Rear end vibration

[NCLNDYM]

I have a 72 54dr 10 all stock. Couple weeks ago my rear starting vibrating around 80mph and would go away about 82. The vibration would also occur when slowing down at same speed but in reverse from 82 to 80 then go away. Now it's happening when i slow down around 35 or so.. I looked under the rear and have no fluid leaking or grease from anywhere. Thinking it may be my wheels, I had them rebalanced and its still vibrating. What could be the problem...If the bearings in the rear are going out how can i check it. Or can it be the U-joints. I just don't see any signs of something bad.

[datzenmike]

You have 5 U joints back there, 6 if you count the one at the back of the tranny. When they go bad the unwanted clearance allows the heavy drive shafts to go off center, ever so slightly, and they wobble and vibrate.

[NCLNDYM]

Ok, so if i shake the driveshaft or axels it would rattle or have some movement right

[ggzilla]

Nah, you can't tell by shaking it.

 

This is often a problem when lowering the car as it puts the u-joints at a higher angle (which is not bad, but will make a problem more noticeable).

 

 

To test them you go by rotation and turning force:

Rotate them back and forth and round 360 degrees by hand. They should be:

* Not loose, but have a slight drag

* Absolutely smooth with no clicks or binding spots

 

If they are really bad you can tell without disassembling. Block the wheels, put in nuetral and grab each shaft and flange and see if you can move the joint rotation-wise. Good u-joints won't let the part move.

[NCLNDYM]

Ok, the car hasn't been lowered. So just go under and manually turn the shafts and feel or slight drag for good ones and clicking noises etc or play in them to find the bad joint or joints..

[ggzilla]

Yes ... but you won't be able to inspect fully (the drag/rotation part). You will be able to tell if one is grossly worn out. If you don't find anything, then take the shafts off and inspect each one individually.

[banzai510(hainz)]

I jack up car and go under there and with both hands rotate 1 wheel back and forth and look at the u joints for slop.

Also ck to make sure the U shaped washers are in the diff carrier. I seen some removed or one missing.

[datzenmike]

Maybe move the rear tires to the front just to eliminate balance or damaged tires. Look for missing wheel weights. Look for missing balance weights on all driveshafts. Look for damage on all driveshafts... like dents.

[I'm BLUE]

iin addition to the above advice ^^^ great advice ... just things to consider ...

 

--- broken steel belts in tire?

--- bent wheel? (Hit? )

--- wheel spacers issues? ( cheap ones give problems ... )

--- etc ...

[datzenmike]

Inspect brake drum for damage.

[ggzilla]

Inspect brake drum for damage

What kind of damage?

[hang_510]

I just don't see any signs of something bad.

i didnt either and a bad ujoint caused the rear end to be ripped from the crossmember.

[datzenmike]

What kind of damage?

 

The drum can heat crack and pieces come off. Some have small weights spot welded on for balance. Anything that is spinning can be a cause of vibration.

 

I had an old drum brake Pontiac. One night there was a big bang and it started shaking. I thought I blew a tire but when I slowed down it went away (didn't have a spare so closer to home I got the better) Next day couldn't find anything wrong. Drove it for a whole summer with a shimmy at 50. One day did get a flat and when the tire and rim were removed, there was a huge piece of the drum missing. Put one from a parts car on, vibration gone.

[rpowell25]

As ggzilla pointed out, slightly worn ujoints are near impossible to troubleshoot without a very close inspection...usually a tear down. If the joint is bad enough that you can see it by rotating the wheel by hand then you got lucky it hasn't come apart yet.

 

Start with the easier areas....rotate wheels, check the spacers and drums and give it a spin. If the vib continues in the same fashion I highly recommend pulling the half shafts and replacing the joints...not terribly expensive to do before a major failure occurs. While you are under there, check the drive shaft and diff for missing weights, loose bolts. How old are the ujoints on the drive train?

[datzenmike]

Good point about the diff mounting and mustache bolts.

[NCLNDYM]

All the joints are original, limping this along to i get my daily driver back, now have a whining noise when getting on freeway looping on ramps. I think I'm gonna by new rear u joints tomorrow, already picked up one for drive shaft ones.

[banzai510(hainz)]

did you look and ck?

If yes and dont seen anything obvios I dont think its a U joint.

You hear a whining noise?U joints dont make a whinning noise. gas it and let off ,if you hear a clunk it could be a U joint/diff related.

 

whinning is different

 

make sure the half shaft bolts are all tight.

[NCLNDYM]

I've looked at everything and it all looks good. I haven't shook the drive shaft or the rear shafts yet. The whining i heard for the first time today. I'm getting ready to put my new tranny in soon. Since I have it out I'll swap the new u-joints. If the tranny is causing all the noise then I have that covered. Gonna be parking her for a while I guess.

[ggzilla]

It probably doesn't need new U-joints. Every time I bought new U-joints turned out the old ones were just fine although 35 years old.

 

Better to inspect than regret. Hainz knows what he's talking about, he's driving his Datsun.