You must have some slack inside the t-case.
I'd get the rear wheels off the ground, crawl under and twist the driveshaft back and forth, you may hear noise inside the t-case (leave the transmission in park).

 

And if there is slack. I take it the t-case will have to be pulled and adjusted to take the slack out. As of it is now there is no slack at all but the rear tires are on the ground

 

With the wheels on the ground, the rear diff play is going to limit the amount of twist in the driveshaft.

And I don't have any advice on the adjustments in the t-case, I've not had one apart.

However, it has been my experience that if a problem did not exist before something was rebuilt, the problem is probably tied to the rebuild.

Therefore, the problem must be due to the rebuild. I don't know if there are any adjustments inside the t-case, but I'm sure there are a number of measurements that must be checked and placed into proper specs.

 

ujoints good / rear diff does not make the rattle.. transfercase has a bad new part ... could be the electric motor on the transfercase also..

 

The t-case only got a pump upgrade and new seals.
u-joints done in not to long ago with carrier bearing and the flex clunk is only right there at the tcase output. The rear second part of the drive shaft doesn’t move

 

my guess is the transfer case does have part failure .

 

Well, when it clunks when put in drive, transmission is coming out of park, it goes to reverse, then drive, first gear is engaged, but it clunks and ready to move once your foot is off the brake pedal.
In reverse, the reverse clutch is applied then sunshell engages the second gear set sun gear while the output carrier is held by low-reverse clutch. When put in drive, reverse clutch and low-reverse clutch are released and forward clutch engaged. A clutch is delayed releasing which explains the clunk.
I believe it's a transmission rebuild issue. Probably clearances on clutches could be out of spec or apply pistons leak delaying clutch release or engagement.

 

I just got a code for a stuck e solenoid closed p1711

 

did you use a code reader that indicates drive train/abs GM codes ? the p1711 has a solenoid in the transmission and also the wiring / connector on the transmission... check the transmission connector and wiring to/from the transmission..
when the transmission valves wear out over 10-15yrs because DEXRON III CREATES ACID AND WEARS OUT THE VALVES AND THE SHELL ..I dumped Dexron III in 2001. my truck 2000 new changed the fluid to synthetic mobil dexron/merc spec.many GM trucks have the shell cracks in our truck model years..

 

Who rebuilt the transmission?
Should be covered by a warranty?