rear axel
 

Alright, i just bought a 40HP fuel pin, noticed a huge difference, originally truck would start vibrating @ 73MPH. Now it gets up to 76MPH and it is very smooth for a first gen at least... if you have one you know what i'm talkin about!

my point is, it will not go any faster than that, my grandpa says it is because it has a low rear end?

Anyone else with a 1st gen dually have that problem, and nows how to fix it?:argh:

That's pretty much the top speed of all 1st gens buddy!Three speed trucks came with 3.07 gears,Overdrive trucks 3.54,I think 4.10 was optional.If you crank the pump it'll go faster!I got the three speed w/3.07's,and I am gonna put a 4 spd auto in it so I can keep up with the Hondas w/o revving the piss out of it.:choochoo:

if you turn the pump up and have a stock turbo you better get an EGT gauge cause at that speed the turbo is putting out nothing but heat cause your truck isnt intercooled.....

Yeah, remove the high idle screw and put a 3200 RPM spring in. You will be AMAZED at the difference. And logan nailed the gauges

my dad's 91 is a 3 speed, an option for the gearing issue is a Gear Vendors O/D unit on the tailshaft of the trans. I know they're not cheap but they work GOOD and will live up to a ton of power.

when we set up his '00 as the main service truck, he wants a GV behind the NV4500 to help out with the 4.10 gears!