I have read a lot of the posts about vibration. I've eliminated everything ( I think) but the bushing in the tail end of the tranny, or the tranny itself (original 72) Can the bushing be checked for slop by pushing on the front end of the driveshaft, or should I remove the driveshaft and pull on the slip yoke?
The vibration is felt at 55-65. All rebuilt rear suspension, differential driveshaft and slipjoint. Vibration is felt when shifting into neutral and engine idling (at speed, in motion) Tires are relatively new, been balanced twice, rotated.
If it's the bushing, can it be removed and replaced without removing the tranny?
The reason I think it might be the bushing is that the driveshaft had been dented, and the original slip yoke was grooved. That replacement improved the vibration by 75%, but still I can feel some.
Thanks for any advice.
pb

 

I had to use the upper half of my old pinion bushing with a new lower half to get rid of my vibration. If it gets worse when gasing it that means the pinion is rising too high.

 

If you put the tranny in "Neutral" when at highway speeds and you still have the same vibration, that limits the possibilities to tires/wheels (they are still rotating during that test), hafl-shaft U-joints [the shafts themselves are not likely to cause significant vibration unless the joints are damaged or a tube is badly dented], bearings in the differential, driveshaft U-joints, or the driveshaft (it could have thrown a balance weight; look for signs of welding points without any weight attached to it).

To diagnose those items above, start by swapping rear wheels with front wheels to see if the 'feel' of the vibration changes. If it does, it could be tires...or it could be a defective wheel where a weld seam has come loose.

Also, get under the car and grab the various driveshafts at each end (near one joint) and shake/twist it as hard as you can. If there is no looseness at all, the bearings are likely intact; but they still could be binding up [due to damage sustained when installed]. When you twist the joint at the input side of the diffy, you will be able to 'test' the input bearing and see how much backlash/slack there is in the unit. The shaft should have a bit of rotational free-play, but it should not allow any radial movement [off of centerline]. At the transmission end, that test can evaluate damage of the transmission output bearing/bushing via axial motion, as well.

If this is a relatively recent development, think back to any work that was done just prior to noticing the problem. If this vibration started 'mildly' and progessed to a more serious condition, your problem is likely due to bearing/bushing/joint wear.

I would try to rule out wheels/tires before going further. Swap wheels with someone else or another vehicle you own, if you can. My 'money' is on the wheels/tires or a "missing" driveshaft balance weight.

 

eliminate water pump and power steering pump by having a quick drive up your street without belts.

 

Putting it in neutral at highway speeds and lifting off the throttle eliminates the engine accessories, if the vibration stays the same.

 

I bought a 69 and drove it back home. I had a vibration at those speeds that I couldn't figure out. If I shifted into neutral and reved to similar RPMs, I had the same vibration. I checked everything I could think of (flywheel/pullies/motor mounts/transmission mounts/torque converter/etc.) and then I found that the bell housing bolts came loose. Tightened them up and smooth as silk. It's worth a spot check.

 

Thanks for the input guys. Gotta get it on a lift and see if I can find anything.
pb

 

negative because your speed drops instantly and its not under constant power . its not the same as when your alternator,waterpump and power steer are all isolated completely. you can do it your way if you want but its not 100 % like removing your belts as you can accelerate,decelerate and put it through the same motions as when the vibration is there.

 

You can sit in your driveway and rev the engine up [neutral] to find vibration in it [and/or the accessories]. If it vibrates there, THEN you can isolate that vibration by pulling the belts (in some planned order) to identify the culprit. But, if the engine doesn't generate the vibration...either in the driveway or at speed when in neutral gear (revved up or not)...then its NOT in the engine area.

It's possible to have some kind of 'interaction' between engine and transmission where neither unit, independently, will cause the vibration;only vibrates when they are working together under load. But, again, that would be in a 'loaded' condition when running. A loose pressure plate might be such an example.