I have a 98 ML320 with 86K miles. While driving on the highway today I felt a significant shaking from the rear of the vehicle. I pulled over to see if I had a tire problem, nothing there all 4 tires in good shape. I started home and once above 65 mph the shaking started again, I exited the highway for local roads. At the second stopsign it felt as if something fell in the back of the truck. It did not happen at the next stop but it did happen one more time, which made me think about the transmission.

Does the ML320 have any history of transmission problems or is this something else that I need to looked into?

Pat

the 722.6 5 speed auto trans unit in your ML is a pretty durable unit. They are not immune to problems, but normally you will experience minor slippage that escalates as more mileage accrues. As all of the unit functions are governed by a control unit which is tied into the engine CAN network, anytime the transmission adaptation values go way out of specification, you will oftentimes get a check engine light with a corresponding DTC to check the trans control units fault memory. These vehicles are known for problems with the center support bearing on the driveshaft (which would cause a slight grinding/moaning noise while moving) and with slop in the transfer case which will cause a sometimes brutal grinding/vibration that can be most easily be identified by its tendancy to happen during parking lot manuevers. Without any more specific information or a visual inspection it is difficult to pinpoint exactly what might be causing this. Any unresolved issues you've had with the vehicle over the last six months would be helpful, as well any large repairs the vehicle has had. also if you could be more detailed in you description of the current fault, when and where it happens, under what conditions, where the vibration is felt, etc. hopefully we can get this resolved for you.