I recently swapped a 4l80e into my 2006 silverado SS , and it only has 2nd and reverse. I swapped the brown and white wire on the plug and i added the front speed sensor to the computer, and then we used HP tuners and loaded the tune from a 2006 silverado 2500 6.0/4l80 into my computer and then tuned it from there we even tried two different 2500 tunes, but the problem is still there

There are two codes that come up, they are shift solenoid b malfunction and shift solenoid a malfunction. I had both of the solenoids replaced, but the codes are still there and it is still stuck in 2nd

Any help would be greatly appreciated!

 

With a second gear start condition your trans is in limp mode. Basically both shift solenoids are off so this is why in forward you only have second gear. The first thing I would check is to make sure you have power at the trans.

 

What stall speed torque converter did you install? Did you tune for it? There are a couple of DTC's that need disabled with a higher stall converter. Basically, if the pcm doesn't see the rpm drop when it upshifts, it thinks the transmission did not complete the shift properly(hence the shift solenoid codes), and defaults the transmission into "limp mode".