On my NV5600 I have one fast cooler on the drivers side and a genos filter on the passenger side. Driving at normal highway speeds 65/75 mph with no load the temp will run between 140 and 165 depending on the ambient air temp.
Pulling my 13,000 5th the temp will increase to 200/220 Deg. again depending on outside air temp.
My NV241HD with one fast cooler usually runs a little cooler but not by much, it must be the Amsoil motor oil I'm using in the transfer case.
The rear axle has a Mag-hytec cover with LE 607 for lube and normal unloaded crusing the temp runs about 150/160 deg. pulling the trailer and the temp jumps up to over 220/240 depending on out side air temps.
Terry