First I put the lift kit (4" superlift kit) on the front end of my 83 CJ7 and drove it till the next weekend when I put the rear half on. Everything was fine with only the front on. Now, with the rear on I get a vibration from the drive shaft it seems at around 40 and up. The when I let off the gas I hear a noise like a 10 speed bike would make when you are coasting only heavier, click click click click.... etc.
The kit came with a transfer case drop kit but I didn't install it. Others I have talked to said they didn't use the transfer case drop kit.
Has anyone else had this problem or can anyone give a comment or help?
I had exactly the same problem. Only I didnot know where to put them 6 large shims I got left..... After I dropped the transfer case with those Shims, the problem was gone.
There is another solution to that problem, the Slip Yoke Eliminator Kit. It helps to give you ground clearence, but it will cost you an arm and a leg.
Install the T-case drop kit. All vehicles are a little diiferent from each other. The install should stop the vibration. Or, at least minimize it. If vibration still exists, you can tune the rear axle shims to completely eliminate the vibration.
The clicking you hear is the sound of your driveshaft ujoints. They have worn in at a particular angle and are now running at a greater angle. Be sure they are freshly lubed. The clicking may go away as the joints wear at the new angle, however they are likely to fail at the most inopportune moment. If I were you, I would replace them.
The vibrations at 40 mph are caused by the now incorrect driveline angle. Install the transfer case drop.
Do the SYE (slip yoke eliminator) kit and put on a CV driveshaft. Anything 4" and higher, the t-case drop kit is likely not going to get rid of ALL the vibrations, and you'll be wearing down u-joints at an accelerated rate (not to mention, if that axle drops fully off-road, those u-joints will be likely to snap). It is somewhat expensive (~$500 parts), but if you installed your own lift kit, you definitely have the skills necessary to complete this task (it's not that hard...I did it! lol), so you can avoid the additional ~$500 in labor. And, as another poster stated, once you get the CV shaft in, you'll have to shim your rear axle then, to point the pinion straight toward the CV joint of the driveshaft at the t-case output flange location.
You can probably wait a year or so at least to do this, though, if you want. I did. I just waited until the vibration in my rear driveshaft got really bad from the high operating angles eating the u-joints, then finally broke in and plunked down the dough to do the SYE and CV driveshaft. Just be glad you don't also have to buy adjustable control arms to aim your pinion ($250 more for me!)
BTW, I would have loved to see what that looked like, you driving around with your front end lifted 4" and your rear at stock height. Must've been an amusing site. Not to mention interesting to drive... ;-)
Actually, I didn't really realize it at the time but I had 2.5 " lift springs on there from the previous owner. I'm running 32" tires. It wasn't too bad, just leaned back a bit.
Vibrations are typically caused because of mismatched angles (I was told)
I solved that problem when I was doing a T18/Dana300 - T150/dana20 swap.
I used thicker motor mounts so the engine/tranny/transfercase pointed downwards a bit more. I had to have a custom made skidplate/crossmember because of the new driveline. What I did is, make sure that the imaginary line of the outputshaft of the tranfercase and the imaginary line "straight out" of the rear differential are close to parallel.
When that's the case then there's (almost) no difference in angle of the u-joint near the transfercase and u-joint near the rear differential. when that is done the u-joints cancel out each others vibrations. The angle the u-joint has to overcome might "still" be larger then "spec" but not having noticable vibrations keeps the u-joints and other parts alive longer then having the same driveline angle problems WITH vibrations. The guy in a shop that build my new driveshafts for after the conversion told me that (and showed me).
According to him u-joints are supposed to operate between certain angles, but (according to him) it is really important that the front and rear ujoints have the same angle. He told me that the vibrations are caused by [1] driveline angles that are too big. [2] teh difference in driveline angle between the rear and front should be 180 degrees so that vibrations can cancle each other out. Also ... get real good u-joints.
I listened to his advice and my just over 1ft rear driveshaft that has a pretty steep "angle" never caused any notible vibrations etc with my 4" lift. As for the front driveshaft, yes the angles are mismatched there, but within the specs of the ujoints (rear driveshaft got real short, front driveshaft got real long) besides I almost never drive "fast" in 4wd anyway.
Ron
btw: a CJ7 is about 12" l> BTW, I would have loved to see what that looked like, you driving
Well vibration is a frequency thing. So it might get worse and better at different speeds. Things that vibrate have an "eigen frequency" that makes them vibrate/move pretty violant at certain frequencies.
Check the driveshaft for missing balancing weights. (or have a driveline shop balance your driveshaft)
isn't the driveshaft hitting anything ?
R> If the clicking were the U-Joints, wouldn't I hear it all the time and not
Actually, now that I think about it, I need a new tranny mount. Perhaps that, along with the Transfer Case Drop kit will do the job. I'll get it done tonight and we'll see.
You need to drop the tcase with the shims, or get a double-cardan driveshaft. If you already have a double cardan (CV) driveshaft, then you have broken the ball thingie in the center. A double cardan has two Ujoints at the tcase end, and in between these two ujoints is another part that is basically a balljoint with a small but heavy spring inside. The spring acts to keep the two ujoints lined up, but if the ball portion of this joint breaks, then the ujoints can flop around relative to each other, and this will set up the vibrations you are talking about.
One other thing you might need is to install those wedge-shaped shims between the axle and the springs. This will tilt the pumpkin up a few degrees and make the angles of the driveshaft a little flatter.
I just spoke to the place I bought the kit and they told me the shims that are on the rear springs are designed to be used in conjuction with the transfer case drop kit, they create an angle that will expecting the transfer case drop kit, and that the transfer case drop kit is a critical piece of the kit. When this is installed it should take all vibration out or if there's any it will be very minimal.
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