Ok, on to the next issue my car is having....vibrations. I'm trying to track down some vibration issues I'm experiencing around 30mph and 70mph and have isolated the problem (I think) to the rear-end. 1) I put the right-rear up on a jack and put it into gear and could feel the same vibration as when I drive the car. Moved the jack to the other side...same thing. I did notice that there's some noticeable movement in the wheels vertically, like they are out of balance or bent, but they were recently balanced. 2) I tried swapping the wheels/tires with the front with no luck. Got the driveshaft balanced and new u-joints, which did help some overall. I also checked the distance from the axle housing to each of the rear spring mount centerlines and they are the same distance, so I think my thrust angle should be ok. I don't know about my pinion angle though. 3) I can also put the car in neutral when I feel the vibrations and this makes no difference, so it's not coming from the motor. 4) When I rotate the rear wheels by hand, you can feel a slightly rough "drag" every so often. Maybe the diff is dry? Maybe a damaged bearing or gear? I haven't opened it yet to see. I'm just looking for any good troubleshooting you guys can offer. Thanks!
Balancing will not cure an out of round issue. As a shop equipment salesman once said while demonstrating a tire balancer at the shop, "This machine will balance a box, but it won't make it roll!"
Your axle bearings needs to be replaced. If you can move the tire up and down and there play replace them now. Don't drive the car or you lose your axle.
That just means it is in the rear of the car...not the front. If your steering wheel was vibrating...then it would be the front end. Now you just need to focus on the rear and find the problem.
4) When I rotate the rear wheels by hand, you can feel a slightly rough "drag" every so often. Maybe the diff is dry? Maybe a damaged bearing or gear? I haven't opened it yet to see. or maybe one of the brake drums is out of round a little...
internal differential problems hardly ever cause vibrations. the only situation where an internal problem in the differential is when the pinion become loose either from the pinion nut coming loose or the pinion bearings have severely worn out to allow substantial movement of the pinion. their will be a substantial gear oil leak out the pinion seal if this is the problem. with that said and explained. my first guess to the cause of your vibration is a collapsed transmission mount or motor mounts. these will cause a significant change in the operating angles of the u-joints and that will cause a vibration like you have described. the other occasional problem that occurs on these cars is that the wrong u joint is put in the back of the drive shaft. the u joint is a 1310 series but it requires big caps on the differential yoke side. some times people will put a small cap one in and not realize that their caps dont fit snugly in the yoke.
Maybe related... I'd been dealing with a vibration for the past year that occurred when I got above 50 mph. Just before heading out to Roundup in July I had the tires balanced and the vibration was gone. I had only put maybe 10,000 miles on the tires since they were new and balanced. Guy doing the work said just normal wear can make a tire require rebalancing. One wheel/tire actually was now in balance with all weights removed! He also showed me that two of my Cragar SSTs were not running true, probably since they were manufactured. One rim wobbled side-to-side, the other rim bounced up and down. I didn't ask why they didn't see that before since that's where I bought the tires originally....
1) Does it matter how you put the rear drums back on if they are weight balanced (they are the original drums)? I see there is a cutout on the axle hub between 2 of the lugs. Do the weights need to go in any particular orientation to that hole? 2) Is there a good way to test if the wheels are bent? If a tire shop can balance an out-of-round wheel, how will I be able to troubleshoot this? 3) The transmission mount is newish (less than a year old) but the motor mounts weren't replaced when those jackasses rebuild my motor and put it back in the car. How can I tell if they are still good? 4) What oil should I put in the rear-end if it's needed? Stock gears and I don't think the diff has ever been opened. 5) Can the torque-converter cause any of the vibration issues I'm having? Is there an easy way to check to see if this is the problem?
Oh, the reason I ask about the torque-converter is because the same shop that screwed me over with my rebuild put the torque-converter back in loose where it was flopping around when I would accelerate. Could it have gotten damaged or bent? Is there an easy way to troubleshoot this? Also, could it have bent/cracked the flex plate? Is there an easy way to tell? What about the tail housing bushing? Could it be as simple as this bushing just being worn?
