I lengthened the frame on my dump truck when I put it together and had to add a second shaft and carrier bearing. I've always had a slight vibration and it finally took the rubber out of the bearing. The first shaft has the carrier bearing and the yolk that bolts on. I had the ears lined up and thought this might be the problem so I moved the yolk 90 degrees to line up the moving parts of the u joint. This didn't seem to help. Does anyone know the correct line up of the joints and if the drive shaft needs to be straight from trans to rear end. It does seem to not vibrate as bad if I am loaded heavy.
Air ride? Or, is the front flattening out when you're loaded, causing angles to change? Maybe your front is sagged down? These suggestions only pertain to a twin screw....
If I remember correctly 7.5° is the magic number. Prop shaft off trans to carrier cannot drop more than 7.5° from horizontal. And from carrier to pinion cannot be 7.5° from horizontal. You were probably too high of an angle and it only calmed down under heavy load because the axle couldn't "rise up" under throttle. Now I assume you were talking about driveline angle and not u-joint timing. But if that's what you meant, all crosses must be square to one another. Not angled or perpendicular, ...square. If I'm wrong, lets hope DMiller or truckshop catch this and tightens us up on the details
Set the front shaft at 2.5 to and second shaft at 4.5 normally works. Yokes lined up end to end. Does the axle housing have caster shims in the u-bolt saddles? If it was a short wheel base the input yoke on the front drive or single drive may be tipped up too much, common issue when lengthening a truck.
So 7 total, not shaft to shaft?
It does have shims under the springs, it's a four spring international. If I take the shim out of the first axle will that affect the second drive shaft? I know the u-joints have to be lined up but does it matter which joints line up? I'm saying the u-clip verses solid.
If you can look at other trucks and study them . Its a lot easyer than trying to make cents of what someone is trying to tell you.
A little long-winded but informative.
Whatever change you make to your power divider will affect your rear drive .
If you lessen the angle on front drive by changing caster shims the rear drive will need to be altered the same amount.
Kind of complicated for a simple man like me. The first carrier lasted 10 years, I'm 63 so I might just let it vibrate and last me out. Seriously I think I'll start dropping the carrier a half inch at a time and see if that does any good. The hydraulic pump is close but I think by grinding one of the lips off the carrier outer housing I can make it clear. That seems like the simplest thing to start on.
A good simple illustration of pinion alignment and u-joint phasing.
It doesn't have to be too far out to do damage. Had a driveshaft repaired on one of the trucks once. I think they just pulled it apart at the slip joint. Put the repaired unit back together went back to work. Driver noticed vibration, kept driving. Destroyed the carrier in less than a week. The real truck mechanic noticed the yolks out of alignment as he changed the carrier. Only a couple of teeth out, but it was enough.
Go to a drive line shop they will fix you up