CJ-7 Strange Vibration

[Rescue Diver]

well this may sound dumb but do you have new hub lockouts? I had a very similar vibration after i replaced mine with new ones, but i just ran it and it quit after bout 3 or 4 months.

At first I actually wondered about that. With a small amount of play in the front drive shaft slip joint, it made me think maybe it might be turning and vibrating because one of the lockouts was catching once in a while. I removed the front drive shaft and drove it a few days, but it didn't make any difference. I've since taken the hubs apart, cleaned and greased them. I'm pretty sure the vibration is coming from somewhere in the area from the Transfer Case to the rear axle.

My 6 degree axle shims finally shipped out and are scheduled for delivery today. I'll install them tonight and hopefully know if it fixed it after putting some miles on it. It's really annoying! It'll be totally smooth all day, and then it'll just start vibrating a little when I hit a small bump in the road. Then after coming to a complete stop and starting out again, it's smooth again.

I originally started this thread expecting someone to say, "Oh yeah, that's a common Dana 20 or AMC20 problem." I guess that isn't the case.

 

[bdunnam]

Make sure one of your brakes isnt catching, a friend of mine has a 79 ford on 44's with disc brakes all the way around and one of them is catching, and its making a vibration almost exactly like what your talking about.

 

[dwyant30]

Have you figured it out yet? Just wondering.

 

[Rescue Diver]

Have you figured it out yet? Just wondering.

I installed the 6 degree shims between the axle and springs and it still did it off and on the first couple days, but then it stopped and hasn't done it again. I'm confused. I keep thinking it has to be an issue with the output shaft bearing on the Transfer Case , or the axle pinion bearing. But again, I have no idea why it would come and go like it does? Whatever it is, I just wish the damn thing would fail hard so I can figure out what's causing it!

 

[Rescue Diver]

Make sure one of your brakes isnt catching, a friend of mine has a 79 ford on 44's with disc brakes all the way around and one of them is catching, and its making a vibration almost exactly like what your talking about.

I thought about the brakes, but if it was that, I would think lightly applying the brakes would make it change when it's happening, but it doesn't.

 

[bdunnam]

Yea true, some other thoughts are, do you run a detroit in your rearend, they will make funny noises and i believe some vibration but its more noticable with larger tires, like 44's for example, but also check all of your yokes on the jeep, make sure that all the nuts that hold them on are tight, when mine was doin the same thing someone told me to check the front yoke and make sure that it was tight, apparently if they get loose itll cause them to vibrate randomly, and i wish i could remember if thats what fixed it or not

 

[Rescue Diver]

Yea true, some other thoughts are, do you run a detroit in your rearend, they will make funny noises and i believe some vibration but its more noticable with larger tires, like 44's for example, but also check all of your yokes on the jeep, make sure that all the nuts that hold them on are tight, when mine was doin the same thing someone told me to check the front yoke and make sure that it was tight, apparently if they get loose itll cause them to vibrate randomly, and i wish i could remember if thats what fixed it or not

I haven't gotten around to installing a rear locker yet. Good suggestion on the yokes. That was one of my first thoughts. I checked them originally and they're tight.

 

[bdunnam]

well i dont know then man i say just run it and forget about it, if it breaks, it breaks, but atleast then you will know what was wrong with it, and who knows it may quit

 

[Rescue Diver]

well i dont know then man i say just run it and forget about it, if it breaks, it breaks, but atleast then you will know what was wrong with it, and who knows it may quit

Yep. That's about where I am now. It decided to do it again yesterday after work a couple times, but didn't do it on my way in this morning. It's much less noticable since I lowered the cross member and installed the axle shims to reduce drive shaft angle. It has to be related in some way to that section of the drive train. Guess I'll wait for it to fail hard like you said.

Thanks everyone for all the suggestions!

 

[Az84cj7]

Hey Rescue Diver. I just read your post. My 84 is doing the exact same thing you have explained. It is annoying the hell out of me. Did you ever figure out exactly what it is. You described it to a T. Thanks for your help

 

[ThisGuyUKnow]

hey rescue this may sound stupid but check your tire tread wear. My roomate was having a similar intermittent vibration that would shake the hell out out of her whole car (ok it was a tiberan but still) on the road. I drove it and couldn't even come up with the foggiest idea of what it was. Turns out one of the tires was extremely un evenly worn out.... When she told me that is what the shop did (replace one tire) I was like BS I didnt believe it. I thought they just made something up jut to make a buck but sure enough it went away.

 

[Rescue Diver]

Hey Rescue Diver. I just read your post. My 84 is doing the exact same thing you have explained. It is annoying the hell out of me. Did you ever figure out exactly what it is. You described it to a T. Thanks for your help

Nope. No luck at all. It only does it once in a while and I guess it'll take a hard fail before I'm ever going to get to the bottom of it. I'll update this thread if I ever figure it out. Good luck!

 

[Az84cj7]

I dont think it has anything to do with those shims or drive shaft angles. I've been driving mine for over 5 years with a spring lift and have never had one issue until 2 weeks ago. Its so strange! Just like you said, its not a shimmy or a shake its more of a buzzing vibration coming from the drivtrain. Steering wheel doesnt even move......
Anybody else had this prob?

 

[Rescue Diver]

I dont think it has anything to do with those shims or drive shaft angles. I've been driving mine for over 5 years with a spring lift and have never had one issue until 2 weeks ago. Its so strange! Just like you said, its not a shimmy or a shake its more of a buzzing vibration coming from the drivtrain. Steering wheel doesnt even move......
Anybody else had this prob?

Good description. Does yours also seem to start doing it when you hit a small bump in the road and after a complete stop it isn't there anymore?

 

[Az84cj7]

That is exactly what it does. It seems to only do it when I hit a small bump. Sometimes is will correct itself if i accelerate or downshift but mostly have to come to a complete stop and then it goes away. Very annoying

 

[Rescue Diver]

That is exactly what it does. It seems to only do it when I hit a small bump. Sometimes is will correct itself if i accelerate or downshift but mostly have to come to a complete stop and then it goes away. Very annoying

Yep, that is exactly it. We can't be the only people experiencing this? What Transmission , Transfer Case and axles do you have???

I'm running a 1979 T-18 4 speed Transmission with 6.32 to 1 first gear, a 1979 Dana 20 Transfer Case , and AMC20 rear and Dana 30 front axles with a 4" spring lift.

 

[Az84cj7]

Cj is an 84 with The T-5 5speed. Not sure of the gearing. Dana 300 with 4.3to1 kit, Dana 44 rear and Dana 30 front with 2.5" rancho and heavy duty shackle set. 33 bfg AT.
diffrent components but exact same problem. I find it hard to beleive but maybe driveshaft???? Im puzzled

 

[Brodie14]

Any updates on this thread? Just picked up my 84 CJ, 4" lift, 350 V8 and I have the exact same vibration. Usually happens when I'm crossing a bridge, as soon as I drop off the joint, I get a vibration that you can feel in the seats. The steering wheel doesn't shake, it feels like it's from the TC on back.

Any new info?

 

[dpuck]

I had a very similar thing going on with mine. It would only do it occationally or when I hit a small bump. I could feel the vibration in my seat and floor and hear a low grumble. I replaced all driveshaft u-joints and rear axle bearings. Didn't help. So I went to the front. The locking hud on one side was gabage. figured it was trying to lock up while driving. Found the spindle bearings needed to be replaaced and the axle shaft u-joints were dust. Went ahead and replaced whell bearings and all seals while I was in there. Problem solved. Not sure which compnent was the culprit, or a combination of, but I haven't heard it in the last month since I did it. Hope that helps.

 

[Rescue Diver]

Oddly enough, I kind of just got use to it happening once in a while. Then a couple months ago my nearly new throwout bearing failed. After reainstalling the tranny with a new throwout bearing and front retainer, it hasn't done it since. I can't say for sure that it was the T.O. bearing, but it's possible.