Miserable shaking and vibration.. Rear end? (1 Viewer)

[peiserg]

Guys, my 1975fj40 with 4 inch old man emu lift and extended shackles is on 33 inch AT's. Been shaking violently on freeway above 40. Just had tires rotated and balanced and front end alignment with no change. Took in to a friends shop and he turned it over to his master tech..

Just got this text


My tech is saying its either an axle issue or something inside the differential. Nothing suspension wise is worn except the leaf spring bushings on the front part of the leaf spring. The left side bushing is starting to come apart and the right side is very minor. Both have no movement with a pry bar. We tested it while its up in the air and the whole rear axle shakes violently. So we removed the tires to see if maybe one was out of round and causing the shaking and that didn't make a difference.. The whole rear axle would do the same thing. Suspension is good, so is both drive shafts, and u-joints.. He did notice the rear axle is shifted to the right and the right wheel has a two finger gap between the wheel and fender and the left has about 3 finger gap. Tires are pretty much at a point where they need to be replaced based on the center tread depth but as much as you drive it you probably don't have to worry to much about them. They don't look super dry rotted just minor cracking... Unfortunately we don't do anything with differentials.. My only option would be to remove the whole thing and send it out to AZ rack and axle or AZ differential...



Not sure what to do...what do you guys recommend? Truck is almost nondriveable

 

[peiserg]

As an edit, just received this info

He said the axle can be recentered and could of been shifted maybe due to some hard off roading or just age of the vehicle. We would just have to losen the u-bolts on both sides and center it. Bearings don't have any play side to side or up and down so that's definitely not it. I'm going to make some calls to some axle shops and see if they've seen this before and what their thoughts are.

 

[shawnfj40]

The springs have alignment pins. The axle should not move side to side.

 

[78fj40mg]

Have your mechanic check the following:

1. Tie Rod Ends for excessive play
2. Steering knuckles may need a rebuild, if they're leaking oil the seals are toast
3. Make sure drive shafts are in phase, also check U joints
4. Steering dampener may be worn out
5. With a 4 inch lift is the drive line angles correct, may need shims to correct angles front and rear, incorrect drive-line angles will result in rough vibrations
6. Also check steering center arm may need adjustment or rebuild
7. Wheels bent or bad tires, warped rotors will have similar vibration and shimming affects
8. Check steering rag joint for wear

 

[tlc762]

Agree with what Mike said above. I'm leaning towards axle caster shims due to the lift height and use of extended shackles.
HTH,
Will

 

[peiserg]

Maybe i can clarify... He said (as per the above text) that while up on the lift, the rear end is shaking. He ran it with and without tires and there was no change. He said all shaking is in the rear while up on the lift.

The lift has been in place for 10 years with no issues,along with the castor shims.
I do have a custom driveshaft thats been ok for many years.

 

[Mace]

which bearings has he checked. U joints?

 

[peiserg]

Bearings would be the rear axle bearings as i understand it from the above texts. He did indicate that they checked the rear ujoints as well

 

[JohnnyC]

he put back the drive shaft out of phase IMO

Was the lift just installed ? ... I read it as that had just been done... If so then he could have put the shaft in wrong

 

[Mace]

So, was anything done to the truck right before the shaking?
or did it just develop?

 

[peiserg]

Iirc it just developed. I did have new rear shocks put in, and a little while ago i had the spring stack greased to try to make the ride a bit smoother. The lift itself is 10 yrs old, including springs and shackles. Wheels are 10 yrs old. Tires...maybe 5 yrs.

I did wonder regarding the driveshaft phase. How can i tell of its out?

 

[JohnnyC]

If you didn't touch it ... Then it's not that

 

[Fast Eddy]

It would be easy for the mechanic to pull the drive shaft and spin the rear end (tires off) with an air impact gun. That would eliminate the driveshaft from any potential issues. Google "drive shaft phase site:ih8mud.com"

 

[Mace]

Are the U bolts tight?

Honestly, if it's the third, pull the rear cover and take a look, it'll be obvious..

 

[honk]

Are the U bolts tight?

Honestly, if it's the third, pull the rear cover and take a look, it'll be obvious..

Yeah, and ask your guy if he can move the pinion shaft side-to-side with the driveline removed. Two good bearings support the pinion and it's rare they fail but if the front one went he should be able to wiggle the shaft and if the rear one went there will likely be an unusual amount of metal inside visible once the cover is off.

 

[Mace]

I figure that if they checked the rear U joints, the pinion would show up..

Course..

 

[78fj40mg]

Here's the driveshaft phase

Courtesy of @lostmarbles

Courtesy of @1911

 

[brian]

i can't see how anything being that far out of whack in the rear to create that much shaking, would actually allow the rear to even turn.
i'm thinking you have a better chance of fixing this, by finding a mechanic that knows what hes doing.

 

[shawnfj40]

I agree with Brian. Your mechanic should be telling you what he found when he pulled the rear cover. If he didn't, you might have the wrong guy.

 

[Weber Sarge]

For one thing - if they are spinning that axle with it hanging on a lift and allowing the axle to droop , well , that's going to bind those u-joints something fierce if not destroy them . Need to do this with the weight on the axle with stands , not hanging free . Also , they should be inspecting the slip splines in the rear shaft as well as the pinion in the gears - if either is loose it allows the shaft to wobble out of line . If those spring bushings or just 1 is bad enough it could allow the axle to run at an odd angle creating more vibes but that is rare . Need to make sure everything runs straight in that drive line back there including the t-case output shaft .

Sarge