U-Joint and Vibration

Ok.. couple things. I get a vibration only at about 45mph to about 50mph. if i take all torque away from driveline its smooth so I knows its a drive line issue. I just added a 2.5 inch lift and now i get this vibration. I have attached a pic. For number 1, the yellow arrows show I am 90* out of phase, so I will fix that, but it was like that before and I did not get the vibration. the number 2 , white arrow shows the fatter half of the drive shaft on the lower part, is it back wards? should the fatter part be near the TC? I added one shim to the rear axle when I did the lift but i am still not sure I have the angles right. I did look here http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html but with everything installed on the jeep its very hard to get the "straight" line to do the measurments.. any suggestions? Thanks ahead of time.

 

We always put the splined collar like you have it so that mud does not run into and accumulate in the slip joint. Just looking, it looks like it is a spline or 2 off of parallel between the front and rear u-loints. you can take the whole shaft out (just loosen the 4 u-bolts) and lay it on the pavement to check this. Then mark it with a punch or crayon which splines line up for reassembly under the jeep.

 

Funny, thats what i was thinking when i installed it.. so.. I'll tear into the angle of the dangle in a day or two and see if i can get that alignment right.

 

Lifting the Jeep with the driveshaft out of phase would compound your vibes. Your angles don't look bad, if I was to guess based on the pic I'd say your rear pinion is a touch high, but I wouldn't change anything until the driveshaft is in phase.

I usually see the driveshaft the other way, might just be for more clearance closer to the ground though.

 

Thanks for the info, So what I'll do is fix the phase first, test drive and then i'll drop the tranny a tad i think. easier then taking the shims out.

 

Dropping the trans will make it worse. If you drop the trans you will need to drop the pinion angle. It should look like this. Transfer case and rear end should be in the same plane, equal angle on ujoints. The only way you can keep the rear pinion angle the way it is and drop the trans is to use a CV driveshaft.



The only way you can keep the rear pinion angle the way it is and drop the trans is to use a CV driveshaft.



Hope that helps.

 

My observations:
1. U joints are running at separate angles between tcase and pnion, as previously mentioned. You may need to remove the degree shims at the axle to correct this.
2. U joints are out of phase, as previously mentioned. Remove driveshaft and rotate slip yoke around on splines.
3. You may have a worn slip yoke. With the driveshaft mounted, push up and down at the slip yoke. How much play does it have? It shouldn't be more than about .010". Adding the lift kit extends the slip yoke, exasperating any wear that is present here.

 

Dropping the transfer case will effect the drive shaft to diff pinion angle but not near as much as the transfer case output to drive shaft angle. Basic geometry. Dropping the transfer case very well may fix the problem. The longer the drive shaft the less the effect on the ds to diff pinion angle in this case. I'd drop the transfer case and re-measure the angles. You want as close to equal u-joint angles between the drive shaft and transfer case output and drive shaft and diff pinion as possible. It's ok to have the drive pinion for the diff about a degree lower as the pinion will climb somewhat under acceleration with a leaf spring suspension due to spring wrap.

The angles shown in the pic show too much of a difference in the u-joint angles between front and rear.

 

It's almost impossible to know what angles are there now just by looking at a picture, they need to be measured before making any changes, correct?

 

There is no difference bewteen the front and the rear u-joint angles in the picture with 2 conventional u-joints. The axis of the transfer case and pinion are drawn parallel, and any line intersecting two parallel lines has the same angle at both ends. Maybe it's an illusion of the drawing, or are you saying that the pinion should be tilted down slightly, ie 1 degree?

 

Yes, that makes sense. The angles have to be the same.

 

Did you reclock the shaft yet??????

 

re-looking at the pic posted by buddhaventura, I have to agree. The angles definitely need to be measured front and rear after the drive shaft is re-clocked. May have been my tired eyes making the front angle look steeper than the rear.
The angles need to be as close to the same for the front joint as for the rear joint as possible. A simple Harbor Freight or Sears angle finder can help with determining the angle of each joint between the yoke on the transfer case and diff and the driveshaft.

 

Ok All, Thnak you very much once again for the help.. Vibration solved!!!! Finally.. Was the drive shaft out of phase. 5 minute fix.. woowowowwooo hoooooooo. One of these days I might actually get to not worry about anything, I hope soon, cause I am taking it from where I am now in Cancun Mexico to Panama... Do or die!!.. just a 2 month trip.. safer then in my RV. Again Gracias.

 

Excellent!