Driveline vibration driving me nuts

[74BlueFish]

In earlier posts I d described my upgrade to a Dana 60,   since then I have a bad vibration.  Before the upgrade from the 8 3/4 no problems.  I put all new bearings in the Dana 60 and set the backlash.  I had the driveshaft shortened.  I welded in the perched I thought at the same angle but could have messed up.

 Vibration starts at 40 mph or so and is very bad at 70.  It is speed related cause I push in the clutch and coast and the vibration doesn't change.   My transmission was 4 degrees down and the pinion 7 down, so way to much.   Then I added a 3 degree shim.  So trans 4 down, shaft 2 down and pinion 1 down.  And still vibrates.  That's a 4 degrees difference in angle but I read that was OK because the leaf springs will allow the pinion to rise under acceleration.

The drive shaft was sticking out of the trans about an inch or so and I thought the new shaft was bad.  I had a new one made that's goes all the way in and made sure it was balanced. Still same problem just $220 out of my pocket.

  So today I make a 6 degree shim and that should put the pinion within 1 degree of the trans ( I didn't measure it)   and today still vibrates.  I'm at a loss, any suggestions?

[70chall440]

Well, this will be a hard one, but you seem to be taking it methodically which is good. Am I reading this right that you have adjusted both the trans and rear end? Normally, I leave the trans along in the cross member, than adjust the rear end about 3 degs down.

How about wheels/tires; any possibility there is an issue with them?

Basically comes down to

1. drive shaft not balanced
2. bad angle
3. wheels/tires
4. bad axle (maybe)

I think the problem you are having mentally is that you replaced the rear end and the drive shaft so now you are not sure which it or could be. Do you have any place that could check the shaft (other than whoever made it)? You would not be the first guy to get a bad one despite what they were told.

[74BlueFish]

I would think the driveshaft is ok.  First the shortened it.   It was a Dennys driveshaft.  then I had them put a new tube on it because it was about 3/4 inch too short and I thought that might be the vibration.  Wheels and tires are the same on the car.I put all new bearings in the rearend with new 3.55 gears.  I don't think I messed it up inside of it. 

I'll see if I can get it up on a lift, maybe I'll see something different.  I've been working on the floor with the car on blocks about 6 inches up in the air.  Maybe a bad u joint even though they are new?

If I jack it and run it with the tires in the air, can you usually see a vibration( wobble ) of what is bad?


Thanks

[70chall440]

If you run it up on stands you "might" be able to see something but it could be misleading because with the tires unloaded, they can create vibration that normally isn't there.

Lets think about this methodically; you know you have a vibration, it has to be coming from some place. The challenge obviously is trying to find it, you know its there but it is being illusive. The vibration is coming from something rotating (obviously); start at the most likely and then go down the line. Any drive line vibration causes me to look at the U joints automatically as a starting point, then wheels/tires, then axles. Since the wheel/tire combo is unchanged, you can probably discount them.

Here's a question, are you sure you have the right U joints; seems pretty intuitive but thought Id ask. How about a bad pinion bearing?

[74BlueFish]

I don't think it can be a pinion bearing.  I installed new.
I'll check the u-joints.  Maybe the people who made the driveshaft, messed up a cap or lost some needle bearings. AndI'll check the part number.

Thanks

[74BlueFish]

I fixed this a while ago but didn't get back here to post this.  As I posted before, I got the driveshaft balanced 3 times, put shims to change the angles ect.
I took the driveshaft to a different shop and they found the forward universal was missing the grease seals.  I couldn't see that, nor there was any play i could feel.   They have to remove the front yoke to balance the shaft and messed it up.   The new shop replaced both universals to be safe and my vibration is now gone.  It is just unbelievable that you can bring some thing to a shop to be checked 3 times and they can't find the problem,  It's just a driveshaft.

['Cuda Hunter]

Some mechanics just don't get it.  Glad you found your problem.

[70chall440]

Its always something small