I agre with BigJim. If the front and rear axles had different gear ratios, you couldn't get it out of your driveway in 4WD.

Also, I strongly suspect that the shop that's doing the work in replacing parts for you is doing something wrong. Something is not getting secured or is being misaligned on assembly.

1977 CJ-7, fiberglass body, AMC 360 w/ headers, DUI ignition, Edelbrock intake and Holley 4150 carb, TF999, Dana 300, 4.56 gears lockers, York air comp, 4" susp lift, 2" body lift, BFG 35" M-T tires, Megashifter, AGR pump & box, REP8000 winch.