I have a 1990 chevy conversion van with a 350 4bbl. This van has about 120,000 miles in it. It was used for its first 80,000 hauling handy cap kids to and from town. Since then My band has bought it and Have put 50,000 miles on it in 2007 pulling a trailer all around the country. While driving through Wyoming this fall it started shaking around 45-65 miles per hour. I immediately went and had the tires rotated and balanced. Took it out, and it was worse. When I realized I was not feeling it in the steering wheel so much, I made the discovery that when I let of the gas, the shaking stops. Just a little background, The exhaust is a mess with smaller pipes just sitting inside other larger pipes. But I do not think it would cause that much of a vibration. Another thing, when I put it in neutral and rev it to 3500 rpms it does not do it. This van only pulls in drive and we never drive over 65mph. Any help you could give would be awesome. thank you!

First, I would look for either the driveshaft being bent or it lost the balancing weight. You'd see a shiny spot where the weight was (towards the rear of the van) or a sizeable ding in the shaft.

The next thing I would check is the motor mounts and transmission mount. From there look for a loose torque converter or flywheel. The loose torque converter usually comes with a clunk when you turn the engine off.

Bob

I would say look for a loose or broken transmission mount first and engine mount second.
The shaking is due likely to the engine and transmission are no longer securely mounted to the frame. As you step on the gas, the engine and transmission are twisting and shifting in the loose mounts. This causes the driveshaft to temporarily become mis aligned, causing the vibration. When you let off the gas, the twisting stops and the engine/trans slide back onto the original position.

And no, the exhaust would most likely not cause this.

Thank you for your advice. The one quesion I have with the mounts though is; when I have it in neutral and rev it up to 3500 rpms, why does it not shake then?

Last night the van just started smoking and spitting out anti-freeze and was making a horrible glugging sound. Did we just lose the motor too?

Ha so if anyone has a ford Club Wagon 15 passenger they need to get rid of, I think we will be needing something soon.

Thanks Guys

Power trains not "under load" do not act like they do when they ARE under load. Trans mount is a good bet.

Jim

i agree with mr pbody

the engines mounts will cause shaking under load but not when in neutral etc

this is just how it works

check the mounts

one is probably bad or loose

check hardware for tightness

a bolt may be loose

if it only does it under load and when in motion when driving at a speed then its gonna be a mount, or driveshaft

if it does it at all speeds except sitting still, no matter if underload or coasting then check the tires and tie rods and such

there is also a slim chance it may be an issue with the engine, fuel or spark issue

but not as likely

and also torque converter shudder can do something similar

but is also unlikely in this instance

but not impossible


bobs avatar kicks ass :DD


good luck

This happened to my bro;s Chevy Astro and we did the same thing, had the tires rotated and ballanced, got worse, went for a full inspection and they found all the engine AND trans. mounts we're bad, go figure! had that fixxed and the thing is still running like a champ!

Power trains not "under load" do not act like they do when they ARE under load. Trans mount is a good bet.

Jim

If the Van is a shakin, my wallet is aching
does your band have a song with these lyrics......