I found taking out the fill plug, taking out the stub and pouring through there. then have someone watch for when its full. Put plug back in and overfill 1 quart.

Quick question I am planning in changing the tranny oil on this truck its got the nv4500 just like mine. I am currently using amsoil on mine but was curious about the Mobil Delvac Synthetic Gear Oil 75W-90 will it work on it ?

synthetic motor oil works good

What?

Synthetic motor oil in a NV-4500 transmission? Im sorry but this is misinformation.

NO. you can ONLY run ams, RP, and castrol (also comes in dodge and gm bottles)

Specifically:

Redline's MTL, RP's Synchromax LT, Nissan's MTL, Honda MTL, Castrol Syntorq LT

Those would be the only acceptable fluids for the NV4500. Notice the "LT." Not the regular RP Synchromax. It has to be a full synthetic 75w-85w GL4 MTL. No substitutes.

and AMSOIL MTG "Formulated specifically for maximum protection in the most demanding manual transmission and transaxle applications where an extreme pressure GL-4 gear lube is specified, including those where high horsepower/high torque engines and towing or heavy loads increase transmission stress."

Yes, I forgot about the Amsoil.