73 Dodge Dart Sport rear end shimmy

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oneno

oneno

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Shortly after mounting new Cragar ss's after cruising at 55 for a few miles, you can start to feel a slight shake that slowly and progressively get worse to the point you have to pull over and stop, then it goes away until you cruise at 55 for a few miles then...repeat. The wheels and tires are new and balanced, front end recently aligned, just added a set of shims to the leaf springs to level out the drive shaft. It has air shocks. Very frustrating, only started doing this within 2 hundred miles as we only drive too and from regional/local shows. Any Ideas? where do I start?
Thanks in advance.
 
Did you read the leaf spring shim thread? Make sure your leaf spring bushings haven't turned into dust.
 
tekslk said:
Also double check your lug nuts.
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+1.

Also not a bad idea to take the wheels off and look at the mating surface between the wheel and the brake and make sure there's nothing odd...or a forgotten washer on one of the studs.

Always check the obvious stuff first.

Possibly dumb question- are these "universal bolt pattern" Cragars by chance?
 
Could be a bad shock also.
Raise the rear end and run it up to speed, just in case it's something you might be able to see.
 
just added a set of shims to the leaf springs to level out the drive shaft.
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Explain "level out the drive shaft".

It could be you changed your pinion angle unnecessarily.
 
if its the small bolt pattern cragers my bet is on lug nuts. the washers that come with the lugs mushroom out around the shank and up around the hex portion. they will eventually wallow out so bad that the lug pushes thru. i had a set of these on my dart that did that.
 
younggun2.0 said:
if its the small bolt pattern cragers my bet is on lug nuts. the washers that come with the lugs mushroom out around the shank and up around the hex portion. they will eventually wallow out so bad that the lug pushes thru. i had a set of these on my dart that did that.
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Interesting...

His car is a '73 so it's unlikely that he switched to small bolt pattern but couldn't this happen to the large pattern wheels too? I assume they use the same hardware.
 
MRGTX said:
Interesting...

His car is a '73 so it's unlikely that he switched to small bolt pattern but couldn't this happen to the large pattern wheels too? I assume they use the same hardware.
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the small bolt pattern uses 7/16 studs. the large uses 1/2" studs. i would check the lug washers though. the ones i had were about 1/8" too large of inside dia. for the lug shank. they were also very soft metal.
 
pull the shims out and see if it goes away.

did you check the pinion angle both before and after?
 
it seems there is always a slight vib with the slotted cragers but not as bad as you say .do you have the right nuts and washers and torque them to 80 - 85 ft lbs 30 ft lbs at a time then retorque after the first and second rides .
 
oneno said:
Shortly after mounting new Cragar .
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I think you answered your own question. Get some different tires and wheels IE "stock steelies" or others that you know worked and confirm.

Take a careful look at how the wheels are installed. Sometimes there are weights welded to the face of the drum which did NOT contact other wheels but might interfere with certain wheels.

And as suggested, take a good hard look at nuts/ washers.

Above all, do not drive it in this condition

3045d06e-4b60-11df-bb5b-001cc4c002e0.preview-300.jpg
 
67Dart273 said:
I think you answered your own question. Get some different tires and wheels IE "stock steelies" or others that you know worked and confirm.

Take a careful look at how the wheels are installed. Sometimes there are weights welded to the face of the drum which did NOT contact other wheels but might interfere with certain wheels.

And as suggested, take a good hard look at nuts/ washers.

Above all, do not drive it in this condition
Click to expand...

Agreed, but did he add the shims at the same time?
 
Finally got it back from body shop after a paint touch up. Going to start looking at all of the suggestions listed above. btw, the shims were added after the vibrating and before the wheels.
 
Once again were not getting the COMPLETE story. You said it started with the new wheels and tires in your first post, now in post #16 you say it was vibrating before the new wheel/tires and the shims?
 
I guess I should have elaborated further. Until this point I had only driven the car locally and in town, so after we had mounted the new wheels was the first time we had taken it above in town speed, so we had experience some low mph vibration but the shimming took care of that. So I'm only speculating as to when exactly it started? it could have been from the very beginning but did not notice till we got it sustained a speed above 50. Have had allot of heavy personal life events since I originally posted the topic, so sorry if I offended someone with what at first blush looks like a conflicting back story, but I do appreciate all constructive input.
 
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