Tcase took a dump?

[Z28TWITCH]

So, long story short, took truck for a test ride after readjusting some stereo stuff...noticed that it had a real bad stumble/rumble but only when I got into it a little bit. Get the truck home, back and forth in the driveway and get a god awful squeaking sound from under the truck. Put it in the air and put the brakes on slightly to add some load...sure enough, squeaking, grinding, bucking, awfulness. Sounds like someones trying to polish rocks with buckshot in a steel drum. Anyways, am I correct in thinking this is the transfer case making all this racket? Ujoints are mint front and rear, just did them 4 months ago and can pick myself up by the driveshafts with no movement.
Just to be sure, the transfer case is an NP246 correct? I can get one for about $300 with 80k on it...OR...should I tear it down first and see if it just needs to be rebuilt? Thanks

 

[retiredsparky]

$300 is a good price, change out the fluid in the replacement one. Install the pump rub fix before install (less than $50 for parts including seals). The oil lube pump was designed in these transfer cases to guarantee GM lots of replacement sales later in it's life. Google GM pump rub. That might be what took out your old one. The pump gear will grind through the housing after the thrust clip (which should be a big flat washer) wears out. Thanks GM!

Larry

 

[rockola1971]

The typical scenario is the pump rub gets a small hole ground in your Tcase rear section on passenger side of it just about a few inches above. Eventually enough fluid leaks out and this is what ruins your output shaft bearing. That is probably what is making all the noise. Its a needle bearing. The rest of the bearings are ball bearing.
You can pull the rear case off, install the pump rub fix spacer, replace the output bearing and be back on the road or spend around $250 in parts for a full rebuild which includes clutches, new chain, all bearings and seals. Only "special" tool needed is internal snapring pliars with a longer than normal reach. Your Tcase is a NP246E. The NP246 was an earlier model.

 

[Z28TWITCH]

So, I got under there and pulled it out. Then tore it down, checking and bagging stuff as I went...only things that jump out at me are the clutch housing is all burned (different blues, yellows, and blacks)...the needle bearing in the case had a roller or two fall out as soon as I touched it, and the output shaft wiggles like a sumbitch when you touch it...

Now, to me, everything except the clutch housing LOOKS acceptable...even the clutches still seem to have a fair bit of meat on em...I'm starting to get nervous that the transfer case is fine and my problems lie in the transmission...I'm picking up a tcase out of an 02 tomorrow for a few hundred bucks and I'm going to roll the dice...just banging my head against this one because nothing else makes sense...no pin hole in the case, fluid looked GREAT, still same blue shade as when I put it in...no chunks or pieces fell out at me...bearings, clips, gears, everything where it should be...this is gonna suck if that trans is garbage...

 

[Z28TWITCH]

rockola1971,,,I believe you nailed it...no pump rub, still has the "anti rattle" clip...no shiny spots...nothin...BUT, i placed the two halves back together with no chain installed...front output sounds like its filled with sand...sure enough, roller bearing fell apart as soon as i seperated the case again...im pretty confident it isnt supposed to do that hahaha...any rate...new tcase tomorrow, still a little nervous because we put the transmission in 6 months ago...well see i guess...thanks fellas