4" lift on 74 CJ5 vibrations now

4" suspension lift on my 74 Cj5. Shimmed the rear axle, 1" transfer case drop, and CV joint on rear driveline and I still have a bad vibration with acceleration and deceleration. Help. Everyone I ask says the same thing.. did you do all of the things I said above... and I say yes and they say Ohh I dont know what else to do. I also checked my engine mounts and they are solid. Any suggestions?

Brian

 

ck u-joints are they all new? also make sure your drive line anges are with in opperating spec. for the u-joint or cv joint. may be axel rap is causing excesive angles. other then that I am out of ideas with out seeing the jeep.

 

What kind of lift, spring over? They axle wrap pretty bad. Might be your springs are just softer allowing the axle to wrap(twist). With the cv joint your yoke on the rear end should point pretty close to straight at the transfer case. I did this and no vibration, but also only a 2.5 lift with long shackles.
Also check to see if your driveline is in time, the yokes need to be the same at each end of the drive line while rotating, if it is wrong, just pull it apart at the splines to re-time if it is wrong. If I am not making sense, look at my picture, both ends of the driveline are positioned the same and the ujoints will break over at the same time. I'm not always the greatest at explaining these things, good luck, should be fixable.

 

What GPin said. Phase is the word. The caps of the U joints should line up. The pinion pointing at the transfer case is my guess tho. If you didn't cut the perches off the axles and rotate the pinion that is what you need to do. With a rear CV joint shaft I would think you could loose the axle shims, loose the transfer case drop, rotate the pinion up and be done with it? Anyone else?

 

Thanks GPin and Jeep Therapy... I found the problem. I need to rotate my rear diff up to put it inline with the driveline. Whats the easiest way to do that? Just cut off the mounts on the axle and re-weld at the correct angle? Does that cause any other problems? Thanks again.
-B

 

I have shimms already in place... how steep can I go on the shimms. And it is a brand new lift with new U Bolts

 

I think to rotate your axle that far and for a permanent fix that you seem to be going for, I would cut the perches off, rotate your axle and weld them back on. The shims, at least with my experience with aluminum shims, crack and want to work around if you tried to stack them. I have not had any problems reusing a u-bolt.

 

I agree with GPin, I wouldn't run shims either. I have also often seen them crack. I also wouldn,t drop the t-case unless I had to. That defeats the whole purpose of running a double cardan joint like you are. Another thing; When you rotate your pinion up, leave it shy a couple degrees of being straight because when you put the rear under load, the pinion will rotate up slightly. I also agree with GPin on the u-bolts; I have re-used them plenty of times.

 

I should have mentioned that I also ran my pinion pointed slightly down from straight, good call cj-x. Mine is nice and smoooth!

 

X2 too!

 

thanks everyone for the input. Picked up new perches today and will weld tomorrow. thanks CJ-X...i will make the angle just shy of even. Oh and I am definately taking out the t-case drop kit. I will put up some before and after pics in the next couple of weeks... ALMOST DONE.. excited. Been a year in the making. Thanks again.

Brian

 

I have a skyjacker 4" lift in my 73 CJ5, came with 6 degree shims. Used a custom CV drive shaft and differant yoke output for my dana 20,also note;6cyl,dana18 trans. No vibations. Pinion has to point at or just below center of CV joint,slightly below because axle rotation under load.

 

when you rotate your pinion to point up to the transfer output, remember that the fill hole on the diff cover is lowered slightly in relation to the gear set inside the pumpkin. Best case scenario, overfill. Worst case, move the fill plug up on the diff cover.

 

As a rule you shouldn't go more than 7 degrees or so, anything much more than that will cause a reduction of lube to your pinion bearings. Try the shims, if they work out then later you can cut off & re-weld the spring perches, I don't like cutting & welding till I'm sure it is the proper way to fix the problem.

With a cv at the rear of the T/C I'm surprised you are still having problems. I am running a rear cv shaft with no t/c drop and only 4 degrees of rotation to the yolk angle and have never had any vibrations.

 

A good thing to do is get a differential cover from a high pinion dana 44. The fill hole is up higher. Worked out just perfect on mine. They are easy to find also; common on the front axle on older ford pick-ups. As a bonus they are made of heavier steel.

 

:iagree:
Quality steel shims are inexpensive and simple to install. The simple approach first. It sounds like a large number of knowledgable individuals use the shims w/o problem. JMHO...

 

Make sure if you are going to run a thick shim that your center pin in your spring is long enough to still engage into your axle perch.
I was out wheeling once and drove into a ditch and broke a front spring center pin and shoved my tire back into my fender, that was probably a rusty stock center pin, but too short of pin will have the same effect.