Clueless and lazy, need input

[JayH]

I started having a vibration a few weeks ago that I thought was a ujoint in the rear driveline. It's not a vibe that shakes the whole rig, but it is one that insists on being felt throughout the whole rig - it's the roughest vibe I've ever felt and I've had plenty. It only happens when torque is being applied to the driveline, either through the motor or when engine braking is trying to slow the vehicle on a decent downhill grade.

I removed the front driveline just to be sure. The rear driveline u-joints are all in good shape. I removed the axles and carrier from the nine inch in the rear and all bearings were smooth. Upon reassembly the detroit performed exactly as it should going through the lock/unlock tests.

Changing pinion angle had no effect.

The vibration is felt at speeds aboe 25mph or so (regardless of transmission gear) with torque applied. As soon as I let off the gas, vibe goes away.

I'm thinking at this point that it is something internal to the Detroit but don't understand enough about the physics involved to know if that's plausible. Anyone have any experience?

If not that, I'm looking at the unpleasant job of tearing out, and down, the 231 tcase, and then on to the 46RH transmission. Input gear(s)/Output gear(s).

Just when the snow was getting to a fun level, too.

 

[jeeptech 1]

Have you checked all the mounts? I have seen the trans. mount cause this problem. Will the vib happen when it is out of gear and you rev.the engine to the same RPM the vib. happens? May be a torque convertor.

 

[uncoolperson]

no idea with jeeps, but for me this has been caused by

wheels/tires being goofy
lower ball joint
tie rod ends

sorry if none of this applies, it's just what i know.

 

[heep70]

Springs weak/bent?

 

[olllllllo]

I started having a vibration a few weeks ago....

Lucky!!! :cheer:



(oh, I was too lazy to read everything after getting sidetracked with your first sentence. Carry on. :

 

[KarlVP]

Have you tried pulling the rear driveline and driving it in Front wheel drive?

PS. If you are locked in the front. Do that in a parking lot somewhere. It's mighty shifty on the road with FWD and a front locker.

I had a U-joint go out on me. But it "looked" okay upon inspection. Then when driving down the road, it decided to die on me. Not a happy day.

 

[JayH]

Have you checked all the mounts? I have seen the trans. mount cause this problem. Will the vib happen when it is out of gear and you rev.the engine to the same RPM the vib. happens? May be a torque convertor.

Yup, all three mounts are fine; and no, I can rev the motor to any RPM with the trans in neutral and no problems.

I had thought torque converter at one point. Even more work.

Thanks for the feedback !

 

[JayH]

no idea with jeeps, but for me this has been caused by

wheels/tires being goofy
lower ball joint
tie rod ends

sorry if none of this applies, it's just what i know.

Ball joints are new (less than 2k), rod ends are as well (maybe 5k on them.) I doubt tires wheels but will keep it in mind. Thanks for the input!

 

[JayH]

Springs weak/bent?

Brand new in the front (maybe a 1000 miles or so,) and the rears are old and saggy but I would expect the dampers to take care of that.

 

[JayH]

Have you tried pulling the rear driveline and driving it in Front wheel drive?

DUH! Thank you! I didn't even think of that. Sometimes I have those bonehead moments. That's what I like about these forums. Thanks much. I will be trying that very next thing.

 

[heep70]

Lose nut behind the wheel. :redneck:


Sorry, had to say it.

 

[JayH]

Lose nut behind the wheel. :redneck:


Sorry, had to say it.

No doubt. an eye-dee-ten-tee error....

 

[crash2]

Have you tried pulling the rear driveline and driving it in Front wheel drive?

PS. If you are locked in the front. Do that in a parking lot somewhere. It's mighty shifty on the road with FWD and a front locker.

I had a U-joint go out on me. But it "looked" okay upon inspection. Then when driving down the road, it decided to die on me. Not a happy day.

Jay--I assume you have a slip yoke eliminator in the rig?

 

[JayH]

Jay--I assume you have a slip yoke eliminator in the rig?

Yup. Put one in the 231 about 6 months after I picked it up back in 2000.

I'm pulling the rear shaft and reinstalling the front shaft tomorrow in the AM. Will take it for a spin and see what she does. I'm half hoping the vibe is still there just so I prove myself not completely crazy - although it means more work fixing it...

 

[chrissybf86]

is there any dents or marks in the driveline's they might be bent.

 

[archer1965]

is this something that has been gradually getting worse or did it happen suddenly?

I would definitely have your tires balanced, you may have a broken belt inside which will do funky things.

you may have a bent wheel?

looking at the rig from the rear, does it have a lean one way or the other?
if the rear springs are saggy, you may have a broken leaf (sometimes not easy to spot).

 

[cheesemaker]

I'd be looking for something in the drivetrain! If it were a tire it would be at lower mph, and a tire out of balance would be all the time not only under accerelation!

Checked the pinion bearings? The output shaft on t-case still true! U-bolts tight?

 

[archer1965]

I'd be looking for something in the drivetrain! If it were a tire it would be at lower mph, and a tire out of balance would be all the time not only under accerelation!

okay Mr. Know it all

 

[bobbed_84_toy]

I bent the rear driveshaft in my old ranger and it had similar symptons to what your truck is having. Had just the slightest bow in it but it sure did drive funny:redneck:

 

[JayH]

Well, to further add to my embarassment:

I got underneath today to put the front shaft in and remove the rear one to take it for a test drive and see what was happening. When I got to removing the rear CV from the case, it had a very odd movement Sure enough the joint was toast. One of the trunions had a pit in it that must have been half a millimeter deep and a quarter inch in diameter. Man, I can't believe I missed that the first time.

Anyway, thanks to all for the suggestions. It's appreciated.