Riddle me this

[b3uhbp]

Well yesterday I removed the shims on the rear and checked the angles on the yokes and found they were within 1 -2 degrees of each other. Buttoned it up and test drive it. Amazing improvement. I plan to do some precise measurements and see if I can get a little closer. In any case it is very good as it is. Just can't understand why the axle was ever shimed in the first place. The Tom Wood article was excellent and made me realize what my issue was. The angles must be equal, aka, the centerline through the differential and the t-fer case must be parallel. I'll let you know if I'm able improve further.

 

[Torxhead]

Thanks for the update. Driveline alignment is quite an interesting subject.

 

[b3uhbp]

You mean like the shims that were installed by Kong 4x4 in Phoenix Az on my 42 MB before I purchased it........

DS rear tire, before


After

My setup was pretty much like in you pics.

 

[b3uhbp]

Well yesterday I removed the shims on the rear and checked the angles on the yokes and found they were within 1 -2 degrees of each other. Buttoned it up and test drive it. Amazing improvement. I plan to do some precise measurements and see if I can get a little closer. In any case it is very good as it is. Just can't understand why the axle was ever shimed in the first place. The Tom Wood article was excellent and made me realize what my issue was. The angles must be equal, aka, the centerline through the differential and the t-fer case must be parallel. I'll let you know if I'm able improve further.

I may have mentioned that when I start the engine I get a thump and although removing the shims in the rear and getting the u-joint angles the same had a profound impact in reducing vibration, I still had a little when accelerating. Today I tried to see what might be causing the thump. I decided to take a fresh look at the tranny mount and noticed that the bolt going through the skid were in slots so I loosens the nuts and to my surprise I was able to move the tranny left and right about a half an inch. It had been all the way to the right/passengers side so I pushed it to the left and started the engine. No thump! Test drove. Zero vibration! It's hard for me to imagine that it would be that sensitive. What are Y'alls thoughts. Motor mounts is where my thoughts went again.

 

[b3uhbp]

Thanks for the update. Driveline alignment is quite an interesting subject.

I may have mentioned that when I start the engine I get a thump and although removing the shims in the rear and getting the u-joint angles the same had a profound impact in reducing vibration, I still had a little when accelerating. Today I tried to see what might be causing the thump. I decided to take a fresh look at the tranny mount and noticed that the bolt going through the skid were in slots so I loosens the nuts and to my surprise I was able to move the tranny left and right about a half an inch. It had been all the way to the right/passengers side so I pushed it to the left and started the engine. No thump! Test drove. Zero vibration! It's hard for me to imagine that it would be that sensitive. What are Y'alls thoughts. Motor mounts is where my thoughts went again.

 

[cardiffclimber]

I may have mentioned that when I start the engine I get a thump and although removing the shims in the rear and getting the u-joint angles the same had a profound impact in reducing vibration, I still had a little when accelerating. Today I tried to see what might be causing the thump. I decided to take a fresh look at the tranny mount and noticed that the bolt going through the skid were in slots so I loosens the nuts and to my surprise I was able to move the tranny left and right about a half an inch. It had been all the way to the right/passengers side so I pushed it to the left and started the engine. No thump! Test drove. Zero vibration! It's hard for me to imagine that it would be that sensitive. What are Y'alls thoughts. Motor mounts is where my thoughts went again.

The front driveshaft may have been hitting the case. Moving it back left gave it the clearance it needed.


-Andy

 

[Torxhead]

The front driveshaft may have been hitting the case. Moving it back left gave it the clearance it needed.


Interesting, just where would the front driveshaft hit? On mine I get a clicking noise when in reverse gear with the clutch disconnected coasting backwards and I cannot figure it out.

 

[cardiffclimber]

The front driveshaft may have been hitting the case. Moving it back left gave it the clearance it needed.





Interesting, just where would the front driveshaft hit? On mine I get a clicking noise when in reverse gear with the clutch disconnected coasting backwards and I cannot figure it out.

When I first brought mine home 15+ years ago, I engaged the 4wd and heard a awful clanking noise.

My Transmission mount was shot allowing the drivetrain to move side to side. I had a T-4 in it at the time and the driveshaft was making contact with the side of the Transmission .


-Andy

 

[cardiffclimber]

OP, I guess if you are experience this issue in 2wd, my suggestion about the front driveshaft would be moot.


-Andy

 

[Lumpy Grits]

If you can that easily move the tranny around. You need to replace both engine mounts, as well as the tranny mount and torque arm snubbers.
LG

 

[Hedgehog]

Clicking while rolling backwards can be the brakes moving backwards. Drum brakes are supposed to auto adjust when going backwards. On a few occasions I've had brake problems go away by backing up then hitting the brakes two or three times.

 

[Lumpy Grits]

You may have to do this 8-10 times, but worth a try.
LG

 

[b3uhbp]

Thanks for the update. Driveline alignment is quite an interesting subject.

It's been a while since I last posted on this issue so here's an update. Things are working pretty well but you know we jeep owners are pretty anal. When I am accelerating I still get a slight vib along with a harmonic resonance. The centerline of the differential pinion and the the Transfer Case are within .5 degrees of each other at rest (pretty close) but the working angles at the u-joints is 13 - 13.5 degrees. I'm told that 15* is pushing the limit for standard u-joints. Could my 13* angles be the problem with getting things fine tuned? Do I have to go to a double cardon joint?

 

[Lumpy Grits]

DC joint would be a good move.
Pull the rear DS and on FWD, see if you feel the same thing still.
LG

 

[b3uhbp]

DC joint would be a good move.
Pull the rear DS and on FWD, see if you feel the same thing still.
LG

That's what I'm afraid of.

 

[Lumpy Grits]

Easy way to test to see if that what's need'd.
If no change-Pull the front DS and test.
Even with be'n in 2WD and hubs unlocked. The front DS turns a bit.
Any chance this DS could be twisted just a bit? That would put the u-joints out of phase.
LG

 

[b3uhbp]

Easy way to test to see if that what's need'd.
If no change-Pull the front DS and test.
Even with be'n in 2WD and hubs unlocked. The front DS turns a bit.
Any chance this DS could be twisted just a bit? That would put the u-joints out of phase.
LG

The DS is brand new so no issue there. Also, if the front DS rotated I doubt it would ever be fast enough to cause a vibration. Here's my theory.

As I stated earlier, the ujoint angles are only off by .5* at rest. But, when the driveline comes under a load the pinion tilts up by 1-2* making the working angles of the front and rear ujoints out of sync by 1.5 -2.5*. That could be enough to cause the vibration given that the angles (13*) are pretty steep/nearing the limit.

 

[Lumpy Grits]

A DS mis-phase(or 'clocking')becomes apparent PDG from the Stop sign. So does to steep an angle.
Put the rear DS on a known flat surface a see if the yokes sit flat on both ends. If they do-Your GTG.
I think you're gonna have to go to a DC joint. Put that up at the tranny yoke.
LG