I have a 2001 Cherokee with 3.5" Rubicon Express lift, 32" tires, 4.56 gears, aftermarket control arms, SYE kit and cv driveshaft, axel shims.

Before the SYE kit and axel shims, it had a bad vibration from the drivetrain at almost any speed. With SYW and shims it is smooth as glass through aroung 67 MPH. At around 70 MPH, a vibration appears like flipping a switch. The vibration is worse if I am on the throttle, but it is still there even if I take my foot off the throttle, as long as the speed is above 70.

It is an almost resonant vibration, it sounds like it could be tire noise, but it really comes and goes like flipping a switch at around 70 MPH.

What could it be?

 

i just rebuilt my front driveshaft and am now experiencing the exact same thing, right around 65 mph. when i had it off it was smooth as butter all the way to 83, which was never able to be done before

have been searching and kind of sounds like an out of balance driveshaft so im picking up a used one at the junkyard tomorrow to see if it helps/hurts at all, will update when i find out

 

Sounds like your new CV driveshafts need to be re-balanced. If it was anything else it would vibrate all the time but, only above 70. I'd say DS balancing issue.

 

its a jeep.

 

Is there any way to check the driveshaft, or do I get it balanced and see if that fixes it?

 

That's not an excuse for it to run poorly. Any problem can be fixed if it can be diagnosed.

 

Sorry, bud. Really no way I know of a backyard mechanic to check a driveshaft for proper balancing. If you want it done right, you need to take it into a driveline shop and have them spin and balance it on there high rpm spin balancer.

 

Mine was like that recently as well except was was exactly 50 mph, It would go from my normal vibrtaion to shaking me to death just like that right at 50 mph, Mine was actually 1 tire on the back had a seperated tread.

 

definitely have it balanced and whenever you take it out mark it so it goes back in the same way also check your ujoints

 

i had the same exact problem. at first i discovered a bad U-joint that connects to the rear diff. fixed that, still having the vibration. so i pull the whole drive shaft, find i have a bad tranny mount. fix that, vibration still their. at this point i did something i don't recomend,i put the car on jack stands and drove it to see where the vibration iwas coming from. i found the vibration and noise was coming from my slip yoke eliminator. pulled the whole drive shaft and took it in to drive line, in denver. Jeff was able to rebuild my old drive shaft and balance it for super cheap. that fixed my problem, it was such a relief to get that problem taken care of.
i would recomend these guys if your having drive line problems, and live in the Denver metro area. great service, friendly and a lot of knowledge.
PM me if you need their contact info. hope you can get yours fixed to.