Loose steering in 04 trailblazer

Sounds like you have snapped the Pin in the front pumpkin or a gear has broken. Is their any clunking up front when in 2wd?

Checked how? Some AWD drive cases are fed fluid from the transmission. Some are separate. I haven't seen any rebuilt yet. these cases aren't much. The controls are in the rear differential and transmission.

Assuming no differential work was done because those ratio's must stay the same. Gear wind up is what causing the problem make sure all tire size's are equal. If had fluid replacement I hope you had the quad-trac fluid installed in transfer case. It is purple fluid and aftermarket has no equivalent.

It is possible that your transfer case is defective. The transfer case fluid needs to be changed every 50K miles. It is also possible that the transfer case actuator control/motor is defective. The 4WD system should be checked out by qualified technician.

When you switch from 2HI to 4HI, you should hear two distinctive sounds from under the truck, one is the transfer case actuator and the other is the front differential actuator. If you hear both and you still do not have power going to the front wheels, then there is a problem with the front disconnect assembly.

This year Jeep is famous for front and rear differential bearings going out, and it sounds like thats whats going on. If the transfer case were going out, you would hear all the grinding coming from the center of the car. If you are curious, remove the plate off the front diff.When the oil comes out,you will see lots of metal in it. Unless you rebuild differentials, you'll have to have it rebuilt.

What do the lights on the 4x4 selector switch do when you switch to A4WD or $HI or 4LO positions? Do they blink and revert to previous selection? Has the Transfer Case fluid been changed at 50K intervals?
There are actuators on the Transfer Case and Front Differential that control the application of power to the front wheels. These actuators are controlled by the TCCM (Transfer Case Control Module). It takes a qualified 4 wheel drive technician to diagnose these systems.

Transfer case fluid is a GM AutoTrak II fluid, use only this in the transfer case. For front and rear differential use a good quality gear lube 75W-95.

There may be more to it.. Transmission- P.T.O(Front wheels)-Rear Differential(Rear wheels). Or may have Transmission-Transfercase drives front differential(Front wheels) and rear differential(Rear wheels). So if one was rebuilt there should still be another that is still the root of the problem. Find out what exactly was rebuilt.

Here are the Fluid CAPACITIES & MORE:
Engine, with filter..........4.6 quarts[1]
Cooling System, Initial Fill..........12.0 quarts
Automatic Transmission, Total Fill
4 speed 4L60, 60E..........11.0 quarts
Manual Transmission, NV1500..........5.7 pints
Manual Transmission, NV3500..........4.2 pints
Differential, with 8.6 ring gear Rear..........4.0 pints
Differential, with 7.25 ring gear Front..........2.5 pints[2]
Differential, with 8.25 ring gear Front..........4.2 pints[2]
Differential, with 9.25 ring gear Front..........5.9 pints[2]
Differential, Front..........2.5 pints
Differential, Rear..........4.0 pints
Transfer Case,BW4472..........2.5 pints
Transfer Case,NV136/236/246..........4.0 pints
Transfer Case,NP207..........4.6 pints
Transfer Case,NP231, NP233..........2.3 pints[3]
Transfer Case,NV231/233..........2.1 pints[3]
1. After refill check oil level.
2. Do not use synthetic lubricant in axles using RTV sealant.
Synthetic lubricant will chemically atack RTV sealant.
3. Identification: check tag on case.