Vibration problem

[Leper]

Also, sometimes idiot DPOs will re-bolt their driveshafts to the ujoints 180 degrees out of phase when replacing joints, causing driveshaft imbalance. Try unbolting and rotating the shaft 180 degrees and rebolting (try both ends), if you haven't already.

I don't understand this statement. The ujoints only go in one way. Don't they? My ujoints press in to the driveshaft.
Please explain, because I still have my vibes. Shackle flip, bad vibe, then 6* shim, tcase hits the floor on hard accel from a stop but no vibes, then replaced with a 3* shim, Got more vibes back 24 mph and 50 mph. I am replacing the tcase mount tonight I hope and going back to the 6* shim.

 

[ZZ4x4]

On a slip jointed driveshaft, the yokes at each end of the driveshaft must be in phase so the two end's rotational forces counter each other. It's part of the balance just as having the same angle at both ends. If you pull the driveshaft apart and slip the splined section back in out of phase, it can cause vibration.
But ,you have a slip joint t-case right and the driveshaft yokes are welded to the tube so probably is not your problem.

 

[K5Steve]

I;m going to have the driveline lengthened.It is stock length and there is about 3 1/2 - 4 inches of visable slip coming out of the t case.I am pretty sure now that is where the vibes are.I just put in new spicers,balanced the d shaft,and put a new slip and pinion yoke on and it was still vibing.I lowered the t case and it isn't as bad now.It is more noticable accellerating up hill and decellerating down hill(foot off gas).

 

[Leper]

On a slip jointed driveshaft, the yokes at each end of the driveshaft must be in phase so the two end's rotational forces counter each other. It's part of the balance just as having the same angle at both ends. If you pull the driveshaft apart and slip the splined section back in out of phase, it can cause vibration.
But ,you have a slip joint t-case right and the driveshaft yokes are welded to the tube so probably is not your problem.

OK Thanks for explaining that.
BTW my slip yoke is sticking about 5 " out of the tcase. I am going to have the driveshaft lengthened a little,, because I don't think it is slipping at all. On medium to hard accel the tcase hits the floor(and the mount is good)

 

[K5Steve]

Well,I had my d shaft lengthened from 29 1/2 inches to 31 inches and now 90% of the vibes are gone!I'm sure what ever there is left is the rear springs.They are lifted with blocks and the eye bushings look pretty worn so I'll order some 4 inch lift springs sooner or later.I want 6 inches of lift if I keep it so when that time comes I'll order a shackle flip.When I downshift it to 2nd I can feel the rear move around some,everything is tight.It s pretty much all gone now though,just an update.

 

[Leper]

Thanks for the update. That is the point I am at also. I hope the slipyoke doesn't break this weekend while I am wheelin.( broke 1 already in Gilmer) I will have mine lengthened next week.
Btw how did you come up with the amount to lengthen the shaft??

 

[K5Steve]

I measured from the center of each u joint yoke at either end of the d shaft(29 1/2") and looked at the slip to see how much it need to go in the t case and got the differencee(1 1/2") for a total of 31".Plus I know a guy with the same lift and his is lengthened and I also got the measurement off of his.

 

[Logun]

I have that same problem with my 89. It's got six inches of lift and angled shims in the rear...but I know the driveshaft angle is too steep at the tranny end. Double CV joint might fix it?

 

[Never Satisfied]

Where is a good place to buy the shims?

 

[tch777]

Balance the driveshaft before you do anything else, sounds just like my vibe issues, the drive shaft was off and kept trashing out the U-joints and eventually wasted the pinion bearing.


Tim