Need help on 94 burban

Hi everyone,
I am new to this forum and learning how to post this thread.
I have a problem with my 94 suburban and I can't solve it.Any
input would be greatly appreciated. When I come to a stop and
try to take off it feels as if the emergency brakes were engaged.
Once on the freeway and pickup speed, everything seems to be ok.
By the way as the truck picksup speed I don't feel the tranny shifting.
I have checked TPS,MAP,PCM,Catalytic converter,knock sensor, because I
thought it was an engine problem. All of that is ok. Now I believe that
the tranny is stuck on 3rd gear(limp mode). I am about to
replace the tranny, but before I do that I would like to get some input
from someone who has ran into this problem and was able to solve it.
Thanks everyone in advance for the help.