normally i would agree with you about poor workmanship, but i've taken them to reputable shops (2). Plus they only work on Jeeps and 4x4's. Both shops couldn't tell me what is wrong or even a guess. Then again even good people, have bad days so they may have missed something.

Just for the hell of it why doncha tell us what gears you have and also what size tires. Is their a lift? If so what?
As a side note...I am not familiar with an "eleminator kit" What the hell does that do?
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

It's a slip yoke eliminator kit, basically just a beefier shaft for the transfer case and lessens the stress to the rear drive shaft. I have a 2' lift and are running 31/10.5 tires on it. I'm not sure what the gears are on it off the top of my head, but I try to keep the basic stuff stock so the parts are easier to get. I think that the gears are of the stock variety 3.14....sounds right.
Thanks to everyone for taking the time to help me out, other people perspectives and experiences are always insightful.

Ok I do know what that is.. Might have been terminology or perhaps even my age...
You prolly have a 3:07 gear unless that ride came with a trailer package. The 31's are a bit tall for that gear but not much and should be usable. I run the same gear with 30's from the factory and it runs well.
Others here use the same gearing and tire size without having the problems you are having. It is a mystery to me why you would have the problems you seem to have... particularly after confessing that you don't horse the Jeep around and mostly stay on the pavement.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

I would be for looking at was the engine re-build correctly done?

How about motor mounts?

You may have something of heavy weight shifting that is causing a binding downstream.....

the motor mounts were good, i checked those myself while the engine was out. I'm not following the part about shifting heavy weight, got the down stream part though. Never mind I get it now... Could bad transmission mounts cause this to get the drivetrain out of alignment when under a load (stopping and going) and causing my problems? Haven't really tinkered with 4x4's, have the basic concept, just not all the ins and outs.

Bad tranny mounts are usually noticed by the tranny shifting when under a load.
The check is to jack up the tranny from below and looking to see if it disengages from the crossmember..
The dudes that installed BOTH of the trannys should be aware of a bad mount as it had to be transerred to the new trannys..
As much work as you have had done to that part of the Jeep I doubt anything that simple would be the cause..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

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.

If the rear drive shaft was installed 180 out from the original position or has thrown a weight be enough to cause this kind of damage, but if that were the case I'm sure there would have been quite a bit of vibration associated with that. I think half of my problem is that I haven't looked at the system as a whole myself as far as how everything is mated together, it sucks that I have taken peolple at there word......live and learn. Is there anything in particular that I need to make sure of when I drop my skid plate this weekend as far as making sure that i have the "guts" of my drive system supported? Gonna be a long weekend.... <img src="/forums/images/graemlins/cheers.gif" alt="" />

As you installed a slip-yoke eliminator, was the drive shaft length checked?

Could the drive shaft be too long and bottoming out to cause undue stress?