Body vibration at 60 mph in the 71 cuda

[67Vette427]

This car kind of sagged in the back end too with the stock 383 springs and had the vibration even then, worset. I changed to the heavy duty springs but it didn't really raise the back end. I know there are not any shims in the perches now. I know you can order the 2 degree shims. I had the posi rebuilt too because of the vibration and they said it had a lot of parts floating around in it.

The vibration is less with all the work I've done so far, the driveshaft, transmission, and springs but its still there. Its got the big joints so the swap with his Dana 60 driveshaft would work there but I think there is a length diiference between the Dana and my 8 3/4. Maybe somebodt knows for sure. I found an original 1971 Chrysler/Plymouth Service manual at a swap meet and bought it for $20.00. Its got all the level and angle measurements.

[Chryco Psycho]

the Dana has a longer pinion so the driveshaft is approx 1" shorter But it may still fit

[ShelbyDogg]

I've used a cuda driveshaft in my Challenger for testing. It was about 1-1/2" shorter and still slipped far into the tailshaft.     Has your engine been apart or do you know it's history

[Chryco Psycho]

the Cuda & Chall are 2" different as well , the cuda being the shorter car

[67Vette427]

Somebody did a complete restoration on the car that looks to be about three years old. The engine is strong and apparently rebuilt. Seems to be the truth since it runs clean, starts easy and sounds fresh. When I got it the 833 was wasted with some of the gears contacting with the cluster when they shouldn't have been. The tranny looked like it had just been put in as everything else is cherry but it looked like it had been on the Titanic. I took Chyco's advice and threw the 833 OD trans in the car which I really like. Once the car gets above 60 its great. I did around 80 or so the other day on an empty highway by the coastal mountains and it just purred along. It almost feels like a whirring vibration through the drivetrain and body.

[ShelbyDogg]

Well, Since it's rebuilt you don't know about engine balance.  Rule out the wheels,tires and driveshaft first.  I had a crazy 4-speed shifter rattle about 75 MPH and it ended up being the end of my driveshaft. When it was cut, shortened, and balanced years ago, the driveshaft shop welded the yoke on about 6 degrees offset clockwise.  I had another shop repair it for me and now I'm flying again.   How does your shifter "feel" when you're doing 80?
Rob

[67Vette427]

The shifter doesn't seem to vibrate much. Its pretty smooth at 80.

[Chryco Psycho]

Glad you likw the 833 OD , most of the people that swap them in like them

[67Vette427]

Hi.. Its up on stands. I ran it up to 4k in neutral and I could feel a slight vibration coming from the motor once it got past 3k. I put it in third gear and ran it up to 60 and the vibration was really there. I looked at both the rear wheels and when they're spinning they seem to look a little off balance, a little shakey. I'm just not sure if they should spin perfectly straight and smooth. Please let me know what you've seen. The only part of the rear end that I didn't go through was the axles and the bearings. They looked okay. Thanks for all the help.

[ShelbyDogg]

Try it again with the wheels off.

[67Vette427]

Its still there at 60 mph with the wheels off. I guess that eliminates the tires/wheels.

[67Vette427]

I just ran it again and got under the car with a stethascope. The carrier was rebuilt just a bout 200 miles ago. I can feel the vibration at the pinion housing and on the trans tailshaft yoke the most. Its feels like it vbrates more at the pinion and I can hear a little squeeking in the pinion bearing area with the stethascope. So maybe swap out the driveshafts?

[ShelbyDogg]

Try it again with the driveshaft off.
Rob





It takes balls to get under there with the engine running, doesn't it.  You need a pit like the Valvoline oil change place, in your garage to stand under it.       

It's most likely your driveshaft like it was in mine.

[67Vette427]

LOL it sure does, especially thinking that it might get vibrated off the stands I have the big heavy duty stands under it but still.... Thanks, I'll try it without the shaft..

[redtopspeedshop]

Herb McCandless himself gave me this remedy and it worked. I went through all the stuff you have on my '70 Challenger R/T 440 4-speed. I was pulling my hair out. I did exactly what Herb advised and called Eaton spring company in detroit and got a pair of their OEM replacement leaf springs. They can even get you a lower ride height if you want to end up lower than stock. There is a difference between the left and right spring and there is a huge difference in the quality of the springs you get from Mopar and the Eaton's. They use factory specs and high grade spring steel. Most importantly, they worked. No more funky drivetrain vibrations.
C-Ya,
Damon