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I recently acquired a 98' M1078 with the WTECIII. It has an issue which I believe is focused on the transfer case (mechanically). The truck will start and go into gear, both Drive and Reverse, but it will not move. The transmission engages appropriately and puts a load on the engine but the truck does not move. It feels like one set the parking brake and put the truck into gear. The truck will not move when the engine is running, even in neutral, if pushed or pulled by another vehicle. No amount of throttle, mode on/off, or shifting of gear will release the truck from this state unless manually down shifting into 1st. The truck goes into 1st easy and the truck suddenly unbinds and can drive in that gear.
The transmission fluid smells burned, obviously not good, and some fine metal particulate attracted by the pan plug and filter. No large chunks or notable pieces of things. I've drained the fluid and rinsed with 10w to see if anything else would be flushed out but nothing notable. Oddly, when I started the truck it went into reverse and moved about 20 feet before coming to an abrupt stop. I was unable to replicate this and assume a pocket of air finally filled somewhere and something locked up being the issue here.
I've pulled the plate next to the rear output shaft to visually inspect with a camera but nothing seen there. I've pulled the transmission filters and they're in good shape. Same fine metal particulate but nothing large enough to be caught by the filter by the naked eye.
To eliminate an axle/diff issue I put the truck on 4 stands and worked it through the gears. It's the same as above. 1st gear allows everything to operate as it should but going to any gear results in the transferase locking up immediately and stop turning the wheels.
Other thoughts and notes to consider:
Yes, the brakes have been verified to release.
Yes, the vehicle rolls free with the engine off and brakes released.
No codes on the gear selector.
New batteries and good power connections.
"Mode" causes no change.
I'm leaning towards swapping the transmission/transfer case unit as a whole for all the reasons listed above but it's worth trying other ideas in the mean time.
The transmission fluid smells burned, obviously not good, and some fine metal particulate attracted by the pan plug and filter. No large chunks or notable pieces of things. I've drained the fluid and rinsed with 10w to see if anything else would be flushed out but nothing notable. Oddly, when I started the truck it went into reverse and moved about 20 feet before coming to an abrupt stop. I was unable to replicate this and assume a pocket of air finally filled somewhere and something locked up being the issue here.
I've pulled the plate next to the rear output shaft to visually inspect with a camera but nothing seen there. I've pulled the transmission filters and they're in good shape. Same fine metal particulate but nothing large enough to be caught by the filter by the naked eye.
To eliminate an axle/diff issue I put the truck on 4 stands and worked it through the gears. It's the same as above. 1st gear allows everything to operate as it should but going to any gear results in the transferase locking up immediately and stop turning the wheels.
Other thoughts and notes to consider:
Yes, the brakes have been verified to release.
Yes, the vehicle rolls free with the engine off and brakes released.
No codes on the gear selector.
New batteries and good power connections.
"Mode" causes no change.
I'm leaning towards swapping the transmission/transfer case unit as a whole for all the reasons listed above but it's worth trying other ideas in the mean time.
