The other day, I stopped at a stop, and turned right out on the main road. Accelerated in 1st, shifted to 2nd, and continued accelerating. About halfway through the gear accelerating, BANG!

Pretty loud bang. Following the big bang, it now has this horrible knocking noise. Before you all go straight to engine knock, the knocking is based on wheel speed, not engine speed. From hearing the noise in driver seat, passenger seat, and standing on the roadside as someone else drives by, it sounds like it's driver side(maybe center?). The knocking does not change if I turn Left or Right. It speeds up as the car increases in speed, and does not change as I shift through gears except to speed up as the car speeds up. The noise goes away immediately upon letting off the accelerator and is replaced with a faint, almost grinding noise..? If I depress the clutch pedal or brake, the "grinding noise" does not change.

There is no unusual noises or feel in the drivability of the car, nor in the shifting through any of the gears, or the feel of the clutch. Acceleration is still strong. There is no leaking fluids anywhere.

I pulled both front axles. Driver side CV joint was damn near the end of life. Replaced the axle, did not fix the issue. About 6 months prior I replaced driver side wheel hub/wheel bearing. I pulled the 40AMP fuse labeled ABS that supposedly "disables" the transfer case(?) and this made no change. I know the transfer cases are prone to failure but this doesn't match anything I've read from other people's symptoms. This is not a symptom I've ever experienced from a failed clutch/pilot bearing/pressure plate. Maybe flywheel? But that doesn't spin at wheel speed, rather engine speed.

Anyone else got a clue? I'm lost.
R61 Paceman S All4 6spd manual gearbox.

 

Well, for those of you who may run into a similar issue, turns out the counterbalance shaft in the transmission literally broke in half. Time to "bulletproof" I guess 🤪

 

I'm glad you were able to figure it out, but sounds pretty serious! As I approach that mileage in my R60, any idea of how or why that happened?

 

I was accelerating moderately, not aggressively, and had just shifted into 2nd gear. RPMs were in the high 3k. I don't think this was avoidable and I don't think this is a common issue. I haven't found anyone else talking about this issue.

I found someone to do the rebuild for about $2500. While he's in there, I have him converting to a single mass lightweight flywheel, and a stage 2 clutch kit. This bumped the price (parts & labor) up to $4500.

I dont know if the lift kit and big tires, or the 24lbs of boost and methanol injection, or all the spirited driving were the causes, but I was certain something was going to give out. I just thought it would be the transfer case, as those seem to be a pretty weak point..

-zac