Driveline Vibration. Need HELP!

I installed 3 degree shims to fix my driveshaft vibration but am still getting a vibration between take off and 10 mph. Before install my vibration was till 30 mph so it did help some. I have my measurements taken with a angle finder.

Zeroed angle finder on output shaft
First shaft angle 5.9
Second shaft angle 5.8
Re zeroed tool on second shaft
Pinion angle .06

Any advise where to go from here?

 

This might help? At least to understand why?

https://www.youtube.com/watch?v=gmV4qwLfOMY

 

you could try a carrier baring drop

 

I dropped the cb with washers and raised the cb by flipping it. Nothing is helping. I think I have the wrong shim installed. I'm just a little confused on the correct size with the numbers I have.

 

This helped me


http://youtu.be/f1m-Fh5kiRU

 

OZ,

So after watching that video all my angles are within spec except my output shaft to the propeller shaft angle and it's about 5 degrees off. Any ideas how to change my output shaft angle?

Maybe I need to just forget the cb shims and pinion shims I have and change everything to the degree of the output?

 

So I was messing around with the angles some more and I was able to make the rear u joint angle .4 degree and the middle u joint .4 degree, according to the video and what I have read that is ideal. BUT.. My output shaft u-joint angle is still roughly 4 degrees. I don't know of any way to get this angle close to zero.

 

Probably not the answer you are looking for, but.....traction bars? Not the "right" way to fix it, but they do work.

 

Not exactly but thank you.

I'm curious what angle everyone elses output is at. No need to buy a inclinometer, you can get a free app on your phone.

 

I recently installed an OME lift with a 2" AAL in the rear. Prior to the lift I had pretty noticeable vibes upon low end fast acceleration off a stop. After the lift, acceleration vibes are gone, but get vibes at low speeds especially as I approach 10 mph while braking. I'm fairly certain this is all due to the pinion angle. All I did to correct the angles after lift was a carrier bearing drop. I could probably use a 2 degree shim as well and that would eliminate vibes I'm pretty sure. I think the key is to optimize the pinion angle relative to the second drive shaft. Not enough angle, you will have low speed/ deceleration vibes. Too much angle, you will acceleration vibes. Of course the extremes either way will have constant vibes. The diagram shows the axle wrap I was experiencing prior to the lift. When theres alot of torque going to the wheels, the axle wants to "wrap up" in the leaf springs and causes bad U-Joint angles between the pinion and second shaft. I think my problem now is just the opposite because the angle is too small. Hope this helps. If I ever get around to trying out shims, I will let you know.

 

I just noticed that based on your angles, it looks like the pinion and second shaft are nearly in-line with each other...if I'm understanding that right. I wouldn't think that's good, since you want to be able to compensate for a small amount of axle wrap. A smaller shim and might fix your problem. You can always put a gopro or something down there while you drive around, and see if you can identify anything from that. Are you running an AAL, or what?
https://www.youtube.com/watch?v=54_6GaYJvWI

 

Right now I have in a 4 leaf TSB with icon 3 leaf and I kept in the overload leaf.

 

You are correct my secondary and rear diff are .06 degrees off from each other. Watching that video oz posted it wants angles very close to each other but not zero.
I have also read on a thread that the output shaft angle and rear diff angle should be the same and adjust carrier from there. My rear diff is at 6.2 degrees right now so I would think if I removed the 3 degree shim my angles would be close since my outtput angle is about 3.2
The only thing is I messed with the cb angle down before I did the shim but didn't know I can flip the cb UP the get different angles.

 

Right now my secondary shaft and rear diff are about 5 degrees from one another. I think if I did a 2 degree shim it would fix vibrations. Interestingly though, if I put the truck in neutral, I dont get vibes where I used to. Probably has something to do with what's being explained in that video. Either way, I would think that you would want to have 3-4 degrees between the rear diff and the secondary shaft.

 

Hmmm, I would keep in mind that when you accelerate your pinion is going to cant itself downward thus decreasing its upward tilt. 0-10 mph is 1st gear range which is heavy on torque, do you have the vibes when decelerating through that speed range in neutral? It is possible you may need to decrease/increase your pinion angle to account for what is colloquially known as axle wrap.

 

Sub'd

 

I'm pretty sure its the other way around. When you are on the brakes the pinion will want to rotate down. When you are accelerating, the pinion will want to rotate up. Think about the direction of torque to the wheels...the axle will be reacting that torque and want to rotate the opposite direction. Same concept as a wheelie.

 

The video that OZ posted is basically saying that the angle between the first and second should be the same as between the second and pinion, in order to cancel out U-joint accel and decel, while keeping the angle between the output and first shaft less than 1/2 degree because there is not mating U-joint to cancel it out. If the U-joint is working at 0 degrees, there will be no accel and decel. It will operate as a straight shaft. This might explain why I'm having vibes, because I put a carrier bearing drop which increased the angle between the output and first shaft. I'm going to take it out and see what happens.

 

I also noticed that the pinion angle he measured in this video was positive 2.8 degrees, where the second shaft angle was a negative 1.8. His math was 2.8-1.8=1 The correct math is 2.8-(-1.8)=4.6. Just wanted to point that out. Its clearly more than a 1 degree difference between the pinion and second shaft.

 

You're correct, that is my bad. Good catch