1999 Blazer with NP 233 3-button with auto trans
Bought the truck and no 4x4.
Connected vacuum hose to actuator under battery, no 4x4.
Replaced rotted vacuum lines, now have 4hi but no 4lo
Replaced dash switch, still no 4lo
Replaced encoder motor, have 4lo and 4hi with a little wiggle of the trans shifter it will go into and out of 4lo (assuming shift linkage is a little off).

I bought a Doorman 600-900 from a forum member new. It arrived Sat afternoon. I had tried to pull the encoder motor before but ran into the drive shaft yoke not allowing it to come out. The guy who sold me the encored motor sent me a link to a youtube video about pulling the front drive shaft.

I marked the yoke and drive shaft and also the diff and u-joint for placement. Removed the 4 bolts at the diff off the u-joint and set the front of the drive shaft on the exhaust. Took a 2x4 block of wood and tapped it on the yoke forward to move the yoke on the t-case shaft enough to get the encoder motor out. I tapped it a little too far and the whole drive shaft came off, so I'm glad I marked the positions.

Removed the encoder motor with a 10mm socket and wrench and an 8mm for the plug screw. Cleaned up the area and reinstalled the encoder motor and got the drive shaft realigned. Put the bolts back in for the u-joint. I forgot to tape up the caps on the u-joint that hold all the needle bearings in. One was slipping off, so I got a c-clamp and clamped it all back together and bolted the u-joint back in place.

Went to test the shift motor, and noticed it wouldn't go into 4lo still until I wiggled the trans shifter on the steering column. Probably a loose shift linkage, but for now, it works for me!

I was a greasy, sweaty, bloody mess, so no pics, sorry! Need to go wheel and test out the 4lo now!