1984 g20 has bad drive shaft vibration
 

hi all, my 1984 chevy g20 van has a bad vibration in the drive shaft area, i have checked the u joints and there is no slop in them. the center shaft support bearing looks good ( but it does have some play in the rubber mount). i have the rear end raised in the air and when run it about 35mph is when the vibration is bad. i can see it in the rear part of the drive shaft. just wondering if anyone has encountered this before? thanks.

A similar thing happened on my Astro. Coming off the transmission, in the housing is a bushing. I believe it's bronze. It has gone bad, most likely.

thanks for the reply. this a is a 2 piece drive shaft and i didnt mention that the vibration is in the rear part of the shaft. the front half seems to be spinning smooth so I dont think its from the transmission tail shaft area.

Maybe there is a similar bushing going in to the rear end.

Its hard to check the u joints. They can vibrate without hardly any noticeable play. Do you see any rusty like spray on the underside of the body above the u joint?

nope no spray above

Your drive shaft it likely bent. I had a dodge van that did the same thing. I took it to a driveshaft shop and they put it on a lathe. It had a dent in it they heated up red hot then poured cold water on the dent and it popped right out. If you have spinned your wheels on wet pavement and suddenly hit a dry patch that's all it takes to mess up a drive shaft.

well, thought i would update.I tried another driveline and same thing bad vibration at 35mph then i took the drive shaft off and put it in gear and idled it up to 35 and nothing then I took it up and about 50 and vibration. now I'm thinking its in the trans. gonna check the tail shaft for a bad bushing or bearing. I thought maybe harmonic balancer or something wrong with the flex plate but those are spinning all the time in park or in gear and i get no vibration revving in park so I'm stumped, gonna check the tail shaft i guess.