Stick Shift Puzzle

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 thing I would do is remove the rear drive shaft and try the truck in
4wd, could also remove it and make sure the sliding portion of the shaft is
not frozen, assuming this is how it is made, not the front slip yoke but the
splined slider. Make sure to mark the yokes and flanges to reinstall in the
same position.
"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??
>



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In article . com>,
"Vin" > wrote:

> 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??

Don't fully follow the problem from the description... but for some
reason I bet it turns out to be a busted motor mount/s problem after all.

Will it 'do it' at low enough speeds where you could (very carefully,
safe and legally) drive it with the hood open, and watch and see if the
engine is dancing around?

Also, stopped with the hood open, put it in 1st, give it just a little
gas, and gently 'slip' the clutch for a second while holding the brake.
Watch the engine, it should move, but only just a little. (Compare to
another car without the prob). Repeat the same test in reverse too.

Good Luck! Let us know what you find...

Erik

"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

Erik,
Thank you for your reply. One question - when I went to get the
mounts checked for the second time, the mechanic asked 'If it's the
mounts, why wouldn't they act up when the car is cold as well as when
its warmed up?' I'll do as you suggest and check to see what things
look like myself to see if I can spot something. Thanks again for the
reply.
- Vin

Sdlomi2,
Thanks for your idea - and a good one it is. I did have the rear
differential fluid changed about 10K ago, and the wrong fluid could be
a problem. I'm going back to the shop where the change was done to see
what they used. On the receipt, it just shows that the diff. was
serviced, but doesn't say with what. The shop manual only calls for
regular "SAE 80W-90" but I'll check to see what was used. Thanks again
for the idea - no one else came up with that one.

Shep,

Good idea. The oil change shops never even think of the slip-yoke
lube. I've been doing it myself every 5K, but your question made me
look in the manual and I see that I haven't been putting in nearly
enough, so it could be binding. I'll get under there tomorrow and pump
it full to see if it helps.
- Vin

On 24 Jul 2005 20:29:02 -0700, "Vin" > wrote:

>Sdlomi2,
> Thanks for your idea - and a good one it is. I did have the rear
>differential fluid changed about 10K ago, and the wrong fluid could be
>a problem. I'm going back to the shop where the change was done to see
>what they used. On the receipt, it just shows that the diff. was
>serviced, but doesn't say with what. The shop manual only calls for
>regular "SAE 80W-90" but I'll check to see what was used. Thanks again
>for the idea - no one else came up with that one.

If both rear tires are going at the same speed then the posi plates
should not be sliding against each other and there should be no
problem from there even if it did have the wrong fluid or was
otherwise messed up. Messed up posi should really only show up during
turns or other times when the rear tires are not going the same speed
from side to side.

On 24 Jul 2005 15:25:48 -0700, "Vin" > wrote:

>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??

If I'm following this, it only does this shake while you are starting
up from a stop and only does it when it's warmed up. To me that
sounds like a clutch/pressure plate problem, perhaps they are
contaminated with oil or brake fluid (if you have a hydraulic clutch)
and it only gets "grabby" after it warms up. Lots of "good" clutches
have a slight shudder on start up so a contaminated one might have a
lot. It could also be that the clutch is binding on the transmission
shaft but again, only when hot.

In article .com>,
"Vin" > wrote:

> Erik,
> Thank you for your reply. One question - when I went to get the
> mounts checked for the second time, the mechanic asked 'If it's the
> mounts, why wouldn't they act up when the car is cold as well as when
> its warmed up?' I'll do as you suggest and check to see what things
> look like myself to see if I can spot something. Thanks again for the
> reply.
> - Vin

If it were a mount, I really couldn't see it being temperature sensitive
by itself either. But who knows... always check the simple stuff first,
mounts are simple, quick and free to check.

Question, does this vehicle have a linkage, cable or hydraulically
operated clutch? If it's linkage, the mounts are even more suspect... a
vicious cycle can sometime be created by the engine moving enough to
engage and release the clutch on it's own.

I've seen busted mounts take a toll on plastic air intake ducts of fuel
injected engines too (the big duct between the air cleaner assembly and
throttle valve.) Cracks/leaks opening and closing as the engine 'slops'
around can raise all sorts of hell if the engine is equipped with an air
flow meter. These ducts are a good thing to look at close on a regular
basis anyway, and sometime leak unprovoked.

Again, good luck, can't wait to hear the outcome!

Erik