Transmission "Blues" Does Not Always Engage - 85 300D - Page 2 - PeachParts Mercedes-Benz Forum

whunter · #16 04-18-2013, 11:45 AM

Quote:

Originally Posted by mach4

There actually is a way to make motor mounts last longer. The method is to fill them with the right Shore hardness urethane rubber material. By supporting the void in the mounts, the mounts will not collapse and they will last substantially longer without any adverse vibration effects.

Here is a link to how to make your own and what urethane to use - 380SL Diesel Conversion Project

I have some, and we might experiment, when he gets back home.

.

pwjeep · #17 04-18-2013, 01:43 PM

The urethane back fill looks like a great idea. We'll have to play with it. IMHO motor mounts ought to last more than just a couple of years. In thinking about it... if the backing material (urethane) is soft / hard enough the filled in area would rest against the body and block the mount from collapsing. The parts sales folks won't like this, but this should be a standard way of building a motor mount so it will last a long time.

Does anyone have any anecdotal longevity usage to report?

uberwasser · #18 04-18-2013, 01:51 PM

Not exactly related, but, do you spend part of each year in Tucson? Or was it a one time deal?

There are several of us here, just did a scrap yard run with a friend who drives a really nice '84 300D. We should all meet up some time.

mach4 · #19 04-18-2013, 02:12 PM

Quote:

Originally Posted by pwjeep

The urethane back fill looks like a great idea. We'll have to play with it. IMHO motor mounts ought to last more than just a couple of years. In thinking about it... if the backing material (urethane) is soft / hard enough the filled in area would rest against the body and block the mount from collapsing. The parts sales folks won't like this, but this should be a standard way of building a motor mount so it will last a long time.

Does anyone have any anecdotal longevity usage to report?

It's too early to have any actual evidence of longevity, as I first reported this as my strategy to prevent collapsed motor mounts on 11-29-11 (380SL Diesel Conversion Project). Unfortunately my first experiment failed miserably, as I used a Shore 75 urethane which is way, way too hard and created unbearable vibration at idle (main mounts) and at 1500-1800 rpm (transmission mount). I replaced the main mounts with a Shore 30 urethane fill in October and that's the perfect hardness. I subsequently eliminated the fill in the tranny mount although I sold it and it is still in use.

Since the fill urethane fills the entire void in the motor mount, it simply can't collapse as there is no where for the urethane to go. Obviously the cheap rubber used in today's motor mounts can deteriorate and eventually break away, but the urethane will support a significant part of the load and make them last considerably longer.

The one thing I haven't done, but probably should do, is "coat" the top of the mount in urethane as well, to shield the rubber from air, fuel and oil, the major contributors to rubber deterioration.