94 s10 blazer tahoe,transmission problems.

i have a 94 blazer s10 tahoe 4.3 v6 vortec.
the problems is.
when i put it in drive,it'll only go about 2 mph.
when i put it in 1st and 2nd gear it'll go only 15mhp at the most.:banghead:
it happen before.i put tranny luid in it and it ran fine,but its freezing ice outside at the moment and i just put fluid in it again and it wont go like it did before,mayb it needs to be warmed up so the fluid gets to it or somethings seriously wrong with the tranny... and another thing.the 4-wheel drive is a touch button,how do i know if the 4 wheel drive works or not?

For the tranny, start with a complete flush and change fluid, shouldnt take long at all for the pump to pick it up, are there any lights on the dash lit? For the 4-wheel drive, put it in 4-wheel and get in some grass or ice and spin the tires, and either have someone watch the wheels or get out and look at your marks, you will be able to tell what wheels are spinning just by looking at the ground.