What transmission do i have in my 1994 chevy truck?

i have a 94 chevy silverado truck with a 350 throttle body , 2 wheel drive and an automatic transmission . i've had the transmission rebuilt by coleman taylor a few years ago and its not under warranty anymore. i dont do much hauling , no more than a trailor every now and then. the trans is now not shifting right. when i first start driving the truck it shifts fine , but after the trans warms up , it seems to get stuck in 3rd or 4th gear.i know i have a 4 speed with overdrive , i've been told i have i either a 700r4, 4l60, or 4l60e transmission .can any1 help with this problem or at least let me know what kind of i have so i can buy a new one