'79 300SD Engine Vibration

Hello,
I'm wondering if someone can give me advice on this problem - Recently my engine started vibrating excessively (esp. at higher speeds), whether in
neutral or on the freeway. I checked my right engine mount, which was soaked in oil from an old cracked breather hose leaking on it (which I fixed) and had the rubber tearing at the edges, so I replaced the mount. The left mount appears to be in perfectly good condition, dry, and with shield in place. However, the vibration is still there (although to a lesser extent, so I guess the new mount helped a little).
So now I'm wondering if I should have replaced the left mount as well, even though it seems to be in perfect working order, or if the engine shocks are to blame. How can I know that the shocks are bad? I couldn't tell if they're leaking anything because everything was so greasy down there (although I cleaned it up now).
Thanks!
Daniel Schuler
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It is best to replace both mounts at the same time so you eliminate the vibration problem. It may look okay... but old rubber and new rubber does not work the same.
Another vibration reason might be because of the air cleaner... rattling so it feels like a vibration.
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well i finally replaced my bracket on my 82 sd the beach towel i placed on the air cleaner top was dirty. it did work for a year though!
the case, minus a few cans!
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The engine's shocks are only effective at idle so forget them.
You say there's vibration at high engine speed. It's doubtful that the engine itself is vibrating at high rpms for even a misfire is canceled at high rpm. So the vibration you feel must be the engine bouncing about on its three mounts - left, right and transmission. The left and right motor mount pads have different shore hardness because the engine's torque pushes one down and pulls the other up so be sure the correct one is installed on each side. Each side mount has three screws: a M 12 x 40 from the bottom and two M 8 x 18 from the top. These should be torqued to 51 ft lbs.
Nice car, I've owned a '80 since new; it's air cleaner support bracket and water pump are the only engine problems that its had in 108K miles.
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I have this problem before, change all the mounts and that's it
csc

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