Rear Axle: Champ Truck Diff

[kamzack]

Is there a simple diff swap for the T Cab. Want something around 3:31, 3:58 range. Won't be used for hauling or towing, just fast driving.
Thanks in advance,
Kim

[Warren Webb]

1/2 or 3/4 ton? Half tons use the Dana 44 rear. I don't know if the splines are the same count as on the cars but if they are it shouldn't be a problem just swapping out the gearset. The axle housing itself is wider so the assembly from a car would not fit properly as would the axle shafts themselves.

[kamzack]

1/2 ton short bed, soon to be 259 with overdrive. Knew it was wider and wasn't sure if car 44 gear set would swap out. That would be the easiest. and thanks.

[Starlight]

Kamzack....Yes, the car gears will swap out, had mine done 3 years ago.....From 410 to 354......Keep on Studebakering

[kamzack]

How did it affect Power, rpms at speed, will it still haul or pull a reasonable load? I know it will give up some of low end torque but again more interested in speed without engine being wound way too tight. I have a 62 Daytona with 259,331 gear and 3speed overdrive and gets 20mpg running 65 to 70.(for sale by the way to pay for Champ) That's what I'm kinda lookin for. I'd probably be best off with 354, so kinda on the hunt. for one or the other.
Thanks again,
Kim

[jackb]

I don't believe you can simply swap between a 3 vs. 4 carrier...?

[PackardV8]

Yes, the ratio break is 3.91, which means the entire carrier has to be swapped out, not just R&P.

What complicates the equation is not knowing the tire diameter kamzack is intending to run. A truck outfitted with wimpy 50 or 60-series 15" car tires has many more revs per mile than a true truck tire.

The 3.54 in overdrive is 2.53. Running car tires effectively increases the revs-per-mile and has the same effect as a lower gear ratio.

So, decide which tire will be on the truck, get the revs-per-mile and then gear for torque peak 2400 RPMs) at highest highway speed (75-80 MPH ?). With the 3.54 gear and overdrive:

A 215/75-15" truck tire is 27.7" tall is 728 revs-per-mile, or 2500 RPMs @ 80 MPH

A 205/50-15 car tire is 23.1" and 900 revs-per-mile, or 2500 RPMs @ 67 MPH.

So choose the tires before choosing the gear ratio. Just FWIW, OEM Studebaker 15" truck tires were in the 26.2"-26.6" diameter range.

jack vines

[kamzack]

Gonna try to find wider tire enabling using 225 or 235. thanks for the info.
Kim