"Vin" > wrote in message
ups.com...
> I have a Grand Cherokee (1994) with 70K on it. It's one of the last
> stick shift Grand Cherokees made, and I've owned it since it was new.
> I've developed a shimmy in the drive train that feels like the engine
> and transmission want to fall out of the vehicle. It's so bad that
> I've had to pull over to the side of the highway in stop-and-go uphill
> situations and wait for the traffic to clear. Before you suggest the
> obvious, here's what I've done: new clutch (including pressure plate
> and flywheel), new shocks all around, had the motor and trans mounts
> checked - twice, plus the universals, and the brakes are new. The
> brakes are not the problem because the vehicle rolls easily on even a
> slight grade. Here's the last bit of the puzzle: when cold, it acts
> perfectly OK: no shake at all. When I've been on the highway for a few
> miles and then try to start up a hill (even a small one, like my
> driveway), then the problem shows up. The car doesn't want to move and
> the whole underside of the motor/trans shakes like crazy. When I'm
> having this problem, I can hold the car with the emergency brake and
> try the clutch - no shake at all. I've taken it to various shops and
> no one can figure it out. Any ideas out there??
>

First, ensure the bolts from engine to bellhousing have not worked
themselves loose.
Since the problem seems to disappear when the rear differential is held
by the emergency brakes, sounds like you've narrowed the problem. Check the
rear differential when it is exhibiting the symptoms to see if the
posi-traction is trying to bind up. If so, changing the grease and adding
Jeep's recommended additive for their posi-trac'n (if such exists--service
or parts manager at Jeep dealership can guide you) may solve your problem.
Good luck, s