Tranny question on a 1 ton dually

[ole school]

I have a 68 1 ton dually im wanting to use as a hauler for my show truck. it doesnt do well on the interstate because of either the rear end ratio. or the tranny. most call the tranny a granny 4 speed. im looking for an idea to keep it a hauler but make it better on the interstate. i really dont want an automatic. Thanks for any help..

[Yukon Jack]

Gear Vendors has an add on overdrive that might be good, your other options would be to regear or go with a newer overdrive tranny.

Regearing would be cheapest but you'd have to be careful to still have enough gear to get going and handle hills. If money isn't a big issue, the Gear Vendor would be a great option.

[Longhorn Man]

you should have the eaton HO72 in that, id if it is all original, the 5.13 gear came with the daul rear wheel option.
You can locate a 4.10 gear in just about any 3/4 ton or one ton single rear wheel that has a small block and an automatic (unless otherwise optioned). That's prpobably the best gear you'll ever locate for that rear end.
This would cut your RPMs down quite a bit, but they'll still be 'up there' a bit.
The swap is easy, and no special tools at all. You just drop the whole center section out (from the front of the axle) after pulling the drive shaft, and the axle shafts.
Be carefull... it is about a hundred pounds.
However, you'd be better off locating a whole rear end out of a later truck. The drums for your set up were discontinued about 20 years ago, and getting replacements means junk yard trips.

[72truckman]

Early NV4500's out of 1992- 1995 C/K2500's and 3500's have a 6.34 granny first and a .75 overdrive