Driveline Vibration

[meadowbrook]

Hi all.

I have been reading some of the posts on drive shaft vibration and it seems like there are a several causes:

- Poorly balanced shaft

- worn or non centered u joints

- rear end pinion angle not parallel to transmission's angle

The drive shaft is brand new (just replaced the old ball and trunnion unit with a new custom made one with cross type joints). I will return it to ensure it is properly balanced.

Since it is new, I will assume the joints are not worn

Now to the pinion angle, the car has new springs all the way around, but the engine and trans mounts are original. Could this be causing a non parallel situation between the pinion angle and the trans centerline? Can I measure this easily? Would the symptoms in the situation be similar to an out of balance drive shaft?

I am hoping the issue is the shaft, because if it is not, I am going to be out of ideas.

I did replace the parking brake drum on the trans' output shaft because the original one had a corroded sealing surface making the trans leak, but after I replaced it, I did run the engine with the trans in 3rd without the drive shaft, up to 75 MPH and felt no vibration, so I assume the replacement drum is not the cause.

Sorry for the long post. Any ideas?

[Plymouthy Adams]

your angle would have to be way off to see this error..out of phase of the joints in conjuction of wrong angles will lessen the travel and double the chance of vibration...

getting the shaft balanced will be the best choice GIVEN the joints are in phase...the angle of the engine and the agnel of the pinion should be parallel and the degrees of the shaft in drop has to also be within the limits (the above mentioned travel)..this angle will chance during driving over certain road condtions and always with load condition..

[meadowbrook]

Thanks for the response.

What do you know, I removed the 'new' driveshaft to get it rebalanced and on a whim, I put the old original one back and drove the car again.....vibration is gone:confused:

Well, I will take the new one to get balanced anyway but I am a bit confused.

[Jerry Roberts]

Thanks for the response.

What do you know, I removed the 'new' driveshaft to get it rebalanced and on a whim, I put the old original one back and drove the car again.....vibration is gone:confused:

Well, I will take the new one to get balanced anyway but I am a bit confused.

I am glad that you found the problem . When I had a drive shaft balanced , they welded a washer onto it for a weight . When you had the new shaft made up didn't they offer to balance it ? More charges of course .

[meadowbrook]

They did balance it and I did notice the washers. I just dropped it off now with the complaint of vibration. We'll see what they say. If they say there is no issue in their balancing, I will be really confused. Only thing I can think of then is the whole pinion angle is off, which is not an issue with the current ball and trunnion setup.

However, the vibration I felt was a high frequency type @ 60 and beyond, it did not change with higher speeds and did not change whether I was coasting, accelerating or disengaging the clutch. It simply started to vibrate @ 60.

I would think a vibration caused by incorrect pinion angle would be felt at lower speeds and would change with application of power.

Any thoughts?

[martybose]

Any chance that the adapters that connect to the new shaft are off-center instead of being concentric? That would sure cause a vibration that might not be apparent just looking at the shaft by itself.

Marty

[steveplym]

They did balance it and I did notice the washers. I just dropped it off now with the complaint of vibration. We'll see what they say. If they say there is no issue in their balancing, I will be really confused. Only thing I can think of then is the whole pinion angle is off, which is not an issue with the current ball and trunnion setup.

However, the vibration I felt was a high frequency type @ 60 and beyond, it did not change with higher speeds and did not change whether I was coasting, accelerating or disengaging the clutch. It simply started to vibrate @ 60.

I would think a vibration caused by incorrect pinion angle would be felt at lower speeds and would change with application of power.

Any thoughts?

Looking to see what you find out as I am battling the exact same problem now. Dropped off my driveshaft at the shop late last week and haven't heard back yet so hoping something is off there. If not I guess I will be switching the wheels front to back to see what happens there.