89 Cherokee 4x4 won't engage on the fly

It sounds as if you have a clutch that is not disengaging all the way. Did you get the clutch replaced at the same time that you had the slave cylinder done? Did you get the master cylinder replaced too? If not, then you really had only half of the job done, and this is not necessarily the fault of "the idiot who is supposed to know better".

Earle

You are describing badly adjusted linkage I think.

The linkage under is open to the weather and needs some lubrication now and then, but when the tranny and t-case were removed for the slave job, the 'mechanic' obviously forgot or didn't know how to set the gear lever back up it would appear.

The adjustment isn't hard, but... It really shouldn't have gone out of adjustment. That implies he forgot to tighten down the tranny mount or didn't set the tranny square with the vehicle when he did tighten it down. I would verify the tranny is in straight and tight first which could be the cause before adjust the linkage or 'symptom'.

I would visually inspect the mount to make sure the bolts are tight and to see if the nut marks or washer marks seem to be different than the old marks.

If that is ok, then to adjust the shifter, you put it in 4 low. There is a stop there inside under the boot and you want 1/8" space to the stop. An 1/8" drill bit can be used as a measured spacer. You then go under the vehicle and loosen the one bolt on the shift rod so you can move the tranny lever so it locks into 4 low. Then tighten the bolt back up. This should set the 4 high in the correct place.

Mike