hey guys maybe you will be able to help me out with my van, i got a 91 chevy g20 wich ran fine untill i started moving to another city there was nothing wrong, since i moved i havent used my van for anything so it was just sitting, i went to the store today and it drive fine untill it reached around 60-70 mph, it started vibrating nothing really major but noticible, does anyone know what that might be????

Welcome to AF, bad tire, bad u joints in the driveshaft, impossible to properly diagnose from a distance.

I love those full size Chevy vans. I have owned 3 of them.

If the vibration only started after the van was sitting a while it may be tire-related.
You may just have some flat-spots on the tires. Make sure the tire inflation is correct and they may well work themselves out so the vibration will go away.

If it stays, then you may have one or more tires with a shifted belt, or a missing wheel weight.

well it hasent been sitting for a long time maybe 2 weeks, but it doesent vibrate all the time it only starts at around 60 to 70 then it goes away a little after that but i was moving from milwaukee to appleton in wisconsin and pulling a 16" uhaul trailer with a full load in the van, i love this van the motor and trans only have about 28 thousand miles on them with a 5.7 350 so i want to get it workin right.

well it hasent been sitting for a long time maybe 2 weeks, but it doesent vibrate all the time it only starts at around 60 to 70 then it goes away a little after that .
2 weeks is long enough to temporarily flat spot a tire. Since the vibration goes away somewhat as you drive it's definitely tire related. Any other mechanical vibration, like unbalanced drive shaft or wheels would not go away after you drive.

I have a Jeep with 22 year old tires and it does the same thing. At lower speeds the tire is able to flex and absorb the effects of the flat spot. At higher speeds it is moving too fast to flex enough and you feel the vibration. Since the vibration is not too bad and I am scrapping the Jeep soon, I just live with it.....

So, if I read you right, the vibration is constant between 60-70??

Below and above that it's not there??

What's it feel like to you? Is it a "buzz" or something less than that?

Do you feel it in the steering wheel, gas pedal or everywhere?

Suggestions:

1. Look at the tires very closely for abnormal wear or bulges along the tread or sidewall.

2. Rotate the tires and see if it changes anything.

3. When it's happening, put the tranny in neutral and let the motor go to idle , coasting thru the 60-70 vibration zone.

4. Post back

well i checked my tires and the tires look fine, i have bf goodrich all terrain tires so they are naturally louder then normal tires when i when i get to around 60 it starts the the faster i drive the more vibration happens. If past 70 it just gets more vibrant. I checked the transmission fluid there is fluid in there, there is no leaks anywhere, there is no leaks coming from either trans, or rear end. There is no wear on the tires, there is no vibrating in the steering wheel, but my front driverside tire is worn on the inside with wires showing. The vibration is coming from the rear. unless i think its coming from the rear thats what it sounds like.

If you think it is the rear jack up the back, ( safely) and run the truck and see what you feel. Ony way this will get fixed is on site diagnosis