Help! New transmission, same problem

[Bf4045]

Please help before I drive this thing into the lake! 2002 Dodge Ram 1500, 4.7l, 4x4. Old transmission was causing problems. Trusted buddy, who is much smarter than me, finds a used transmission at junkyard, $250. Figure it's easier to replace at that price than to attempt to diagnose and throw money at parts. Big mistake...new (well, used anyways) tranny is doing nearly exact same thing as previous tranny: 1st and 2nd gear seem to do fine, but once it warms up after driving a bit, then hits third gear, it stays in third. My buddy called it "limp mode". No slipping, mild "clunk" from second to third, and that is it. It is reading codes P0770 shift solenoid e malfunction, P0988 transmission fluid pressure sensor/switch e circuit range, P0734 gear 4 incorrect ratio. I took it to a mechanic who said the solenoid pack needs replaced. I took it to another mechanic who thought it odd that both old and new tranny were having nearly identical issues and said it was likely the transmission control module. Man, I'm already in the poor house and really don't want to start throwing money at parts! I know that's alot....any.thoughts?

 

[HemiLonestar]

If the newer trans was known to be good (you take your chances with junkers), then it would point to software to me. I mean, it is possible they both were junk, but it smells electrical to me.