Ok so i just did my 4.3 to 5.3 swap and i can already feel a difference, the only thing is that my trans is being really weird :/
It was fine on the 4.3 then when i swapped the 5.3 in it started acting up, when i put it in D it takes off in 3rd gear, so i have to manually shift to 2nd. I also have no O/D. I hooked up my scanner and i got these codes

P0463 Fuel sensor
P0713 Transmission Fluid Temperature Sensor Circuit High Input (which means?)
P0748 - Pressure Control Solenoid Electrical (what the hell is that?)
p0758 Solenoid Circuit B
p0785 shift timing solenoid malfunction
p1810 TFP Val Position SW Circuit Malfunction

Can this be fixed? Can this be caused by ground wires? Not enough fluids?

Anything? Also can someone tell me how many sensors go on the transmission? Its only 4 right?

 

Vroom

 

Did you happen to pinch a few wires somewhere like between the behousing? Or leave a ground off somewhere like on the back of the cylinder head? I can
check those codes for you later

 

P0713 means that the PCM thinks the transmission is overheating (rather, it means that it is short circuited and shouldn't be)

The other 700 codes mean that you have a wiring issue. Did you have to modify any harnesses, or did you swap PCMs, or did you pinch the harness at the back of the engine?

 

The P0748 is referring to the line pressure control solenoid, you may have an issue with the solenoid, or more than likely it's wiring, and the code may set under low voltage conditions caused by high electrical system demands, as stated here:

http://www.c-hock.com/downloads/gmfs/P0748.pdf

The info in that link is for an 02 Sierra, but I believe should be the same for you

 

No i checked that :/

No i checked the harness and its fine, and its a original harness with original pcm

Hmmm i need to check the solenoids, see because it works sometimes! I hate that it will work for like 4min then go into limp mode, even if i clear the codes its still in limp mode . Then my girlfriends dad added like two extra quarts of tranny fluid -_- lol so i need to drain it out, even though i doubt that could be it.
I need to check ign0 fuse, i have read that that could be it also, or my ignition switch, if i'm not getting power, or my converter :/ ahhh there's sooo many things and i just wanna drive my truck with out having to manually shift from second to third. It suck! then i have a exhaust leak so people wanna race lol but there's no point cause i don't go anywhere!

I might replace the filter and oil, idk