o/d question

[914x4sport]

Ok so I put a new(read:used) tranny in my exploder and Ive noticed that when Ive been drivin some distance in o/d, at highway speeds, it occasionally will not reengage after shifting to drive(i.e. climbing...acceleration)Ill park it for a while(work,store...) Come out put it in o/d drive down the road and it shifts fine, drops into o/d when its supposed to and everything...When I picked up this tranny I noticed that the vaccuum adjustment knob on the side of the tranny had been turned and fiddled with by one of the guys at the place I got it..Could this affect the o/d? Also there are two(?) Square adjusment bolts on the side of the tranny that adjust the bands(?)Will adjusting those(which one) affect the performance of the o/d? Alot of questions I know...Also with that vaccuum valve would anyone be able to tell me where it should be set at?(I.E. # of full turns from either full up or full down positions)ALSO will having too much fluid in the system affect the o/d, cause it not to reangage? Just a few questions ..Thanks for any help at all..it would be much appreciated..