What transmission did Chevrolet put in their 1989 1500 silverados?

I have an 89 silverado 1500 350 V8 5.7 liter and 3rd gear in the transmission went out. I did some research and I'm pretty sure the transmission is a th400, but I just wanted to make sure and find out if there is any other transmission that would fit my engine.|||They put TH400 non OD transmissions and 700r4 overdrive transmissions in those.............md|||it,s either the 350 transmission or the 400. the 350 has the right corner cut off on the pan and has 13 bolts holes and the 400 has an electric downshift.|||If you want to know which transmission your truck uses, you can simply go to your GM dealer with your serial number of the truck %26amp; have them print off your truck options (RPO codes), including the type transmission you have.