What is the difference? Visually they seem identical...are they made from a different type of rubber or something?

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1980 300SD 237k
1983 300D 195k (sold)
2003 Chevy Silverado 190k

The exerpt from the FSM in my previous post says that "engine mounts differ with regard to shore hardness", so you're probably exactly right. Shore hardness is a way of quantifying the hardness of the material.

http://en.wikipedia.org/wiki/Shore_durometer

I'm curious just how quantitatively different these parts are, but I suspect that the shore of the rubber in these things is not something the competing manufacturers advertise.

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-Brian

1984 300SD, 375XXX miles, Light Ivory w/ Palomino TEX

Shore hardness, huh? Who knew? Interesting. I wonder if that is why when I replaced the mount on my '83 240D the one was completely obliterated and the other one (while old and ready to be replaced) was still entact and functioning.

I wonder if this applies to my model as well?

I also wonder if this is why we see complaints of mounts failing very early - some manufacturers selling the same component for left and right, when in fact they should be different.

Do your model have the anti-vibration T mount, located on the bottom of the engine behind the oil pan. I also changed that mount on mine because it was deteriorated due to an oil leak. (Or maybe it was just really old like everything else on the car).

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'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
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"Back off, man. I’m a scientist” ~ Peter Venkman