Aluminum driveshaft harmonics

[ChrisKringle]

Have an aluminum driveline on my truck, off of a dmax. Ever since I lifted it, I have a rythimic noise coming from it. It increased in intensity with throttle, and only does it on the freeway. When the torque converter locks, it becomes much more noticable. Also, the more load, the louder it gets. Thought it was a u-joint. Pulled them, one bad, so replaced them all. That did not fix the problem.



The shaft was balanced when I had it chopped and welded. Gave me not problems till lift. So when I lifted it, did it pull it out further on the splines, causing it to ride different?

 

[Bob4x4]

Sounds like you may need to repair some angles if it happened after the lift



Bob

 

[sag2]

If it didn't occur until the lift, it is angles. You most likely need to lengthen the center support bracket. See TSB 03-003-04 for the different length brackets. They fit all the way through current trucks, even though the TSB says 03-04.

 

[ChrisKringle]

Actually I do not have a center support bracket, I have a 1 piece driveline. I do not have a harmonic balancer on either end. I noticed Chevy's have one down on the axle end, not sure about the t-case end. I know my factory unit had one on the t-case end, think it was pressed on the splined output yoke. Shop took it off. Is this the prob? Anybody had harmonics after lift?

 

[Vaughn MacKenzie]

I would start by verifying the driveshaft angles at the U-joints as mentioned . . . ie, driveline phasing. Angle at output shaft U-joint needs to be the same amount as at the differential Driveline 101

 

[ChrisKringle]

Hey Vaughn, thanks for the 101 link. I think I just found my problem by reading it. Assuming you lift the rear of the vehicle with either blocks or springs (4" blocks for mine) then the angles on either end of the driveline stay equal to one another, but increase slightly. So, you should not install shims to change the pinion angle because the angles are already phased correctly, and they remain equal. Well, Les Swab did install shims, probably the shims that came with the tough country kit. So I am going to pull the shims tomorrow and see what happens. Also, I am running the Tuff Country anti-spring wrap bars that bolt on the top of the u-bolts and at the front spring bracket. They cost me about $130 and they work great. I just got back from desert trails and mud, no hop or bounce whatsoever.



So anyone else have the shim issue?