[dilligaf]

32 ford roadster highboy. 351 Ford/C 4 and a 9" Curry rear end. 4 bar with coil overs. I am getting a heavy vibration during acceleration. It is o k when in neutral or when backing off. I have replaced the drive shaft with a new aluminum balanced shaft. I have tried to set the parallel alignment of the rear end and the transmission at 3 degrees. It is as close as I can get it. I have new u-joints. Does anyone have any other ideas? Thanks.

[user151]

If the problem is in the driveshaft it is usually --
end yokes not in phase, or
lack of lubrication in the universals.

[dilligaf]

The u joints should be lubed. They are new never lube joints installed by the drive shaft company when the new shaft was made.
I do not understand what being in phase means. How do I check that?

[prostreet6t9]

A Vibration during Accel usually means you have a angle problem.

[dilligaf]

I have tried to address the angle problem. Right now I have -2 degrees on the transmission and +2 degrees on the rear end.

[user151]

Originally Posted by dilligaf

The u joints should be lubed. They are new never lube joints installed by the drive shaft company when the new shaft was made.
I do not understand what being in phase means. How do I check that?

The yokes at each end of the shaft should be in the same plane. If you had the shaft made/shortened by a driveshaft company it should be OK.

[dilligaf]

I just checked the yokes and they are both on the same plane. Thanks for the suggestions. Any more ideas.

[user151]

Vibration on accelleration problems are tough.

Possibilities:

driveshaft balance
driveshaft phase
U-joint lube

the above all sound OK here, which would leave:

out of balance / out of round tire
bad motor mount

there are others but they would not apply to a 32 highboy....

[prostreet6t9]

Take a Picture of the rear diff showing the angle of the pinion with the D/L installed and post it.
Out of phase.. Balance...out of round tire.... would be a speed related shake not a Decel or accel shake. New "neverlube" joint's are prelubed at the factory.

[dilligaf]

I have had the problem with two drive shafts. Both of them balanced. The yokes are on the same plane. The u-joints are new and prelubed. The engine is a crate racing engine from JEGS and is supposed to be balanced. The tires are new as are the rims and have been balanced. Shouldn't have a bearing on the vibration since it is only on acceleration. When just cruising along there is no vibration and none in neutral when I rev the engine or coast. I will check the motor mounts.
Thanks for all of the input. Great ideas. I know some one out there has had the same problem. I just have to find him (her).

[Putt]

Originally Posted by dilligaf

I have tried to address the angle problem. Right now I have -2 degrees on the transmission and +2 degrees on the rear end.

If I am reading this right this means the rear of the transmission is angled 2 degrees down at the back and the rear axle is angled 2 degrees up, correct? I do not think this is the correct alignment of the drive line and u-joints. The rear axle and the transmission should both have the same angle, not opposite. In other words if the trans is aimed down 2 degrees the rear axle should also be aimed down 2 degrees, they need to be parallel to each other both vertically and horizontally. The angle of each u-joint needs to be at least 1/2 degree and less than 3 degrees and they should be the same at each end.

[Centerline]

Originally Posted by Putt

If I am reading this right this means the rear of the transmission is angled 2 degrees down at the back and the rear axle is angled 2 degrees up, correct? I do not think this is the correct alignment of the drive line and u-joints. The rear axle and the transmission should both have the same angle, not opposite. In other words if the trans is aimed down 2 degrees the rear axle should also be aimed down 2 degrees, they need to be parallel to each other both vertically and horizontally. The angle of each u-joint needs to be at least 1/2 degree and less than 3 degrees and they should be the same at each end.

Not correct for a street driven car. The pinon angle needs to be parallel with the trans output shaft angle. That means trans 2 degrees down, pinion angle 2 degrees up. Having the pinion angle negative as you describe is commonly used in drag racing on leaf spring cars where you have spring wrap that allows the pinion angle to change during hard acceleration. This is not really necessary in a 4 link setup as it does not allow the pinion angle to appreciably change during acceleration.

Centerline
HotRodsAndHemis.com

"The best car safety device is a rear-view mirror with a cop in it." - Dudley Moore

[Deuce]

Originally Posted by prostreet6t9

A Vibration during Accel usually means you have a angle problem.

Originally Posted by dilligaf

I have tried to address the angle problem. Right now I have -2 degrees on the transmission and +2 degrees on the rear end.

Change the angle on the rear end. What do you have to lose but a vibration ??

[Arrowhead]

Tourqe Converter?

[Irelands child]

Originally Posted by Arrowhead

Tourqe Converter?

Yep, good possibility - either loose on the flex plate or internally broken.

Most C4 torque converters, even performance versions, are no more then a remanufactured original part - and the last C4 was made for a full sized vehicle in '83