OK, so my 4wd was not engaging and I assumed it was a faulty vacuum motor, install new one still won,t work, install new vaccum switch. nothing. Discover my rt front bearing is shot and wheel wobbles assume this is causing alignment issues install new hub assy., 4wd still wont work. take apart and reassemble (found one shift pad off) works fine with truck jacked up, go for test drive, engeges and disengages properly for 100' down the driveway and quits working. repeat above except this time put washer behind fork to prevent it going back as far when in 2wd. test on jacks all ok. test drive all ok for 3 or four cycles and quits again 150' down the driveway.

Really driving me crazy. any ideas appreciated. pacmule

 

OK, I tore the vaccum motor apart again and added another washer, now I am holding it back about 3/16" from its full 2wd position. tested on jacks all good, no interferance. road test good for awile then started to get harder to engage but if I play with it a bit(rolling, turn steering wheel back and forth, ect.) i can get it to engage.

this is not ideal but the best I have had in a while so I am going to leave it then will test again in a few days after I put some miles on it in 2wd.

pacmule.

 

Some worn parts , just need to either find the right bad part , or just keep the economy going like you have , swapping parts till its fixed.
Are you finding any slug , dirt , rust in there ?
Its comin with anything that has shift forks , trans , 2 spd diffs , ect. , that the fork wears , or the lube sleeve falls off [ falls off , into where ] & shiftling gets bad , also good vacuum at the motor .

 

i realize u replaced the vacuum motor...but did u plug the vacuum leaks everywhere?..trace all the vacuum lines and you may find a loose line or a bad connection...favorite one is near the big line running from the vacuum to the boster and the little "t" line branching off that...next favorite is the two lines that hook up to the actuator right on the axle...passenger side front axle right on top of it...two lines..i had a loose connection there and lots of rust...

keep us posted