car vibration and what appears to be a wobble in the rear end when i accelerate...Why.

does your driveshaft have a carrier bearing? Its a piece that looks like a support that goes around the driveshaft right after is seperates into 2 pieces. The driveshaft should have no play in this bearing if pushed up and down, or side to side.

This 1987 does not have a carrier bearing....I again checked the drive shaft for play..there wasn't any play back and fourth or up and down...Help ...what is it?

The only other thing i could think of is to have the rear end checked out. Make sure the diff is good and all bearings.

the rim might be bent.

yeah like andrew said, the rear end could be loose (maybe front end too)....while the car is on still on the ground, rock the car side to side from the rear end to see if its moving side to side, if it is then check all ur control arm bushings and see if the control arms may be a little loose and need to be re-pressed or replaced.....also idk if u've done this, but while the car is off the ground, wobble the tires a bit to check for any unusual movement

had similar problem, go over 45 mph terrible vibration throughout entire car. Could find no help, finally figured out myself. worse when car drivetrain under load, (accelerating or decelerating). Here is answer that even stumped the chevy garage: Rear wheel allignment.... camber is off rear wheels should be at 0 (straight up and down) otherwise puts joints in bind, my guess is your rear tires are sucked in on bottom. Simply adjust by shortening or lengthening the rods that go from your wheel assembly to in front of the rearend (gear box). hope this helps

Ring gear backface runout excessive? Differential pinion angle ? Accelleration can affect producing troubles when either are out of spec. The experience of your technician is your help for this kind of issue. Your GM dealer has some pretty savvy guys or can send you to where they work now.

A driveshaft that has a slip yoke may have a master spline, but not always. if it is a phasing issue, accelleration can make it act up more. The universals must be the same when the cap of one is laid flat, the other caps at other points of the same shaft must also lay flat. Likeif you used some sockets as posts and the keeper was removed during the test.

Other shafts may produce a phasing issue if ride height changes. some have to be timed by trial and error to find the sweet spot, then be indellibly marked for location. When did this start ? when repairs had been completed some ? Or was it the first reason to begin repair?

The earlier mention of rear wheel align angles like camber is a very good thought. if you changed the camber, or the height has changed, it affects. So after any repair or replacement those angles can be measured and adjusted, normally the practice is to measure these last, but before the road test.

I had vibrations that could not be found in the front of the vehicle above 70 MPH. Above 70 is when it was noticeable. I put new tires on and it went away. The tread on my tires, (9 years old) had started to separate. If you can, swap tires with someone and give it a test run. Or have a tire shop check the tread caps for signs of letting go. Check the drive shaft and see if there are signs of weights being added to balance it, and see if they have come off. It could be a drive shaft or even a half shaft causing the vibration. I'd do the tire and rim check first. Also get the tires balanced.

"Feels like hesitation and vibration on accelleration" That is parts out of shape, out of true in the powertrain parts driving the vehicle, or the angles they achieve, or phasing of the members. Back face runout can assault the ears of the driver, shaft phase can cause wrap up and release, like pinion angle can. Even a dragging part or excessively warped or misaligned part can get a tight area.................What we would do is measure the frequency and amplitude, then look at what parts operate to make those readings while it is acting up. Aligning the rear camber and toe after driveshaft and powertrain angles were checked, and inspection for parts assembled out of phase. those are indicated by the symptom, "feels like it hesitates, and vibrates on accell" But then, plug wires can make a feel that could be described similarly. Notice the load required to produce it.....is it, when accellerating, Under light, medium, or heavier load ?, i would note that. a bearing that had water entry or impact damage could produce a feel like that too. more inspecting and less replacing, more swapping, can save the wasted money.

My older chevy pickup does this type of symptom when the splines are lacking grease, the leaf springs fan out, or the 5150 adult children of trablinka try playing secret mechanic. hahaha