Vibration when driving

[jay79cj7]

Tugly the Jeep Now called Wolverine!

I am looking for some ideas as to what my problem could be. First, here is my CJ: 79 CJ-7, 258, auto, quadratrac w/ part time conv, stock narrow track axles, no lift (or a very small one that the previous owner put on and I don't know about).

When I hit the gas from a complete stop, I get a vibration that seems to come from the back end. It is kind of a up-down or front-back vibration, but not side to side. The harder I accelerate, the more extreme the shake. This is also made alot more severe on the rare occassion that I have a rear passenger. Once I get going, say 15 mph, the vibrations are pretty much gone (besides the normal ones). I can accelerate as fast as I want from that speed without this vibration.

One of the leafs on my rear passenger side is cracked in the center. I am waiting for a good chance to replace it. I think the driver side is OK. It doesn't seem like this is the problem, but I thought I would mention it.

Other than that, it seems to drive very well. I can go up to 75 mph on the highway and it rides smooth.

Any suggestions?

Thanks

Jay

 

[Deerhunter30]

Sounds like wheel hop. Do the tires squeal at all?

 

[jay79cj7]

What is wheel hop? What causes it?

It does kind of feel like one wheel is bouncing or turning at a different rate than the other. The tires don't really squeal though. I think they might have sbefore I got new ones last year... they were pretty bald. I don't remember. It has been doing this for a while, and I finally decided I need to figure it out.

 

[Deerhunter30]

Wheel hop is usually when a vehicle is under load. The springs will load up and then the tires will loose a littel traction and then the springs will unlaod. Then the springs load up again and loose traction....etc....etc.

 

[Snitty]

now THIS is what I need

check your rear universals my man... my straps come loose now and then and i get EXACTLY what you are talking about

 

[jay79cj7]

What to do with Spare locked up Trans.

OK, excuse my ignorance here, but what are these straps? I assume you are talking about my U joints between the t case and the diff.

 

[jay79cj7]

Oh, and if this is wheel hop, do you think that broken spring is to blame?

 

[Snitty]

there should be either straps or small ubolts holding the universals to the yokes... if they are loose, they can cause nasty vibration... i had a broken yoke one time and the ujoint caps kept sliding out... then after i changed my transmission, the bolts kept coming out... so i had to retorque them a few times...

if it is wheel hop... it could be from a broken spring, uneven suspension can cause strange things

 

[jay79cj7]

Thanks for your help guys! This website has been my greatest find since I got my CJ. I learn a ton by reading it regularly. Anyway, I hope with this advice I can crawl under there and figure it out this weekend. I gotta fix an exhaust hanger anyway.

Jay

 

[Snitty]

well lets hope you can solve this deal

 

[jay79cj7]

OK, I crawled under there today to check out the U joints. I think I know what you mean by "straps" now. I assume they are the U shaped bolts that holds the universal joint between the yoke and driveshaft. They didn't seem loose. One thing I did notice however... on the quadratrac unit, there are 2 bolts on the transmission side that hold the tcase housing to the frame support bar. The tcase housing mounting area is broken off around one of the bolts... It just spins around freely and the tcase isn't held by it at all. Is this related to my problem, and could it cause me any other problems? (I don't do any off-roading YET.)

Oh, and on a different note, my exhaust pipe ahead of the muffler is rotating freely at one of the joints. I need to get a new clamp and tighten it down, but is there any kind of adhesive or putty or anything to seal these kinds of joints?

Thanks again.
jay

 

[olyeller]

YJ needs a new power plant Possible TJ?

check your rear axles. sounds like the axle may be spinning inside the hub. i'd check the passenger-side first. i had a similar thing happen to my cj and found that the tapered axle/hub had worn and the axle would spin without turning the hub. i finally found out what was causing the noise after i had to use the front wheels to pull me home one day.

 

[jay79cj7]

That's something I hadn't thought of. The easiest way that comes to mind to check that is to jack up the rear and hit the gas, and see if both wheels spin. Does that sound like a good method? I would prefer not to take stuff apart if I don't have to... I don't have a garage to work in.

Thanks,
Jay

 

[TwistedCU]

If your transfer case is loose it will without a doubt cause vibration, and eventually more problems (starting with the universal joints).

 

[olyeller]

jack up one side of the rear end, with the transmission in gear. check the tire for any loose play. mine would move quite a bit with the worn out hub/axle. you could also try to turn the wheel. if its totally worn out, the wheel and hub will turn while the axle is held stationary by the opposite-side tire resting on the ground.

 

[Snitty]

if you have ANY loose drivetrain parts, it WILL cause vibration... I just got rid of some really nasty noises by simply tightening down my transmission mounts to the skidplate

 

[jay79cj7]

if you have ANY loose drivetrain parts, it WILL cause vibration... I just got rid of some really nasty noises by simply tightening down my transmission mounts to the skidplate

That's pretty much what I thought you would say... Its strange though, because it rides really smooth at anything over about 15 MPH.

I have grand visions of fixing this thing up in a year or three, new body, etc. I just hope it lasts that long because I can't do it now.

 

[Snitty]

sometimes when a part causing vibrations spins fast enough, the frequency of the vibration is too fast to notice