BAD Vibration

[kwplot34]

Finally got the car back on the ground yesterday after a complete rear suspension over haul, had a 4 wheel alignment done on it yesterday. Took it out today for the first drive.
I noticed if you hold the throttle steady there is a vibration,under acceleration and deceleration there is no vibration. At one point it got so bad i had to stay under 55mph to make it go away ush: after a few miles at 55 mph i increased the speed and it was gone accept for holding the throttle steady. Any suggestions on where to start? drive line angle maybe? I installed longer spring bolts to lower the rear ride height,could this be the problem?

 

[kwplot34]

Never mind,fixed it.

 

[BBShark]

What was it?

 

[kwplot34]

What was it?

Drive line angle was way off,pretty much the same at the diff and the trans tail shaft. Used some shims to tilt the diif up about 2* higher. Went out for a drive and the vibration is gone. There is still a small vibration that comes in around 100 mph, i can feel it in the shifter.

 

[TimAT]

:hunter:HA!

 

[MYBAD79]

I wonder why it was only with the throttle steady ? Bad driveline angle should make it vibrate all the time, even if you just roll downhill with the engine turned off.
Check your engine mounts...

 

[kwplot34]

I wonder why it was only with the throttle steady ? Bad driveline angle should make it vibrate all the time, even if you just roll downhill with the engine turned off.
Check your engine mounts...

I don't know Karsten. But changing the angle made it go away. Motor mounts are new. I would still like to find the vibration that comes in around 100 mph.

 

[damoroso]

Finally got the car back on the ground yesterday after a complete rear suspension over haul, had a 4 wheel alignment done on it yesterday. Took it out today for the first drive.
I noticed if you hold the throttle steady there is a vibration,under acceleration and deceleration there is no vibration. At one point it got so bad i had to stay under 55mph to make it go away ush: after a few miles at 55 mph i increased the speed and it was gone accept for holding the throttle steady. Any suggestions on where to start? drive line angle maybe? I installed longer spring bolts to lower the rear ride height,could this be the problem?

I had the same symptoms. Turned out to be driveline angle as well. I'd changed everything from the radiator to the rearend (went to a big block with a 2004r trans and a differential out of a 71, so everything changed.). Thought I had the angles right with 5 degrees down on the engine and 5 up on the differential. Nope...brought the differential down and the transmission up. Now it's like yours, but I'm sure my higher speed vibration is from the front end. I need to rebuild the front suspension.

 

[kwplot34]

Finally got the car back on the ground yesterday after a complete rear suspension over haul, had a 4 wheel alignment done on it yesterday. Took it out today for the first drive.
I noticed if you hold the throttle steady there is a vibration,under acceleration and deceleration there is no vibration. At one point it got so bad i had to stay under 55mph to make it go away ush: after a few miles at 55 mph i increased the speed and it was gone accept for holding the throttle steady. Any suggestions on where to start? drive line angle maybe? I installed longer spring bolts to lower the rear ride height,could this be the problem?

I had the same symptoms. Turned out to be driveline angle as well. I'd changed everything from the radiator to the rearend (went to a big block with a 2004r trans and a differential out of a 71, so everything changed.). Thought I had the angles right with 5 degrees down on the engine and 5 up on the differential. Nope...brought the differential down and the transmission up. Now it's like yours, but I'm sure my higher speed vibration is from the front end. I need to rebuild the front suspension.

I am pretty sure it's not my ft end,completely rebuilt it 2 years ago. I might try messing with the drive line angle a little more and see if that fix's the high speed vibration. It's not real bad vibration and i can only feel it in the shifter (4 speed manual). Pretty sure it's not the drive line,had new u-joints installed last year and had it balanced.

 

[SmokinBBC]

Finally got the car back on the ground yesterday after a complete rear suspension over haul, had a 4 wheel alignment done on it yesterday. Took it out today for the first drive.
I noticed if you hold the throttle steady there is a vibration,under acceleration and deceleration there is no vibration. At one point it got so bad i had to stay under 55mph to make it go away ush: after a few miles at 55 mph i increased the speed and it was gone accept for holding the throttle steady. Any suggestions on where to start? drive line angle maybe? I installed longer spring bolts to lower the rear ride height,could this be the problem?

I had the same symptoms. Turned out to be driveline angle as well. I'd changed everything from the radiator to the rearend (went to a big block with a 2004r trans and a differential out of a 71, so everything changed.). Thought I had the angles right with 5 degrees down on the engine and 5 up on the differential. Nope...brought the differential down and the transmission up. Now it's like yours, but I'm sure my higher speed vibration is from the front end. I need to rebuild the front suspension.

I am pretty sure it's not my ft end,completely rebuilt it 2 years ago. I might try messing with the drive line angle a little more and see if that fix's the high speed vibration. It's not real bad vibration and i can only feel it in the shifter (4 speed manual). Pretty sure it's not the drive line,had new u-joints installed last year and had it balanced.

Does it happen at the same RPM first/second/third as it does at 100mph?

 

[damoroso]

Mine was speed specific...had a couple of ranges, but around 55 was by far the worst.

 

[kwplot34]

Finally got the car back on the ground yesterday after a complete rear suspension over haul, had a 4 wheel alignment done on it yesterday. Took it out today for the first drive.
I noticed if you hold the throttle steady there is a vibration,under acceleration and deceleration there is no vibration. At one point it got so bad i had to stay under 55mph to make it go away ush: after a few miles at 55 mph i increased the speed and it was gone accept for holding the throttle steady. Any suggestions on where to start? drive line angle maybe? I installed longer spring bolts to lower the rear ride height,could this be the problem?

I had the same symptoms. Turned out to be driveline angle as well. I'd changed everything from the radiator to the rearend (went to a big block with a 2004r trans and a differential out of a 71, so everything changed.). Thought I had the angles right with 5 degrees down on the engine and 5 up on the differential. Nope...brought the differential down and the transmission up. Now it's like yours, but I'm sure my higher speed vibration is from the front end. I need to rebuild the front suspension.

I am pretty sure it's not my ft end,completely rebuilt it 2 years ago. I might try messing with the drive line angle a little more and see if that fix's the high speed vibration. It's not real bad vibration and i can only feel it in the shifter (4 speed manual). Pretty sure it's not the drive line,had new u-joints installed last year and had it balanced.

Does it happen at the same RPM first/second/third as it does at 100mph?

Only happens at 100 mph and faster.