Need help badly. Transmission or transfer case

[Kyknight40065]

Hey guys. I need your help. I have a 2003 4.2 v6 trailblazer 4wd LT. Two days ago I was driving up an incline in 2hi at approximately 60mph and tapped the gas to downshift the transmission to climb the hill. As soon as the transmission downshifted, I heard a noise. The transmission immediately started slipping and would not engage. I immediately pulled over and heard a spinning sound that lasted for about 30 seconds and stopped. I now do not have any gears at all forward or backwards and the 4wd will not engage. The selector button moves and the lights move to their respective locations. My question is what broke? Did the transmission go out or was it the transfer case even though I was in 2wd? I'm hoping someone has had a similar experience. I would hate to replace the transmission if it is the transfer case that is the problem. It's like everything is in neutral except park. Park works like it should, but nothing else. I dropped the tranny pan and the fluid looks good and there was no metal in the pan. Can anyone point me in the right direction? Right now, my only option is to replace both the transmission and the transfer case unless I can figure this out.

[Jrgunn5150]

It has to be the transfer case. There's absolutely no sensor or anything that can make it lose every single gear at the same time and neutral the way you're describing that I know of.

What's the history on this vehicle? Has it been maintained properly? When you say you were climbing a hill at 60 mph... You mean while driving down the road right? Lol.

[Jrgunn5150]

Eh, I thought about it a bit. You're getting no action, in any gear? Just free revving? No matter the transfer case range or shifter position?

[Aries]

Transmission. I have dealt with it couple times, I just replaced the trans in my replacement TB. You could drain the transfer case and inspect the fluid.

[Kyknight40065]

Yes, regular driving down the road. I did a trans flush and new filter a few weeks back. Yes, free revving in all gears even when the transfer case is switched on in the cab.

[Jrgunn5150]

It seems like something on the input side, flexplate, converter, input shaft.

[Regulator1175]

If your transfer case broken you would not have park. Do you get anything in commanded gears 1 or 2? Either way you are looking at a rebuild, but it would help narrow down the problem.

Read here: 30 common transmission problems

From what you describe it sounds like these can be your potential problems.

19. Loud bang, grinding sound, loss of all gears, and a binding driveshaft: Snapped output shaft. Try to wiggle driveshaft - if more than 0.020" play, that's the sign. Must be removed and transmission rebuilt.

21. No movement in any gear: pump failure, or total loss of fluid. Remove transmission and rebuild, or refill pan and find the leak. If out of fluid, avoid running the engine until the transmission is refilled to avoid pump damage. To check for pump failure, check fluid level with the engine off, then start the engine and recheck fluid level. If level does not go down when engine is running, the pump is broken.

[NC_IslandRunner]

My transmission stopped once too, no loud noise that I can recall but nothing in any gear would even try to move me. The transmission fluid pump broke and the transmission completely shuts down to prevent damage, new pump and I was back running.

[Kyknight40065]

Thanks everyone!! So now I know it is the transmission. I do have another question. The plan is to replace the transmission with one from a salvage yard. My question is what years and models are compatible with the 2003 trailblazer 4.2 LT 4wd? Which ones are direct replacements? I'm hating it, but I see trading it off once the transmission is replaced.