Engine shakes while driving

Our 1995 Grand Caravan 3.3L with 4 speed Auto-Tranny shakes and rattles pretty bad while driving, but only while the gas pedal is depressed. If I let go of the gas it stops the shaking and rattling (so that rules out tires and suspension). I've also noticed that the more weight you're pulling, (6 or 7 passengers as opposed to 1 or 2) the more it shakes and rattles.
In comparison to describe it, it feels pretty much like when your washing machine goes into it's spin cycle with an unbalanced load, the faster it spins the louder it shakes.
We took it to a mechanic about 4 months ago and he replaced 2 motor mounts, (can't remember if it was the engine mounts or the tranny mounts) and the problem went away. But now is back and doing exactly the same thing. Can anyone help?

bump...anyone?

If the problem had gone away after you had replaced the motor mounts it sounds as if they may have loosened up again or the other mounts are now causing the problem why not have your mechanic check that. :lol2: Ride On, digimon

Well even after the motor mounts were replaced I could still feel that the engine or tranny (whoever is doing it) was shaking, just not as hard. So I'm not sure if it was the motor mounts after all...

If that is the case what ever is doing it may be braking the motor mounts. This may be a tranny problem. If the motor isn't miss firing that shouldn't be stronge enough to brake a motor mount. But a tranny problem might. Don't take it to Aamco big rip off. Have a good tranny shop check it out. Ride On, digimon

Sounds like it could be an unbalanced engine or torque converter.

With road speed. How about inner CV joints? Those can be a little hard to diagnose. Your washing machine description sounds just like front axles. Vibrations/Noises are the worst :(
Have fun

Hmmm...
All good points, but I think the engine is not the problem here. It starts, idles and runs pefectly, no miss firing or rough acceleration.
Now, lets go back to the original post,
"it shakes and rattles pretty bad while driving, but "only" while the gas pedal is depressed. If I let go of the gas it stops the shaking and rattling "
OK, question.
Will an unbalanced Torque Converter or Inner CV Joint do this kind of condition only when the gas pedal is depressed (engine pulling) and not while coasting?
It's like this one mechanic told us that the problem was probably caused by a lumped tire or unbalanced rim. But I told him that if that was the case, then it would be a continuous condition, because as long as the car is moving the tire will continue to turn, just like the Torque Converter or CV Joint.
I'm not trying to say anyone is right or wrong, just trying analyze your views to try and make sense here. Thank you for helping

Hello,
I had the exact same problem with my 89 GV. I replaced the halfshafts. When I removed the shafts the inner joinys just about fell apart. Outer joints will give a clunking sound when making turns. Innner joints will give you nasty vibration only when accelerating or even just a little throttle, but not when coasting. I even went and bought new tires thinking I had a separated belt in one of my tires.
Hope this helps good luck,
Dave

Oh yeah,
after replacing halfshafts I had a very smooth ride.
I would recomend replacing both shafts at same time. If you have one shaft wore more than the other you will feel a pull from one side or the other, when accelerating, pending wich one is wore

Do I have to pull the halfshafts off the car to see if they're busted?
What's the best or easiest way to find out if the Inner Joints need to be replaced?
I would hate having to go thru all the trouble of removing the CV Joints to find out that's not the issue...

Seems to me you may need a new master cylinder...and check your timing belt as well. Hope this helps.

CV axles will do exactly what you descibe. But still, I'm not under your car. Just get left and right complete reman axles. Maybe try one at a time. Can't remember how many Mopar FWD axles I've replaced. Too many. You can't usually see any wear from outside the axle.


Not brake problem and this motor has a timing chain, FYI lol

Stay cool

Another thing, bad shafts could wear out your motor mounts because they are connected to your tranny which is connected to your motor. This vibration will travel up thru all of these parts

I took my mechanic for a test drive in the minivan, and he agrees with the halfshft theory. He wants to take a closer look, but I'm really busy this week. Will try my best to get it done asap so I can post back with the outcome...

I would definitely agree with the halfshafts. Have replaced both on every (4) caravan/voyager we have owned, sometimes twice. About every 70K miles they seem to go. Granted, we live in the Pothole state, but it seems to be the average. They're not really expensive and not too difficult to put in. I don't especially like Advance Auto, but you can generally get them for about $60 each with a lifetime warranty. The warranty only gives you piece of mind that when it breaks again, you won't have to pay for the part a second time. But that's what you get when you don't want to pay for Chrysler parts!

UPDATE:
Yes it was one of the HalfShafts...
I got them both replaced together with new KYB GR-2 Struts and Shocks (read other post on it here (http://www.automotiveforums.com/vbulletin/showthread.php?t=251950)) and the front discs and pads. The vibrations are gone and the ride is superb now. I'm really happy with the way the van rides now.
For anybody with the same problem have look at your HalfShafts first.
Thank you all for all the input and advice you gave me...

I know it's an old post, but I just discovered that I never replied to this post with the outcome.
First I would like to apologize to all and let you know that I did replaced the halfshafts and the problem was gone. The van rode like a champ afterwards.
Thanks go out to all the people that help and I hope the info here can help someone on the same situation!

Were the halfshafts your problem ?

Were the halfshafts your problem ?

I did replace the halfshafts and the problem was gone. The van rode like a champ afterwards.

I 'm pretty sure that was the problem.

Seems to me you may need a new master cylinder...and check your timing belt as well. Hope this helps.

Hmmm, perhaps it might be your johnson rod needs replacement - although I've seen a few muffler gears cause this as well.....