I suggest that as soon as you get your newly purchasing truck or blazer home, as soon as it's off the trailer, that you drop the tranny pan and change the filter & fluid. I would do this even tho the fluid shows that its full and that it smells okay (not burnt smell). I have had two trucks that would not hardly move at all but fluid looked okay.
After dropping pan and checking the filter, it was't filty or dirty, just that if you closely at the filter, you could see that it had formed a hardened film like (kinda like way gas will solidify in carburator over time). I think this is due to the vechile just sitting for months on end and never being cranked. Once changed, trans. shifted just like it should.
Along with that, I always change motor oil & filter and check the front & rear diff. and also check level in transfer case. This is cheap investment for what savings you can get in long run. YOU CAN BURN UP A TRANSMISSION VERY QUICKLY IF FLUID IS NOT FLOWING. I MEAN 2-3 MINUTES IF YOU START REVING IT UP JUST TO SEE IF YOU CAN GET IT TO MOVE 30 FEET.
I am sure most of you guys know all this but this it mainly directed to all these NEW MEMBERS that just got a mv or going to get one and may not know how quickly damage can occur. Also I would hate to remove tranny and have it rebuilt & find out that it was just stopped up filter. JUST DON'T ASSUME IT NEEDS REBUILDING WITHOUT CHECKING ALL DELTAILS CAREFULLY BEFORE YOU MAKE DECISION TO REMOVE IT.