379 Transmission Issue

I own a '93 Peterbilt 379ExHd, DDEC IV 12.7, 18spd, 3.55s, 11r24.5s

In late May 2023, I decided to swap to a low(250K)mileage 18918spd from a 16713spd. I noticed my rear structure was leaking & I had a small vibration, too. So, I had my rears structure resealed & I also upgraded from a 2450 clutch to a 5500 clutch. The place I brought it from AND my drivetrain shop checked it out before installation. Afterwards, still had the small vibration & thought it was a ujoint going bad. I couldn’t locate the source at that time. But, the truck was shifting & running beautifully!

About 10 days ago, I developed a sudden chatter noise when crossing back into MD from PA & I could feel it through the shifter & hear it, too. But, it’s only in the the top 2 hole on the high side. I rode back to my drivetrain shop above the noise & the said my pinion bearing was going out. I had the back rear was rebuilt, minus the ring & pinion, with a new yoke. Picked up the truck, got on the highway & the chatter was still there in the top 2 hole.

What could the chatter possibly be from?

 

I'm gonna call Peterbilt & see what my ride height should be. I believe it's 11 inches, but I can't remember.

 

She makes 800/2850 at the crank...