D400 gearing

[jkeckley]

Hello,
I've got a 1970 d400. It runs great, has a 4 speed and single speed rear end. The problem is the top speed. It is wound tight at 45 mph. The rear axle is 6.20. If it would do 55, I could live with it. I've driven other big dodge trucks and none of them were geared this low! My other truck had a 6.80 rear and didn't seem geared that low. Did the np435 come with a lower 4th then 1:1? Something is strange about this truck.
I have a 5 spd out of a d500, but don't think it's an od model. Are there parts out there to change it over to an od unit?

[712edf]

The 435 has a 1:1 direct drive 4th gear. The NP540 was available with OD. Rare altogether & even rarer in a Dodge (if ever offered). Other makes used them & there are slight differences in them all.

My truck has 6.80 and doesn't like going 45.

Taller tires?

Bucky

[caseman]

Try 7,17 In my 76 D 600 / 2 speed rear 7.17 high -9.99 in Low /318-series 3 Engine + 5 Speed Straight [No OD ] 55-60 is no problem /All so have a C 800 361 ,5 speed 7.17 Rear end /no 2 speed /My old Flatbed -tiltbed Was 1970 D 500 318-4 speed + 2speed [ 5.80-8.10. ] Sure wish It was still running all ways Got 8.5 miles to the Gallon.