Normally the 3rd gear direct drum will easily lift off of the input shaft, this one is stuck for some reason.
This is not a magic trick, the drum should fall off when tipped like this.
Here's why, the 3rd gear clutch teeth have mysteriously worn through the input shaft hub. This destroyed input shaft is now a wall decoration.
Remove the drum, snap ring, and clutch pack assembly. Blued steel is great for gun barrels, not for clutch pack steel plates.
The friction lining is completely worn away on this 3rd gear clutch plate, in fact, the plate's inner steel core is worn through in places and several teeth are missing. I've never seen one quite this bad, ever!
Coned clutches are bad, bare metal is bad, this 3rd gear clutch pack is completely shot, no wonder the truck would barely move!
Moving back to the overdrive housing, remove the small diameter wire snap ring and the overdrive brake clutch pack.
This clutch is well worn and near failure as well, steel showing on the friction plate is not a good sign.
After removing the two lowest snap rings at the bottom of the clutch pack, (1) waved and (1) flat, remove the outer T-25 torx screws on the side of the OD case to access the retaining snap ring. Open the snap ring and remove the whole assembly. Next using a press or home-made contraption, compress the 820# spring and remove two snap rings to complete disassembly of the overdrive components.
This build will incorporate a billet output shaft so the stock shaft was removed.
All torn down:
