Hey guys... Since I'm not married to Diesel Chick...

What's up with the heavy vibrations coming from the transmission? Is this a serious issue with the torque converter (or something else)? Could this be an overfilled transmission?

My wife tells me she shouldn't have to put it in Neutral when she's at a stoplight. (I had to let her drive it while she got her standard 70K transmission replacement in her Chevy Truck.)

Plan to swap out fluid and filter tomorrow.

Any help would be greatly appreciated.

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will

Fathead,

Some of these screen names kind of set you back a pace when you respond....

It sounds more like an idle speed instability than a transmission issue. When you put it in neutral you take the load of running against the transmission (pump, fluid shear) off the engine. It is likely the engine speeds up a little to its normal idle speed, and then when you put it back in Drive it slows down and gets a little rough.

The idle speed on later Diesels is not manually controllable like it was on W123 240D's and some of the other models. I am not familiar with how this is done, but I am certain I have read threads on this board with the procedure listed. You might try a search on rough idle and see what you get.

You might also have some worn engine mounts. As the engine is loaded slightly the torque causes the mounts to be loaded. If one or two are bad, the mounts can transmit more vibration, and actually set up a resonant response to the engine, exagerating the engine vibration at that frequency. Most of the time mounts that are tired are visually apparent. They are cracked and flattened. In most cases the passenger side mount takes the compression loading of the torque reaction, while the driver's side will see cyclic tension and compression loads. This can cause the driver's side mount to fail early and more dramatically, even shearing all the way through.

Hope this helps, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Bad engine mounts are a common cause of excessive vibration with these engines. The rear (transmission) mount can also cause serious thumping/drumming when it goes, as it will either separate or allow enough movement when it gets soft to allow the tranny to bang up and down. Can sound like a serious driveshaft imbalance, but only on acceleration.

If the vibration lessens dramatically or disappears in reverse, the engine mounts are definitely bad.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I'll check out those mounts... I'm not sure that's it 'cause there's almost no perceptible change in RPM.

I guess a worn torque converter wouldn't shake like that, eh?

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will

Will,

Did not mean to confuse you. The mount issue is not dependent on the idle speed change from drive to neutral when the car is stopped. However, when the car is idling in neutral there is very little torque (some oscillating torque, but no real load) being absorbed by the mounts. Most of the load on the mounts in that condition is vertical, resisting gravity trying pull the engine out the bottom of your car.

When you put it in gear, the transmission tries to make the wheels turn, and the brake pedal being depressed to keep the car from moving opposes that. But the torque generated by the engine, being reacted on by the transmission and the brake, causes the engine to try to spin itself around the drive shaft. At idle this is a relatively low force, but it happens at a relatively low frequency. The motor and transmission mounts prevent that, and one (the passenger side) takes a compression load due to torque in addition to the vertical load from gravity, while the other gets slightly unloaded by the torque. Consequently, the mounts get exercised differently in this condition, and you can get a different response, especially if the mounts are getting worn out.

The added load on a worn mount can cause it to "short out" or compress enough to act like it is not really there, allowing more engine vibration to make it to the car structure. It can also change the response of the mount enough to make the typically small physical oscillations of the motor and transmission become exagerated at specific frequencies (lower frequencies are usually worse for this, which occur at idle speeds).

It sounds like changes in idle speed are not your problem and that it is more likely the mounts themselves. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

That was the best explanation of the interaction between idle and engine mounts I have ever read. Well worth the price of admission!!! Thanks.

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Orland Park, IL
1985 300SD 215,000 miles