Just did the 4l80e swap on my 00 Silverado. Took it on a 140 mile round trip. Kept smelling trans fluid. Trans temp was steady just over 160degrees. Got it home checked everything to find the vent tube wet and trans fluid on cross member.

 

Forgot to mention it shifted fine until I was about home. Then hard shifts from being a qrt low. Also I didn't swap out the neutral safety switches. Wouldn't think that'd cause it though.