Ok, wierd questions. 95 blazer 4 door, 4 speed auto, pushbutton 4wd.
1st 4wd not working. Think its vacuum line issue. sometimes in normal driving, highway speeds, when letting off the gas it sounds like its trying to engage the 4wd. if I raise the hood and jiggle the hose where it attaches to the vacuum tank, the sound/grinding go away for a while, but I know it'll happen again. what is it doing? And will new vacuum lines fix it?

2nd question. at 45-55 mph. Driving in 4th or overdrive, it slips out of fourth. if I hit the gas rpms go up, it grabs 3rd, and then shifts to 4th again, or rpms drop and it grabs 4th. if it was a stickshift, I'd think clutch was slipping, but its auto. and if I run 65-70 mph, no problems. what is it doing, why, and is my transmission dying?

 

*Moving to a new post of your own* - Instead of piggy backing off of an informational post for technical assistance.

4wd related problems are rather prevalent around here, but are also rather well documented in the Tech Article (DIY) section so start there. The clicking issue is covered in there as well.

The 45-55mph experience you have been having sounds like the torque converter coming out of lock up. To test that theory, next time it happens, try lightly pressing on the brake only enough to activate the brake lights, but not enough to change your speed. If the RPMs rise even more, but not really enough to drop you all the way down into 3rd gear, then the torque converter lockup is going screwy and you may be in need of a new torque converter.

 

Ok, diagnosis, and more questions. week ago, before 200 mile one way trip, checked fluids, was ok, then one week later, return trip, starts slipping out of overdrive as mentioned. turns out was 2.5 quarts low, had leaked at dipstick. so now that its full again, still leaking. trans shop says 550 to replace broken dipstick/filler tube and re-seal trans and xfer case. but I explained how low it was, and slipping and they said full rebuild with bands, and quoted 1800.
so... now what? reseal or rebuild? I'm already in for new motor, new computer, and partial repaint, is this thing worth it?

 

Oh, and vacuum lines were culprit with grinding noise while slowing, 10 bucks worth of lines fixed that. trans doesn't seem to be slipping now, but how big a chance am I taking just to reseal it and fix the leaks instead of rebuilding it.