Bad vibrations (Part 2!)

[5.7 hemi]

Why is the yoke pointing up?

 

[Glenwood]

Under load that pinion will be around up to 7* up and too far. If the angle measurements are right, the pinion should be near zero.

 

[747mopar]

You said you had new springs made? That's all it takes to throw off your angle as was the case for me. I second what others are saying about trust nobody! We have an alignment shop in my town that everybody swears by, the guy is in his 60's and has been doing it his whole life but boogered mine twice! He's gotten lazy and just doesn't care, cost me $600 worth of tires in 5 years and I'll never let him touch a car again. Having the shaft checked somewhere else along with the tires wouldn't hurt and like mentioned make sure whoever checks the shaft spins it at operating speed.

I feel for you, been there and know how frustrating it is but finding it and fixing it is pretty rewarding, keep after it.

 

[Paul_G]

Why is the yoke pointing up?

Under load that pinion will be around up to 7* up and too far. If the angle measurements are right, the pinion should be near zero.

I agree. The pinion is pointing at the trans yoke, equal but opposite. Which in theory sounds right, but in actuality as the differential gets under load the pinion will walk up the ring gear, then the angles change.

I would try shimming the diff pinion down a couple of degrees first. Then see why the trans tail is not a full 1 1/2" off center.

I fought these same vibration problems for a few years myself. It was a transplanted 360/46rh/8 3/4 where a 318/904 used to be. After setting the tail of the trans over where it should be, and getting the trans high enough, along with the yoke pointed down just right, the car is smooth as a 1972 could be. Before it would start to vibrate around 45 mph and just get worse till I let off.

 

[5.7 hemi]

Get that pinion down to about 4* and you should be good to go.

 

[Dave145]

So I need to make the pinion point downward more? Because right now it's definitely pointed up.

I guess I didn't know that the pinion angle could cause a vibration all the time. I thought they would only vibrate on Accel/decel but not at cruise unless the angle was way off.

The motor and trans sit offset in the car for sure. You can tell just by looking at the motor that it's cocked to the passenger side.

 

[5.7 hemi]

Eng/trans is supposed to be offset, your fine there. Get that pinion pointed down to 4*. You can do it by shims or cut the perches and rotate the housing down till you have 4*, then weld them back in.

You accelerate, the pinion climbs the ring gear, and should level out. You have yours already to high and it’s trying to climb, hence the vibration.

 

[Dave145]

So then to be clear, I need a 6° shim for my pinion?

 

[5.7 hemi]

That would get you in the ball park.

 

[miller]

You can tell just by looking at the motor that it's cocked to the passenger side.

That's in part of the design, to make clearance for the steering box.

So then to be clear, I need a 6° shim for my pinion?

You need shims, or the perches moved, to get the pinion setting almost level with the ground. That's about how mine is. The angles on the u-joints should be opposed, opposite one another, to get it to run true.

 

[Dave145]

Ok I will try and find a shim set for this thing. Hopefully I can find a set and this be the end of this issue!

 

[Sixpactogo]

Ok I will try and find a shim set for this thing. Hopefully I can find a set and this be the end of this issue!

If I were you, I would see what is in there for shims now before ordering new ones. In post 21, You said your pinion is nosed up 1 degree. The factory didn't do that so either your new springs did it or some previous owner added shims. Did you install the new springs? if so, you should have found the shims. Either way, something sounds fishy with your post 21.

 

[Dave145]

I installed the springs. There were no shims of any kind present.

 

[Paul_G]

When you measured the angles how was the car positioned? With the suspension sitting on jack stands? On a 4 post lift? hopefully not with the wheels hanging.

 

[Dave145]

I measured it with the weight on the wheels sitting at ride height

 

[5.7 hemi]

Post a pic, I gotta see this!

 

[Dave145]

Here's a couple of the car itself. I don't have any currently of the driveline.

 

[Dave145]

This is it at it's first cruise night!

The rear end is higher than stock by about 2" due to the air shocks.

 

[Fran Blacker]

Do you know how to measure pinion angle?

 

[5.7 hemi]

I need a side shot of the axle.