i've got a 96 F350 4:10gears 4x4 5speed.at 70mph the tach reads 2400/2450 rpm in overdrive.which is the same as my 97 460 f350 E4OD 4:10's 4x4.iwas told the the diesel has a higher overdrive than the gas ??the 96 is bone stock with a new IDM(which ford was very proud of). and if the diesel has a better O.D. gear why the same reading ???

 

Not sure about your info on the comparison, but, my 96 with 410s as well as most threads I have seen on this topic in this forum say you are right on with where it should be: 70 mph at 2450rpm.

 

That's about right. The OD gear in an E4OD(at least a diesel version, not sure if they're different) is .71 I believe and the 5 speed is .76. That is for a ZF S5-42. In that 96 you may have a 47 but I dunno. It will still have a different OD gear than the E4OD and put your RPMs higher.
My truck with 4.10s and E4OD was around 21-2200 rpms @ 70 mph. Now that I have a 5 speed it is up to 24-2500 @ 70 . I drive 70 A LOT and it took my mileage from 20-22 down to 15.

 

not sure on the tranny 42 or 47 will have to look.all i know is the diesel get's twice the mileage as the 460 pulling the 303.5 cat.and it doesn't even know that the small line concrete pump is even there!with the cat on the back i get about 13mpg emptyor with the pump is around 14/16mpg