I recently had problems with 1st and 2nd gear take off vibration.
I narrowed it down the the driveshaft angle aft of the carrier unit (too much downward angle).

Well I installed about .5" worth of stock above the carrier unit and this has almost aligned both shafts together.
There is still about a couple degrees of downward angle after the carrier housing.

All take off vibration is gone.

My question: Can the shafts be aligned too perfectly? or should I have a certain amount of downward angle to allow for upward articulation of the rear axle?? (ie sledpulling, heavy loads etc.?)

?????
Thanks for the help!

 

is this the kinda stumbling feeling when taking off at a dead stop? i have this everytime weather empty or not. i dont know if its the tranny or what. to me it seams like the clutch doesnt know if it wants to engage or not for about 1sec. if this isnt what youre talkin about, anyone else have what im having?

 

is this the kinda stumbling feeling when taking off at a dead stop? i have this everytime weather empty or not. i dont know if its the tranny or what. to me it seams like a clutch or something deciding weather to engage or not for about 1sec. if this isnt what youre talkin about, anyone else have what im having?

 

Yes this is exactly what it is.

 

Mine is an 01 and I had a similar problem. Only it was when I pulled my trailer and happened when I was accellerating from say 60 up to about 68mph. Didnt ever notice it until I got my auto trans redone. Called the builder and he said oh yeah sometimes we see that with the longbeds and the 2pc drive shaft. He said to do exactly as you said. Lower the center carrier bearing housing 1/2 an inch or so. I did and it cured my problem. I have since added traction bars which will aslo cure that as well as the major spring wrap in the soft stuff. It is all that torque driving the pinion angle downwards(mainly because the blocks under the rear springs act like a lever) creating an even more pronounced drivleine angle and binding the joints.

 

The general spec on u joint angels are max 6 deg. When I get into setting u joint angels I try to set them to 2.5 deg. Make sure your u joints are phased correctly, as that will cause major vibrations. Many times a mechanic will reassemble the drive shafts and get them out of phase.

 

Hemi Cat,
What does phasing a u joint consit of? I have never heard of this. Thank-you.

 

Interesting I have 6" of lift and had clunking noise from front driveshaft after alignment man was done it's gone and I don't get any vib's from either driveshafts as back is two piece and angled down from carrier. For years on rising trucks I nevered leveled the two piece.
Lift has been on truck for about 4000 miles and I do alot of hwy miles.

 

Must be something to do with these 6 speed putting more torque to the ground.

 

I have been told that you need a little bit of angle in the carrier assembly because if the joints don't "work" flex they will dry out and wear out when they do get used. You don't want a perfectly straight carrier. Also I asked the dealership why my truck has little bit of stumble from a dead stop and I was told that I am actually feeling the pulses from the engine. I don't know if this was a crock or not. But I do believe to a sertain point. although I'm not sure.

 

Phasing the u joints is making sure the yoke ears are aligned on each shaft.On one shaft the yoke ears are in line with each other, then the next shaft is 90 deg from that. When you have a slip yoke you can put it together a few splines off and it is called out of phase. This causes the u joint action to counter itself and the movement is not smooth, and causes a vibration.
The u joints do have to have some angel to move the rollers to prevent galling of the bearings (flat spots). I use a magnetic protractor on the pinion, drive shaft, and trans to get the actual angels and do the math to set the u joint angel. I try to aim for 2.5 deg angel on the u joint. Hope this helps