65 barracuda vibration

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MonkeyTrev

MonkeyTrev

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So I just recently dropped the stock rearend on my 65 cuda and moved the leaf springs in to fit wider tires. I also went to a shortened 8 3/4 and put a spool in it. Everything seemed to go together just fine. Yesterday I finally got the chance to drive it up and down the street to just test the rearend. Well I hardly got over 10mph because the whole rearend was shaking so bad. Made the entire car vibrate. I was hoping someone had some ideas of what to check.
 
MonkeyTrev said:
So I just recently dropped the stock rearend on my 65 cuda and moved the leaf springs in to fit wider tires. I also went to a shortened 8 3/4 and put a spool in it. Everything seemed to go together just fine. Yesterday I finally got the chance to drive it up and down the street to just test the rearend. Well I hardly got over 10mph because the whole rearend was shaking so bad. Made the entire car vibrate. I was hoping someone had some ideas of what to check.
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What's your pinion angle? Did you have a drive shaft made up for this? Are you still using the ball and trunnion joint out of the transmission? Are the u-joints "phased" correctly? Lot's of stuff to check. Let us know.
 
what spring relocate did you use. us car has 3 positions to mount the front of your leaf. I wonder if switching positions would help you change your pinion angle, if that's the problem
 
cmac64dart said:
what spring relocate did you use. us car has 3 positions to mount the front of your leaf. I wonder if switching positions would help you change your pinion angle, if that's the problem
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It's was a kit that I had to drill my own holes in it.
 
JBurch said:
What's your pinion angle? Did you have a drive shaft made up for this? Are you still using the ball and trunnion joint out of the transmission? Are the u-joints "phased" correctly? Lot's of stuff to check. Let us know.
Click to expand...
Everything is stock except the 8 3/4. I bought new u bolts for it also. I am going to have a drive shaft made later on. I was just hoping the one in it would work to test the rearend.
 
is it your rear or front? I had a cracked K steering gear mount and the front end rattled like a comedy grocery cart wheel. Scared the crap out of me.
You can't have a ball and trunion out of phase., they only mount one way (yoke and rollers are in same plane) at 10mph, your driveshaft should be almost level with just a slight nose down at the differential. IF the rear is shaking badly, I would suspect the spool is fighting either an out of alignment rear or possibly a tire diameter difference, maybe psi is low? Spools are tough on the street.
 
At 10mph, I doubt it's anything but the tires, or the wheelnuts,lol.Are they radials and what size, and balanced tire pressures?
Put the axle on jackstands, take the tires off, secure the drums and run her up.I bet she's smooth as can be. But if not then at least you have eliminated the most likely cause.
 
MonkeyTrev said:
I am going to have a drive shaft made later on. I was just hoping the one in it would work to test the rearend.
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Let me get this straight.......you used the original drive shaft for the 7 1/4 rear bolted up to the 8 3/4 with no modifications to it; is this correct?
 
If you used your stock driveshaft from a 71/4 then that probably is you problem. It shouldn't be the right length. I agree with j burch
 
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JBurch said:
Let me get this straight.......you used the original drive shaft for the 7 1/4 rear bolted up to the 8 3/4 with no modifications to it; is this correct?
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Yes, it is the stock drive shaft from the 7 1/4. I know it isn't perfect. I'm gonna be pulling the engine and trans and will have a new driveshaft made for the new engine/trans.
 
great catch, I didnt realize the old driveshaft was not shortened! The 8 3/4 is 2.24 longer (driveshaft shorter) so the ball and trunion is bottoming at the transmission! JHC...
 
As others have said, using the old drive shaft unmodified was/is the cause of you vibration.......you can have it shortened and it will work just fine.
 
pishta said:
great catch, I didnt realize the old driveshaft was not shortened! The 8 3/4 is 2.24 longer (driveshaft shorter) so the ball and trunion is bottoming at the transmission! JHC...
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Ok, thank you for all the help. I'm learning as I go.
 
Just glad you didn't hurt the car or yourself in the matter.

Building cars are fun.... but it's more than just slapping in some parts like the Cheby guys do. Good for you for just going for it!
You did more than most would every try.
Joe
 
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