Hoping maybe you guys could help point me in the right direction here. Have a '99, auto, 4wd swap from a '00.

At​​​​​At the time I was completely stock. No issues with anything, smooth swap. Since, I have a 4.5 LA full lift, and SYE.

Lately I've noticed while driving if I pop it in 4hi, on decel around 30 I have a gnarly roar/whine. If I'm on the accelerator, no problems. While on decel if I pop it back in 2hi, I hear the case switch and sound is gone.

I have a LP Dana 30. There is no play whatsoever from the front pinion, no side or in-out. However the pinion seal is leaking. I have just a hair in-out movement from the front yoke on the t-case. All fluids are new, probably within the last 1k miles.

I'm thinking possibly front pinion bearing? Any help would be greatly appreciated.

 

I would check your front drive shaft first

 

I wouldn’t rule out the transfer case either.

 

When I was trying to pinpoint it earlier, was on a bumpy road. Noticed the sound would go away whenever I was going over bumps, assuming with articulation.

The driveshaft that is on the front was recently in the rear, and it had no noise.

Am I supposed to have any type of play on the front yoke, in-out to be exact? Perhaps the yoke nut is loose, since I did do the SYE. I'll check that out tomorrow.

 

So I put the jeep on the lift at work today, supported by the axles so wheels could turn freely. Put it in 4hi and let everything roll. Absolutely quiet. I noticed the front axle favored the left wheel and the right was stopped but tried to turn every second. No noise from the t-case or the front axle. Couldn't coast, and that's when I have my noise.