As a newby to the forum, I'm looking for help on an issue with my 1984 300 Turbodiesel. I have two questions:

1. and the easy one; what is the top speed on this car? Shortly after I got the car about 18 months ago, I found that the Diff. was the source of some noise and I had one exchanged with an used one. The noise stopped, but I suspect that I got an incorrect Diff. installed.

My 1985 300 SD which has CA emission controls gets 23mpg, top speed about 115 mph with lower RPM's per speed as compared to the 84.

The 84, has no polution controls and since the rear Diff. change-out only gives me a consistent 20mpg. I did not check the fuel consumption before the diff change, since my son drove the car. The engine RPM's per speed are higher then on the SD and the torque, especially felt when shifting into 2nd gear. My top speed is at close to 4300 RPM about 105 mph.

Question: Do you think I have the wrong Diff?

2. The "boner":
Ever since I have the car, it has a shaking problem, 90% of the time whilst stoopped at a red light and engine warm. The shaking feels like the engine wants to come loose and is very hard on the engine and tranny-mounts, which I have already replaced once. Needless to say, my wife is not too happy to use the car and been watched doing the shakes during stops.
I had shops look at it, they loosened each injector while running, tried to increase the idling speed as much as possible, no clues.
On many occasions, when I am stopped at a light, I can stop the shaking (nearly) by shifting into neutral, or increasing the idle speed through the footpedal, and braking at the same time.

The car runs fine otherwise, 270K miles on it doing 60 plus miles a day. Original engine and transmission, no leaaks after leak repairs a year ago. Anybody out there with some thoughts?