4x4 axle alighnment
 

My 68 K10 short bed drifts to the right ....The front end alignment is as it should be, all the parts are in good shape.
I'm putting in new bed wood any while the bed floor is out I measured the rear axle location off the spring hangers it was off nearly a half inch. After loosening the u bolts it was obvious they were loose in the past and the center bolt fretted out the locating hole. So the axle is now where it belongs.
I moved to the front, same thing the front axle was off about the same in a direction that would cause a drift to the right.
While measuring off the front spring hanger I see the center bolts vary by half an inch on left and right sides. The springs appear to be original unique type taper two leaf type...The spring bushings aren't distorted or broken...
Using the rear axle as a reference I enlarged the axle center bolt holes and shifted the front axle into position...
The frame has a two decent looking crack repairs done in the past but shows no accident damage.
Measuring diagonal across the frame in several places shows it's not jacked out of shape....
On the front springs, they are identical left and right, yes?

Re: 4x4 axle alighnment
 

Did you check to see if the frame itself was square first? Sounds like it got racked on one side

Re: 4x4 axle alighnment
 

Springs are identical on front as well as the pair on back

Re: 4x4 axle alighnment
 

Try rotating tires from front to rear and see if it still drifts. could just be tire wear doing it...

Re: 4x4 axle alighnment
 

I mentioned checking the frame on a diagonal , from the cab back and it was perfect.
The spring spring hangers are where they belong by measuring off the now straight rear axle as a reference. And it seems to boil down to one front spring having a different center bolt location than the other side.The design of the spring eyes means they can't be installed wrong. And the spring bushings are good and nothing is bent or broken...
I'm going to measure everything again today just to be sure...

Re: 4x4 axle alighnment
 

Sounds like a good mystery. I'mm curious to see what you find. I just changed the springs on the front of my '72. I'll measure the originals I took off. I am pretty certain they will be the same. Why wouldn't they be? And, I have replaced many springs on these trucks and if they vary, I never paid any attention or saw any issues

Re: 4x4 axle alighnment
 

I measured both front springs several times with the truck sitting level on axle stands...Right front spring center bolt is 22 inches from either spring eye... The left front spring center bolt is 21-1/2 from the front and 22-1/2 from the rear...very slight steer to the right...
It is what it is....I just adjusted the axle and call it good.
The front and rear spring hangers are true to the frame..