pointman

in my ml i have a very hard thud when driving slow...it happens from first to second gear. any fixes? is this a serious problem?
ive heard there is a bulletin about this issue in the ml's.

m444

It sounds like early lockup of the converter lock up clutch.

pointman

interesting, thanks.

csumt76

Definitely not the converter lockup clutch. At slow speeds in second gear, if the lockup clutch is locked, you would most likely be doing less than 15-20mph with no torque multiplication from the converter. The truck would feel like a dog when accelerating.

If it is a hard thud... it could be a trans problem like valve body or the clutch pack, or even a cracked/broken engine/transmission mount.

m444

How hard of a thud is it?

If a delay accumulator filled too fast in the valve body, one could have this problem. This would feel like a shift kit in a very aggressive programmed valve body.

There is normally a pressure regulator, to limit pressure in valve body fluid circuits, if a piston was sticking, you might feel, this problem

I had a higher stall converter in a Ford, when, the converter locked at slow speed speed, it would have a very annoying thud. I had it changed (ECU) to not lockup below 45mph, no more thud.

pointman

m444, the thud is noticeable to passengers as well... it seems as though it happens when driving slow in a parking lot when looking for a parking spot. cars in 1st...then rpm rise...feels like should shift to 2nd but doesnt til later on...then after rpms rise some more, then clunk! into second with a thud.

m444

It does sound like a sticky piston in the valve body. Pressure builds, but piston does not move until, full pressue is reached, then slam.

Time for a fluid change and overhaul of the valve body.

Find someone that really knows MB automatics.

pointman

i'm still under warranty, and the dealer is saying they dont see anything wrong.

csumt76

The reason I said engine mount is because I personally have had two ML, one a 430 and one a 500 that had a broken driver side engine mount. The two pieces brake apart and it makes a thud like that. Maybe suggest that two them.... or you can check it yourself. You will need two people, put the car in drive with the parking brake applied. Then hold your left foot on the brake and give it gas with your right. If you notice excessive torqueing of then engine, it shouldn't move that much, that is your problem. Just a suggestion.

pointman

thanks for the tip, but i know its not the motor mounts and break torquing the truck isnt gonna help. its definitely tranny related.

fixedhalo

sounds like thers a fluid blockage somewhere, happend in my old car, felt like your dumping the clutch on a standard trans @ over 5k rpm right? I'm no tech, but I could suggest having the fluid checked for metalic shavings etc...if thats the case then you may need a new trans.

pointman

thats exactly what it feels like! my dealer is trying to avoid this situation like the plague.

m444

I would not expect the motor mount to fail, unless, it was defective or very old.

Put it in first gear, accellerate and de-accellerate, you should feel it knock, if it's the motor mount..

If it's under warranty, the dealer should fix it..

One could always get another opinion, different dealer or a reputable trans shop.

midget fidger

The dealers never seem to fix bad motor mounts. Search through the W208 section - MANY went to their dealers reporting unusual steering wheel vibration at idle. None of the dealers fixed it and they all said that it was "normal." I guess a few of them took it to an independent shop and got it fixed there. I figured the vibration was normal so didn't bother to tell my mechanic about it but I went on vacation, left my car with my Sister, she drove it and told my mechanic about the vibrations, he saw that it was torn to pieces and replaced it.

pointman

hmmm... ill keep you guys updated if it gets fixed. thanks for the suggestions.

csumt76

The ML 500 I mentioned had the driver mount torn in half, was an 03 model and had about 20K on it. At my dealer, we don't hesitate to replace engine mounts.