I have been chasing a vibration for awhile now, I have narrowed it down to the rear. After taking a angle finder to the drive shaft and pinion, I have noticed that the pinion angle is below the drive shaft by 4 degrees ( I am using a 6 degree shim). Is this enough deviation to cause a vibration above 60 mph were the vibes start?

I have swapped the drive shafts around, both have been balanced and fully rebuilt, cant see it being the drive shafts then.

 

Mine is close enough to not bother with it. I get a small vibration at 60ish.

 

Yeah just seems kinda odd, its all smooth then just starts out of nowhere. Id like to be able to fix these vibes.

 

The short answer is yes, it could be the reason for your vibration but tough to say for sure without knowing more....

 

I'm going to take it for a drive later today with just the front drive shaft in, just be sure it is the rear. I have the front out right now and its the same vibes still. I used a advance adapters SYE if anyone wanted to know.

 

Are you talking about the yoke near the diff, or the yoke off of the TC?
If you are talking the one near the diff, it needs to be as straight to 0* as possible. Kinda like this:



The one on the bottom is how it should look, you need to be as close to 0* as possible. The double cardan joint at the top is where all the angle happens.

 

Typically you want your angles between 1-3 degrees. Anything more will normally lead to vibrations. If your angles are within that range, then check to see if the yokes are clocked properly.

 

Clocked properly?

 

The yoke at the differential side is 4 degrees lower then driveshaft angle. The t case side does it have to be 90 degrees like that? Mine is tilted downwards even with a new transmission mount.

 

It can be pretty persnickety. I used 4* shims when I installed an SYE on my RE 4.5 lift, the angles were pretty close but I still got vibes. Later when I swapped the rear axle, I put in 6* shims and the problem went away.

 

I am running the RE 3.5" leaf springs, with a JKS boomerang shackle, 6 degree shim atm. Im probably near 5" lift in the rear considering the 3.5 springs give more lift than advertised. I may try out a 8 degree shim, IRO makes one and so does RE.

 

It's just a sample pic to show the angle difference. Top pic shows a theoretical example of 15*, bottom pic shows the cardan joint splits it into 2 angles of 7.5* each.

You need to degree shim the diff side to get to within 1-3 degrees of 0. The closer to 0* the better. Try using a 3* shim instead of 6*, it will depend on which direction it's off. You might need to add a 3* shim, you might need to remove a 3* shim. Hard to tell without pics. Jockey the shims around until you get the bottom as close to 0* as you can.

 

Well I have a 6 degree right now so Im going to try an 8 degree itll bring it within 2-3 degrees then.

 

There ya go. Keep us posted on the result.

 

Will do, I have some aluminum shims that are for spring under, going to machine them down to 8 degrees for temporary use until the steel ones get here.