Willrev,
Also, check the rear differential mount for the car sitting low in the rear. If your car "squats/ rises" when you put it in forward/ reverse this may likely be the culprit. Visually, it is very hard to tell when the rubber is starting to get a little spongey. About $50 and makes a major difference.

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Sam

84 300SD 350K+ miles ( Blue Belle )

willrev, In summoning it up looks like a good suggestion, is to follow all of what these guys have come up with.

First, i'd probably try a process of elimination:

1. Check and set idle speed at 700-800 rpm and if this doesn't help;
2. Check and possilbly change the Engine Dampers and
3. Change the Motor Mounts also,
4. Change the Transmission Mount and
5. Check and possibly change the Rear Differential Mount

Also maybe getting a new mechanic or find a reputable indy in your area.
of course be expected to put out some money...

As to the sagging rear springs will do that. But don't just get any spring Brian has been doing some reaserch into them since his car needs a set also. Their are a few different springs for each model so any spring will not work. For springs I recomend getting them from the dealer that way you will get the right ones. Also replace the shocks while the springs are out their probably shot to.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I always turn my idle down once warmed up. It doesn't sound like it's too high - you think I just need to adjust my idle control so I can turn it lower yet

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

Thr touque converters on these have very low stall speeds and are trying to pull the car at idle speeds or barely above. Does your car have a tach? Too low an idle can be a bad thing too.

If your cable it tight with the idle adjusted to minimum you could adjust it a little. I like cable to have minute slack at that point and not be holding off the throttle at all times. If it isn't under tension with it at min setting then there isn't much you can do. Don't make it any looser. My 300SD exhibits those same symptoms when idle is adjusted higher than min.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

No tach on my '79 300D. I'll check the cable to see if it is slack at the lowest point.
So...since the engine is smooth (fairly) with the car in neutral or park, my motor mounts and shocks are probably OK?

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

I would say so.....thats when mine transmitted all the vibration to the chassis before I replaced them. You don't want much slack just enough that its not under tension when turned down all the way.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

A bad transmission mount CAN remedy that - it has for me.

Marshall

Try - Replacing a bad transmission mount can remedy that!

Marshall

Many OM61x engines do NOT have shocks and don't vibrate and Mercedes even states that the purpose of the shock is to minimize the convulsion at shut down, but if your engine was quieted by replacing the shocks - so be it.

Marshall

Thats the point I was making....it made a big difference on mine even with fresh mounts.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

I second that!

Kevin

I don't want to bad mouth your Indy, but I am still a little concerned about your valve adjustment causing the shakes. In neutral, the engine has no load and will seem smooth. Have you checked your valves? The reason I ask is because of going through the same thing myself recently. ( Someone had adjusted them all too tight and intake/exhaust were the same setting.) Mine had severe palsy, especially when very warm. You might be money ahead to check before putting a lot of money in "suspect" parts.

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Sam

84 300SD 350K+ miles ( Blue Belle )

The Diesel Purge is a good idea, and can be obtained (I'm pretty sure) from Fastlane-do a search,and there are even pictures of how to do it. On my 300D, the engine shock mount helped, but the big help was rebuilt injectors (***********************-sorry Fastlane, they're a lot cheaper/$42 each for rebuilt Bosch). You might want to do a compression test if a lot of blowby is present-you might want to run synthetic oil to try to unsludge your rings(I'm trying it myself). If you need help, just put out the call for whunter or autozen-they're the GREATEST! This site has saved me a ton of money on my 300D already!

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1982 300DT 190K (Diesel Purge + synthetic oil=smoothness at last!!!)
2004 Ford E-350 6.0 L PSD 227K
2006 Dodge Ram 3500 SRW HO Cummins 4X4 48RE 42K (brute force tow vehicle)
2005 Scion xB wife's rolling pop can
1993 GMC Sierra C3500 6.2 142K

Doesn't that make it tough to get the springs back in?