www.jdrace.com

Hi Jim,
i have the nearly the same problem as Robert post a few month ago :
viewtopic.php?f=4&t=379

My 65 Olds start high speed vibration at nearly 80mph (4000rpm),i´m pretty sure it come from behind me,but 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??
Difficult to hear with the Super40´s !!

As like Robert say in his thread,generally i don´t get into the +80mph range very often (it´s a convertible) but i want really to fix them!!

Parts below are new:

-new Motor mounts (rubber)
-Trans mount (rubber)
-new balanced driveshaft (to 5500 rpm)
-new U-Joints
-Transm.angle 3,5 deg.down / Pinion angle 3,5
-weld brackets to the boxed frame to minimize swinging from the Trans- crossmember
-Rear end overhauled /Posi-Gears-Timken bearings-old shafts!
-UMI´s rear Uppers with spherical rod ends
-Stock reinforced lowers with poly
-Rear end rebuilt = your Posi-Gears-Timken bearings-but old shafts!

Ohh and i also change to a another sets of Rims & tires --same vibration at same speed

I testet if vibration stops throwing the car in neutral within the vibration range to eliminate the drivetrain and i notice that it doesn't´t STOP, the vibration is not so violent and loud but exists.

Jim, i think it come from the rear end (i rebuilt years ago)
-can a bent shaft be the reason (how to chech if ?)
-or anythink with the posi unit,the gears maybe...new BEARINGS????

let me know if you have an idea....

How is the front end wheel bearings? MAke sure you have not over looked that also. Vibrations are funny and will appear to be somewhere they are not.

If your UMI control ares are adjustable I would try playing with the pinion angle. SEE if you can get the vibration to change in RPM pitch anything. The carrier bearings / carrier could be floating in the saddles if the preload is not correct and snug.
Axle shaft would need to be chucked up in a lath and a dial indicator on the machine surfaces. Looking for run out on he flange where the wheel bolts and differences between the splined area to the bearing area. .005 and larger would be bad. on the bearing differences. Jim

Jim, i think i found the soulution--- one axle shaft are bent. I can see it with the naked eye.


Thanks for Input.

Wow... Hope that solves the trouble. Good that you found something at least. JIm

Jim, if you have used axle shaft( GM 10 Bolt 7,5 with 26 Spline)- give me a quote + shipping to Germany.

...let me know if you need measuremends?

Denis

Need a length on the axle - Picture sows how to measure. Jim

Jim,I thnk it´s a good investmend to spend money in a pair of step stronger Moser shafts.
But this bring me to another question :

can i install in my 7,5" GM 10 Bolt housing a 7,625" insides (posi or Trutrac) and will it be maybe strong as 8,5" if use 28 Spline moser shafts, girdle cover and maybe C-Clip Elim Kit.

Denis & thanks & and say Yes please

The strength in the 8.5 comes from the ring and pinion not the axles. The pinion shaft is 12 bolt chevy size in the 8.5.
Next the 8.5 has larger spider gears and that is essential to keeping the power to the wheels... BUT all this is a moot point when you go to the drag race track.

For the street all rears will hold up well if the parts are installed correctly and new parts are installed.

Jim i lost your Email...please contact me at : mevido@hotmail.de

thanks
Denis