Rear end shake @ 50 MPH

[Fla Grown]

I just installed my rebuilt motor with new motor mounts and trans mounts, rebuilt drive shaft, new tires and the rear end shakes like crazy. It was shaking before I took the motor out for the rebuild but seems worse since I put it back together. Any ideas? Rides like a dream until I hit 50.

[vin63]

Have you had the rear tire/wheel combinations re-balanced lately? Or, checked the tires for any carcass splitting issues?

[Fla Grown]

No on the balancing. Tires are new and only have a few thousand miles on them.

[Indian113]

Have you checked pinion angle? Did it change when you lowered your truck?

[Fla Grown]

How do I check the pinion angle?

[Indian113]

I bought a cheap one at Harbor Freight. The front and rear angles should be close to being the same angle, only one should be up and one should be down.

[geezer#99]

Originally Posted by Fla Grown

How do I check the pinion angle?

It's all in this thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=569350

[Fla Grown]

Thanks for the link Geezer, that explains it all.

[Gmforce]

just another thought....if the pinnion angle turns out good..and all the other stuff is good...check for a bent axel..my last 72 had one...

[MARTYZ]

Tire balance and pinion angle are the first things I would look at, did you install adjustable panhard on the rearend when you lowered your truck, may be just the angle of the picture but the right rear seems to back in the wheel opening quite abit, this will also affect your drive line angles if drive shaft is not running straight. Just a couple thoughts

[Fla Grown]

It has a CPP rear tracking bar. Truck rear end does sit to the driverside an 1/8" more than the passenger side by measuring tire to outer fender. Also sits is almost 1/2 in lower on the passanger side. I bought it lowered with CPP parts. Sounds like it could be both pinion angle and tracking bar adjustment.

[shawno72]

Sub'd

[Ryan Hubbard]

My friend just went through this on his Dodge and he went through everything and finally found that one of his drums had thrown the weight and was out of balance. The truck would be fine until he hit 70 mph and then it would shake the whole truck.

[63burban]

Pinion angle, tire may have thrown a weight, check to make sure the tires are perfectly round, bent rim, loose wheel, bent axle, cracked/broken drum, pinion bearing will vibrate if it's bad, does the vibration change when you accelerate or back off, if so, most likely the pinion bearing, u-joint in the saddle of the yoke correctly (most common problem if you don't pay close attention on installation ) I have seen this done many times, serious vibration

[Fla Grown]

Vibration gets worse as I accellerate above 50 so I just drive 50. I've only had it back on the road for a week so I'm still workin out the bugs.

[Fla Grown]

Thanks to everyone for all the information. Love the forum, it's been a great help on my project 66!

[neto]

Have you check for vibration with the engine in neutral? Get to speed where it vibrates then place it in neutral and see if it still vibrates. Trying to rule out engine/transmission vs tires/rear end.

[61_FL_Apache]

Rotate the tires.. Move the rears to the front and see if it continues.. All new tires need some balancing, even just a little.

[Fla Grown]

Adjusted the rear tracking bar 1/8" and it made a big difference but it still has a shimmy to it.

[keeks69]

My truck did the same as well
drums may need to be balanced

[Sick5]

what kind of vibration do you get?
is it an in and out vib where it gets loud then fades and back

[Fla Grown]

Finally got some time to take it to get the tires rotated and rebalanced. We found that the rear wheel center where it fits over the hub has been ground out to accommodate a 3.5" hub. The front's are 3". So there is no way to correctly balance the wheel. Why is my rear hub 3.5" and the front are stock 3"? I don't know.

[brokenspoke]

Originally Posted by fla grown

finally got some time to take it to get the tires rotated and rebalanced. We found that the rear wheel center where it fits over the hub has been ground out to accommodate a 3.5" hub. The front's are 3". So there is no way to correctly balance the wheel. Why is my rear hub 3.5" and the front are stock 3"? I don't know.

bingo

[1966FLEETSIDE]

nice stance how low does it sit on the pic