Hello, I recently purchased a 12 E350 base with 174k miles. The car has a strange rattle/grind when on the accelerator. My local Mercedes shop will be looking at it sometime next week. This morning I drove over a big puddle of water and the symptoms went away, it was very smooth. So this points to something that needs lube.. any suggestions? wheel bearings were repacked in the last month. I can do most of the work myself, but some direction would be helpful.

Thank you.

Maybe only drive on rainy days? When were the engine/transmission mounts last replaced? They may have collapsed and the water will lube the surface temporarily until they dry out again.

Will definitely check the transmission mount today, also thinking it can be the flex disk?

I can't imagine a Flex Disc causing a rattle noise or definitely not a grinding. That is easy to inspect, and unless it's cracked or badly worn I don't think that would be it. The mounts are hydraulic and if collapsed you can experience a lot of noise that comes right into the cabin.

If the flex disks havent been replaced, they are probably due now as would be the mounts (tranny and engine).

Sorry, learning every day but what the heck is a "flex disk"?

It’s mounted on the front of the driveshaft and basically isolates vibration from the connection at the transmission. It also softens the acceleration torque when you apply the gas to move out quickly. They do wear out from use since it is not a hunk of metal.