3rd gen driveline vibration

[Alphacowboy]

Ok, here is something for you to all chew on. I did search, but all I found was that the dealer supposidly fixed the problem with a new D-shaft. In my case, that just aint going to happen. Heres the deal, I installed 3rd gen AAM axles under my 2000 2nd gen. Front and rear are in, and it drives pretty good. I had the rear all set up and no vibrations. The front however, after I installed the front d-shaft, it vibrites just like a 3rd gen. 60+ Mph, and it starts vibrating. The d-shaft was shortened ~3" to work with my truck (NV4500/NP245DHD) and balanced. The tech said he had no vibrations on the balancer. So... what else is causing this problem? Does anyone know of a fix (other than locking hubs... . trust me, they are next on my list when I get the money saved up) Looking at the setup, I think the problem is that splined yoke plate on the axle end. If the splines are not perfect, and there is any little amount of rust in there, it might not mount perfectly and be slightly off center? What ya think? I would have used the 2nd gen shaft, but I am pretty sure it was bent slightly.

 

[F-15I Ra'am]

Take the driveshaft off and reinstall it {rotate it 180*} opposite of what it was.

 

[Alphacowboy]

should I rotate it at the axle and t-case?

 

[F-15I Ra'am]

Would try it at the axle first, if it doesnt make a difference, then at the t-case also.

 

[betterthanstock]

A u-joint should have no more than a 3 degree angle. Take a protractor, and cut out a paper wedge of 3 deg, and compare to the angle you got there.

For the double joint, no more than 6 deg.



If you have a lift, and a shorter shaft, the angles may be too big. The only solution would be CV joints.

 

[Loren]

Alphacowboy,



There are several issues that can cause problems with driveshafts, but first I would like to ask a question. You didn't mention this in your post, but I assume that this vibration occurs only in 4-wheel-drive, right? You sound very knowledgeable, but I don't want to overlook the obvious. If the truck is not in 4WD then the front driveshaft is not turning on a 2nd generation truck unless you've modified it.



The obvious solution, that the driveshaft itself is out of balance, has been checked.



Next would be the phasing of the u-joints. I think that's what F-15l Ra'am is referring to. The u-joints at opposite ends of a driveshaft need to be in phase to avoid problems. They are in phase when the yoke on one end of the driveshaft is in the same direction as the yoke on the other end. That is, if you lay the driveshaft on the floor and one yoke is horizontal, the other must also be horizontal.



U-joints should have some angle when they are installed. It should not be too large. (I can't confirm the 3 degree number. ) A u-joint that is straight will often give problems.



Last, the two shafts that are connected via the driveshaft must be parallel to each other. They are obviously offset, or you wouldn't need u-joints at all, but they must be the same angle from horizontal. If your transfer case shaft tilts downward 5 degrees, then your differential input shaft should tilt upward 5 degrees. Otherwise the u-joints are partially out of phase.



Good luck finding the problem.



Loren

 

[sag2]

Alphacowboy,



There are several issues that can cause problems with driveshafts, but first I would like to ask a question. You didn't mention this in your post, but I assume that this vibration occurs only in 4-wheel-drive, right? You sound very knowledgeable, but I don't want to overlook the obvious. If the truck is not in 4WD then the front driveshaft is not turning on a 2nd generation truck unless you've modified it.



The obvious solution, that the driveshaft itself is out of balance, has been checked.



Next would be the phasing of the u-joints. I think that's what F-15l Ra'am is referring to. The u-joints at opposite ends of a driveshaft need to be in phase to avoid problems. They are in phase when the yoke on one end of the driveshaft is in the same direction as the yoke on the other end. That is, if you lay the driveshaft on the floor and one yoke is horizontal, the other must also be horizontal.



U-joints should have some angle when they are installed. It should not be too large. (I can't confirm the 3 degree number. ) A u-joint that is straight will often give problems.



Last, the two shafts that are connected via the driveshaft must be parallel to each other. They are obviously offset, or you wouldn't need u-joints at all, but they must be the same angle from horizontal. If your transfer case shaft tilts downward 5 degrees, then your differential input shaft should tilt upward 5 degrees. Otherwise the u-joints are partially out of phase.



Good luck finding the problem.



Loren

If he changed the front axle to 3rd gen, the front shaft is also spinning because there is no axle disconnect. Other than that, the advice given is sound, and should lead to the problem.