Backstory- I have an 04 silverado2500HD The transfer case required is an MT1, about 1k for a pulled TC. Its been rattling, random gear grinding, random reverse not working. So, 6/20 we pulled the TC case off and the mode fork was toast. Ground down to nothing, filter and magnet full, fluid was dirty. We tore apart an NP261 and used the mode and range fork, slide and oil pump from that into the TC pulled off of the truck. The part numbers were the same, looked like the only difference between mine and the 261 was the drive shaft and the chain. Both are larger on mine. After we rebuilt the truck ran beautifully. Smooth and better control. on 6/27 I set off across the state, was about 20 min from home coming off the bottom of the mountain and the truck would not accelerate. I coasted to a stop on the shoulder, tried shifting, no movement at all. Engine would rev but nothing. Could not shift into park without gears grinding. I ended up in neutral with the parking brake on waiting for a tow. We got it home and after playing with it was able to get gears caught between 4l and neutral then drove it into the garage. Tore the TC open and the mode fork was practically melted. End busted off, pad in pieces, filter and magnet full.
Ive found an updated version of the mode fork that comes in a kit with a slide and fork pads.
Now, WHY was the mode fork destroyed? The part was brand new. No way to tell if the rest of it was new or just really clean but the 261 case shifted nice and mine did as well before we installed it. We used transmission fluid in the TC, 2 quarts. No driving issues at all until it failed a week later. Im currently waiting on parts to rebuild the TC again. But any clue why it failed? And how do I keep it from failing again?