Lairxj

I am curious to know if anyone else has had this rear driveline vibration as I will describe as follows: I have a 2001 Jeep Cherokee Sport with an OEM 6 cylinder Engine and Automatic Transmission. This Cherokee has been lifted approximately raised 3 inches. The rear lift is a Rubicon Express spring pack that are stiffer than stock. The front lift is also a Rubicon Express lift consisting of longer and medium stiff coil springs. My original Chrysler Rear Axle was replaced with a completely rebuilt Dana 44 out of a 1989 Cherokee. I should mention that I also converted the rear drum brakes with rotors from a 1996 Grand Cherokee. The front and rear axles have 3.73 Ring and Pinion. My Tire size is 235r75x15. I drove this Cherokee was 3 years without any vibration or noise issues as described above. I should also note that my rear driveshaft was the stock type with slip yoke. And yes, my driveshaft u-joints were replaced a few times. I also has 2.5 degree spring perch shims in place. My vibration problem revealed itself after I installed an Alloy USA Slip Yoke Eliminator and installed a modified (lengthened) front driveshaft I purchased used on eBay. A local reputable driveline company performed the driveshaft lengthening and balancing. New u-joints were installed at the same type. The U-joints were the type that are lubricated via grease zerk. With the SYE Kit in place, the Cherokee's rear pinion was rotated so if pointed to the transfer case yoke or slightly below as is the custom in most instructions. In my case the rear pinion needed 9 degree shims to accomplish this which bothered me because I was told by the Rubicon Express Tech guys that they never needed more than 4 degree shims regardless of the lift amount with their SYE Kit. They also indicated that the later model Cherokees had engines with more torque which placed more load and movement of the rear driveshaft. We tried different shims with less angle and did not see any significant improvement. We removed the rear driveshaft to return it to the driveline company to recheck the balance. It was off a little. The shaft was reinstalled. No improvement. It was at this point that I decided to order a new custom driveshaft from Tom Woods. This new driveshaft had six inches of splines versus the stock three inches of spline. The Tom Woods driveshaft was installed. There was no real reduction in vibration while under load. The vibration has consistently begun at approximately 50 mph and becomes unbearable at 70mph. Placing the auto transmission in neutral and coasting immediately stops the vibration. My auto service company doing this work gathered all 11 technicians around my Cherokee to brainstorm possible problems. It was concluded that possibly the Alloy USA yoke that came in the SYE kit may be machined incorrectly (not concentric or symmetrical) just enough to be out of balance. The double Cardan forward end of the driveshaft connects to this yoke. I contacted Alloy USA about this and they promptly sent me a new yoke. Once installed the same vibration occurs at the 50 mph speed. My next step is to take the new yoke to a machine shop,to have a full dimensional check of the part to see if it is truly concentric and symmetrical. My is hoped we find this yoke to be the culprit because we have run out of new ideas? I hope someone out there has faced this problem before as I have described above.

Randy In Wichita

Octavius

Mine does it to under any acceleration, the dash starts shaking like crazy, all my change jumps up and down.

Demonoid369

My thoughts are have you checked mounts? Check the bearings? Chain, exhaust? Did the d44 get rebuilt correct?

Lairxj

All mounts are in good condition. The D44 was rebuilt 3 years ago and has be quiet and worked fine prior to the SYE Kit mod.

Your inputs are appreciated.