radicalvette

I did the front drive shaft swap I read so much about out of a 93 ZJ with the V-8 measured 33 "... now I can't get rid of a highway vibration. I have check the phase alignment on the drive shaft and all the u-joints are in line and I called Rough Country today whom I purchased my x series 4" lift from and discussed removing the 1" transfer case drop to bring the front yoke back to level as it had a slight upward angle with the T.C. drop and they said to remove it. I removed the T.C. drop and had some improvement but still unable to run over 62 mph on the interstate with out getting to much vibration. Im thinking my next move is to spend 50.00 to have the drive shaft balanced and if that checks out I guess a frt pinion angle adjustment to bring it to near 0 degrees with the lower u joint slope but thats going to entail degreed ball joint installation and adjustable upper control arms im thinking wow I had no vibration with the old style C.V. joint drive shaft.

radicalvette

So if the pinion has to be near or at 0 degrees with the pinion u joint there is really no other way but to adjust pinion angle that I see without adjustable upper control arms. I don't want to adjust my lower arms as that would bring the tire in closer to the body and with 31s they still touch every now and then. Tell me what you think ? Thanks

dave1123

The CV on the front end acts like a double-cardan joint and the only way I can see to fix this is to put a double-cardan on BOTH ends or use a single joint on both ends.

The thing with a u-joint is the driven shaft accelerates and decelerates every 1/2 revolution when the drive angle is anything but straight. The greater the angle, the greater the speed change. This is why the u-joints get pounded out on high angle drives. The double-carden joint was invented to take care of this shaft velocity change problem and works well at doing so, however at higher torque levels has limited life. The CV joint was invented to solve BOTH the angle and torque problems.

Another thing working here is spline length. The more angle there is in the drive, the more the shaft length changes when the axle moves up and down. CV joints used on the axles of front wheel drive cars have longer internal splines than the ones used on your shaft, so the mid-section splines need to be longer. I think there was one setup on a jeep that had CV joints on both ends of the front drive shaft.

The only way I can see of pitching the pinion up without changing the spindle angle requires cutting the welds at the tubes and rotating the carrier assembly. This will require jig&fixture work it get it right. Not something easily done.

radicalvette

Im going to check the balance on the shaft. Looks like for now as much highway driving as I do im going to have to lay the shaft in the back incase I need it lol. I need to check and see what the factory pinion angle was before I installed this lift and see just how far I can push that envelope on pinion angle verses caster and make sure im atleast at factory pinion angle. I'll go by today and grab a angle finder.

radicalvette

I have about 7 degrees + slope on the transfer case output yoke and 5 degrees + on the frt. Pinion yoke with a 9 degree slope angle on the front shaft.

dave1123

Okay, the factory caster angle is 7* + or- 1/2* so the front shaft isn't that bad. I guess it just looks bad with the wheels hanging on the air.

radicalvette

The drive shaft shop said I need to be at 0 degrees no more than 2 degrees at the transfer case yoke and that would take care of my vibration so I told him all I could do there is shim the transmission mount upward in the rear he said that would be fine. I guess ill try that this evening an go from there. Were talking about a difference of 5 degrees to compensate for thats not that much but he said the double cardan joint had to be level or like I said within 2 degrees.

radicalvette

Scrap that idea thats b/s... im ordering adjustable uppers and add a degree or 2 and work it out at the pinion !!! That's the only consistent answer I get from Rough Country as well. Everybody else I called doesn't have a clue and I spend more time educating them ... sometimes you just have to fineese it and see what works and doesn't work lol

radicalvette

I am seriously thinking long arm upgrade at this point. Not sure I want to throw money at adjustable arms when I can complete the long arm set up for not much more money if I start looking at adjustable arms for the rear and upgrading the tri link bar. I may order it this week

radicalvette

Added front adjustable arms and set my pinion at 7 degrees no help.... the drive shaft was bent so I had it retubed and shortened a 1/2 so I could pull the drive shaft on the lift at full drop. I had all 3 u joints replaced and centering ball on the double cardon joint and re installed. I can run 70 mph on the interstate now and vibration free

dave1123

Duh! Bent Shaft! Why didn't we think about that before? Makes a lot of sense.