91 pickup OME leaf spring question(s)
 

After a 4 hours for the first one, and 1 hour for the second, I got my new leafs installed. Two questions actually...

1. Whats the break in time/mileage and is there anything I can do to expedite the process?

2. Got a deep rumble at 20 mph that I didn't have prior to install...got me on edge listening for for new vibrations and sounds...

Okay, that was three questions.

Cheers!

They are Medium duty 1.5-2" lift....

The rumble could be a couple things but my guess is it's u-joint or pinion angle related. Raising the rear now changed the operating angles of those moving parts. Could be resolved with maybe a shim to change the degree angle, rebuild ujoints, or both. I needed neither on my truck.

As for breaking in the leafs, hard to say. I broke mine in by loading up the bed a few times with 800-1200lbs of compost, dirt and rocks, then the road I went on had some curves and "whoops" to cycle the suspension a little bit. I'd say it settled in quicker than most. I've heard of some people adding some weight and go cycle the leafs a few times on a ramp of some sort. Anything will help really. If you never put a load and simply drive around, I'd expect it to take months if not a year or longer.

The break-in height was a major unknown for me. It was suggested I install 6" shackles with the new leafs, I'm glad I kept my stock ones on. Current final height is 22.5" center axle to bottom of fender all 4 corners. Only now am I ready to go to maybe a 5" shackle and gain some rear height because tire hits at full stuff with weight in bed after I /\ my shocks with a ubolt flip.

Copy that. Any good recommendations on shims as far as manufacturer? Looks like I'm off 2 degrees. That said, I'm curious what angle shims to use?

auto parts store likely has the ones you need.

Thanks! While measuring the op angles i noticed the yokes on my prop shaft were NOT lined up...T/C end sits at 2 o'clock relative to high noon yoke on the diff. My first thought and rule is dont fix what isnt broken, but everything ive read says they have to be in line for proper cancellation of harmonic vibes. So mark the shaft on both ends before i pull it. Any other tips before i embark on this adventure?

They should be in line. I'd say pull the slip yoke apart and line up the yokes. Since your pinion and transmission are 2 degrees out of parallel you should shim the axle too. If you only fix one of these you'll still have vibrations.