?have to hold the turn signal lever up until it starts flashing but then I can let it go.?
When letting go the turn signal lever, holds the position, and bulb continues to flash..?... Turn the wheel it cancels, it's working.
Holding and waiting you are just seeing the time it is taking for the circuit to heat the flasher.
Set the signal and forget, by the time you are ready to make your move it will be flashing
These are what ifs:
You could replace the flasher may or may not help, cut the delay.
The contacts of the signal switch could be dirty, because of none usage (truck not driven) . Put a few miles on it using the sigals and it will take care of itself.
Maybe the last owner only made LH turns, the RH not being used the contacts are a little dirty, again driving will help
Happy motoring drive and enjoy the truck. That was fun