STLCRZY

Notice a high speed vibration if i get into the +80mph (4000 rpm)range with my 65/455- conv. / TH400
I notice it came from behind, and i´m not sure if i hear a "DDDDRRRR" that stops if i slow down, or if its only the pulsate of vibration that cross the car?? .....soooo i checked the drivline angle first, notice the Trans was 3,5 down,as long as the Pinion was 0,5 up ( digital Tool) -

so i corrected Pinion to 3,5 up to be equal !!

NOTHING!! Vibration start at the same speed.
Change the Tires ( I talk to myself, maybe the big 295/50 are shake )

NOTHING!! Same speed same Vibration!!

The parts below are changed and now installed:
-again new Motor mounts
-againTrans mount
-weld brackets to the boxed frame to minimize swinging from the Trans- crossmember
-new balanced driveshaft (5500 rpm)
-new U-Joints
-Transm.angle 3,5 deg.down / Pinion angle 3,5 up as i say
-Rear end overhauled /Posi-Gears-Timken bearings-old shafts!
-UMI´s rear Uppers with spherical rod ends
-Stock reinforced lowers with poly

NOTHING...NOTHING..NOTHING....still the Tiger in the Trunk

I was thinking to check
- if maybe a axle bent
- if Converter not installed correct
- U-Joints or maybe on more time the rear end
(backlash-play-POSI Clutch-bearing???)

any input...any idea..let me know

sorry for my English

dmullin

Have you tried throwing the car in neutral within the vibration range to eliminate the drivetrain up to the trans. Sometimes doing this on a downgrade gives you more time to distinguish the source.

MDchanic

Yes, driveshaft and axles are both possible sources for the vibration, as are bent rims.

These things can be very hard to chase down.

You can have the driveshaft balanced, and you can remove the axles and check them for straightness.

Good luck - this is a hard one!

- Eric

STLCRZY

Yes i test ist and it doesn't´t STOP, the vibration is not so violent and loud but exists...so only the rear end can be, but which part in the rear?


HELP

garys 68&72

First, the simple stuff, check for bent wheel, fully seated/damaged brake drum.
Also, what is the driveshaft angle in relationship to the trans and diff? It should be within 3 degrees. The higher the rpm, the closer to 0 degrees it needs to be.
Just to confirm, you need to check trans, driveshaft, diff angles with the car on all 4 tires.

dmullin

Another aid in determining the source of vibration is the frequency level.
A very fast (high frequency) buzz would normally be associated with driveshaft speed vibrations. This type of vibration can be anything related to and up to (and including)the differential pinion.
Wheel speed vibration is low frequency comparatively and feels more like a shake at highway speed. Low frequency vibration could include bent axles, wheel balance, broken tire belts. Anything travelling at axle speed.
Good luck.

Rocketbrian

I had a vibration for years in my 71 SX which seem to occur from the back, as I mostly felt in the seats versus the steering wheel. After numerous attempts to fix, I took the brake drums into the dealer and had them run up on a wheel balancer, one was out an ounce and the other out an ounce and three quarters. I immediately bought new drums from them, had those run on the balancer and they came up perfect. Once installed, the vibrations were gone. Something to consider, and eliminate from your list of corrections to do. I feel for your frustrations, as it totally ruins your driving enjoyment. Good luck.

STLCRZY

Thanks for help guys!!!!!


Rocketbrian,do you remember at which speed you fell the vibration.?

Rocketbrian

Just at highway speeds, as you would experience with an out of balance wheel/tire.
So, I take it you have tried different wheels and tires on the back?
Have you spun up the rear end without the drums on to watch the axles?
Have you watched the driveshaft and pinion spinning while on jack stands?
I take from what you are saying it doesn't do it in neutral at 4,000 RPM?
Is it a vibration in the car vs a sound?
Food for thought.

STLCRZY

Solution solution: bent axle shaft

..don´t fix them but i´m pretty sure -Thanks