Freightliner - Meritor dfferential issue?

Check center bearing (carrier bearing) on drive line if it has one or up to three. ( you didn’t mention if it was a long wheelbase straight truck or just a standard tractor.)
If it has a fifth wheel it could be loose/ worn jaws causing the truck to lurch forward a little at accel. During decel the trailer is pushing against plate and not jaws so it tightens up so to speak.

I had a front spring rubber bushing were out on the rear hanger on my FL 60 that caused that same pop and lurch of the front end. It whould also pop during a full lock turn if it had a fully loaded front axle.
The bolts that go through the eyes of the springs in the rear hangers are so close to the fuel tanks that are mounted under the doors that the head was rubbing on it when the bushing went bad.

I would also mention clutch could be slipping but in your case with an auto that would not apply.

 

Make sure the driveshaft slip yokes are greased good. Check the axle u bolts. Look for movement on top and bottom plates. You’ll see a difference in the marks on any that are loose. Rear spring Hanger bushings might be worn. Usually the right rear will be worn the most.Along with checking the u joints, and leveling valve ride height.

 

If you feel the vibration when the noise occurs through the steering wheel, it's in the front end. If you feel it at your feet through the floorboard, its in the rear. Sounds like the the front spring hanger bushing area to me, like the others said.

 

I should have said, I had a similar problem where the clunk would occur driving straight, but most often when turning. I can't say I remember it pulling noticeably either direction, but that was so long ago. It turned out to be a worn front spring hanger bushing. I've heard Freightliners are common for developing play in the hanger bushings and thus wear out more quickly. A common fix has been to shim the bushing to get rid of that space between the bushing and the hanger when any knocking first develops keep the spring from sliding left to right and vise versa. Both a FLD 132XL and now my Century 120 have had that issue.

 

ATRO makes polyurethane anti walk bushings. They’re a very hard material, with grooves on the inside of bushing and on the eye. I’ve had them for a few years now. They’ve stayed in place. I’ve not been happy with ATRO polyurethane motor mounts, but I’d use the spring hanger bushings again. Solves that problem.

 

I know I'm raising the dead, but was wondering what kind of problems you had with their motor mount poly bushings? Was talked into using these and wandering if I'm experiencing same problems. Thank you.