing down from the harmonic balance to possible suspension issues. If this problem feels like a driveline slop, please check your guibo. Item #1 here: http://www.realoem.com/bmw/enUS/show...diagId=26_0233

Its a wear item and has been redesigned for the LCI cars, but still may need replacement.

Thanks for the info guys. To distinguish... no noise at idle, no noise at low speeds or when initially put into gear. Only noise is rougly 65-80 mph at light acceleration i.e. 1250-1750rpm (no automatic downshift). When I press down, the car will accelerate and then it feels like something 'slips' than catches again in three or four successive 'slips'. The sound associated with these slips feels like when you run over a pothole or a big bump at highway speeds.

[Hoooper]

does it happen only when going from coasting to accelerating, or does it also happen if you have been cruising a constant speed and decide to accelerate?

[335dmeow]

Originally Posted by Hoooper

does it happen only when going from coasting to accelerating, or does it also happen if you have been cruising a constant speed and decide to accelerate?

Both coasting to accelerating and cruising constant speed and accelerating. But only light acceleration. If the car downshifts, then the jerking/thumping doesn't happen.

I'll try and post a video replicating, but it's a pretty low end thump so I'm not sure if my phone mic will pick it up.

EDIT: Another thing worth mentioning is that the low end thump isn't in unison with the wheel speed or rpms of the car. That's why I feel like something is slipping and causing the car to jerk/hesitate.

[Mik325tds]

The universal joint in the real OEM picture item 01 could be the problem, central bearing - or check your damper mounts left and right.
When I bought my car the left rear damper mounting had play which caused a clunk under certain conditions.