How to determine shim angle

[Polaris]

I am putting in a 4" spring lift and wonder if any of you know what degree of shims I should get? Thanks!

 

[Mr.Chevy4x4]

If you are going with rear springs they will more than likely have a "built in" shim. You need to make sure that after the lift that both of your u-joints are working at the same angle to prevent vibration. You might want to drop your transfer case with the spacers that are currently on top of the lower frame rail. Just put them between the frame and the crossmember for about 1 inch drop. This should help some also.

Or, you could call Jesse at High Angle and get him to make you a CV shaft and not worry about it! /forums/images/icons/grin.gif /forums/images/icons/grin.gif

Mike

 

[ftn96]

My Skyjacker 4" rear spring lift came with a 4 degree shim. Still had to lower the T-case. Then I woke up and called Jesse and got my CV 1ton shaft. /forums/images/icons/grin.gif

 

[trukman1]

Driveshaft to yoke angles should only vary 2-3 degrees between each end with 4 degrees being the maximum.

 

[OneInTheSun]

I'm almost positive Superlift's come with a 3 degree. Even with those shims and the transfer case drop, I still have a bit of vibration. From my half-assed calculations, I figure I need a few more degrees of shim. When I get around to putting the ORD 1" add-a-leaf in, I'll probably replace the 3 degree with a 6. (I'm just guessing on the 6 degree - anyone have a similar situation/definitive answer so I don't have to trial-and-error it?)

 

[ftn96]

Go to home depot's tool department. Go to the levels and pick up the round level, AKA angle finder. Buy it, go home and measure some angle to correct way. It's to easy and cheap and more accurate than most other ways floating around this world. /forums/images/icons/wink.gif
#1 Measure angle of the driveshaft, somewhere ball park say of 20 degress. Then remove the driveshaft, place the finder on the flats of the pinion yoke. Subtract that ange from the D-shaft angle...Then repeat based of the rear output housing of the T-case. Those are the 2 angles to compare. If they fall outside of the recommended 2 Degrees, then you have to judge how exceptable that limit is for your personal preference.
May the masters of Geometry and Physics be with you. /forums/images/icons/wink.gif /forums/images/icons/cool.gif

 

[ftn96]

Oh, one more thing!! Need to check to make sure your driveshaft is long enough. IF it is too short it will tend to vibrate a little, and more so if it (assuming slip yoke style) if the spline are worn out, which often has other side effects ontop of risking driveline seperation. /forums/images/icons/ooo.gif

They are (if that is your problem) not that expensive, bout $80 bucks, I think. Don't put off till tomorrow what you can do today! Like drink beer....? /forums/images/icons/grin.gif /forums/images/icons/tongue.gif /forums/images/icons/wink.gif /forums/images/icons/cool.gif

 

[OneInTheSun]

Good advice. I actually did use an angle finder (borrowed a top-notch digital one). I just wanted to see if anyone else has the same setup/situation. I want to put the shims in at the same time as the add-a-leaf and get it over with all at once. I've got a good idea of what I need, just thought someone might have the definitive answer.
One more question: I know the pinion, at rest, should be 2 degrees off of "center" to eliminate axle wrap. Does that mean two degrees down or up?

 

[ftn96]

2 Degree Down, as the wrap will make the (front of the)pinion will want to rotate upwards. Thus 2 Degree Down. /forums/images/icons/cool.gif