driveshaft problems

I have a 75 cj5 w/ a 258, t-14, d-20, d-44 axle and my rear driveshaft angle is outrageous. I put a 2.5" lift on it and with the t-case lowered .75" I still have a 22 degree angle. I calculated it with the stock springs and it still comes out to be 14 degrees. The driveshaft also runs a compound angle(both left to right and up to down), being 3 degrees out of alignment with the transfer case to pinion side to side.
I did not shim the axle yet to take these measurements, however, the axle and t-case yokes are even at 85 degrees(with the case lowered .75") If I shim the axle these angles will be different causing uncancelled vibration. I know I should probably use a cv shaft but I am concered that something else is incorrect and do not want to spend a ton of money before I can correct the original problem.
Does anyone know the original rear driveshaft angle of a cj5, and a pic of the stock trans crossmember(for the 258 engine), or pics of a 75 with no body on it. I would greatly appreciate all the help I can get. Thanks, Robert

 

Do you have a vibration from the driveshaft? I have a 4" lift, a fairly short driveshaft and I'm using 4 deg shims to point the pinion up a little. My driveshaft is a CV and I don't have any vibration. Also, I've dropped my t-case about 1".

 

I'm fairly sure. I removed the rear shaft and put it in 4wh and it drives fine. When I drove it in rear wheel drive I could not get over about 15mph without it feeling like something was about to break. I made some test shims and got the shaft angle to 14 degrees, it ran to low 3rd(about 25 or 30mph) then began to vibrate badly. What is your driveshaft angle? I've read the shaft can sometimes be out of phase, but do you think that this is a possible fix with the angle being so extreme?

 

Have you changed tires? Knew a guy who had tons of vibration...one of his tires had its weights fall off whilst sitting in the garage. Balanced the tires and the problem went away.

 

So did you check the shaft to see if it is out of phase? Out of phase will give you some knarly vibrations up till the point it brakes.... just set the shaft on a level surface and make sure the joints are pointed the same way. My shaft is at a huge angle also, never measured it tho. I don't have any vibrations. On green jeep with the wrangler springs I am going to have to go to a CV shaft as the joint bottoms out in the yoke and binds at full suspension travel.

 

i have the same problem. installed a 4" pro comp lift with a 1/2" lift shackels and my rear driveshaft is at a crazy angle with a 2 degree shim. drove at about 10mph and my entire drivetrain almost snapped. got under it and seen the u joints are binding in the yoke. called drivetrain specialist and they said a 6 degreeshim should cure my problem suppose to here in a day or two. will let you know if that will correct it or not.

 

A driveshaft gets out of phase when the slip yoke either falls off or is removed and gets put back together improperly. Sometimes there is an arrow on the driveshaft or on the slip yoke that aligns with a mark on the shaft or yoke. If there is no mark, it must be assembled so that all the u-joints are facing exactly the same direction.

 

Thanks for the help. I just checked the shaft and it was far out of phase. I Just aligned the arrow to the mark and will install on the jeep tonight. I am keeping my fingers crossed. I will post a reply after I drive it and see what happens. Thanks Rob

 

I installed the shaft and it drove perfect, not a hint of vibration!!!! This has been a 2 year project and I've only driven the jeep about 5 or 6 times, just to test it and initially break in the engine; this is how I found out about the super vibration; I had to drive it in fwd which is quite difficult on the street. I've rebuilt the engine completly, sandblasted and coated the frame with por15, new brakes lines, just about everything under the body is new. Now comes body restoration, but at least it drive great. Thanks for all the help everyone. Robert

 

And also, if you still get a vibration, rotate the yoke 180 degrees (half turn) Drive shafts are ballanced with the yoke assembled to the shaft.