Rear end ratio

[akcowboy]

I'm getting ready to buy a 1970 F250 and am curious about the gear ratio. I can't get to the Vin numbers any time soon and hope that someone can help out. It has a 360 and a 4 speed, is two wheel drive and spins 2000 rpm at 50mph. I beleive it has the 10-bolt Dana 60, it'd be really nice to know if i have 3.73 or 4.10 gears. I was told it got 15mpg but don't really think so. Also, what's the highest gear (for fuel economy) that i could put in a dana 60? Thanks for all the help.

[68F250]

Let's see, with a 31" tire a 3.73 @ 2K is 49.5mph.

Really need to know the tire diameter to nail it.

[akcowboy]

Sorry, it was late The tire is 285/65R16. How hard would it be to change to something like a 3.50 then?

[68F250]

Ok, looks like a 285/65R16 tire is 30.6" tall. So that would make 48.8 mph @ 2000 rpm with a 3.73. Going to a 3.54 will bump it up to 51.4 mph.

Sorry I've never opened up a Dana so I can't tell ya.

[akcowboy]

Thanks for the help! Where did you get that information? It's be really nice to have it on hand.

[heep70]

You got the tools to set up R&Ps? If not, then you should have someone else that does have the tool set it up with the proper specs. As far as taking them apart they are easy. A speader is nice to have if not a rubber mallet works.

[akcowboy]

I wouldn't put it back together, too much riding on it. We have a nice transmission/driveline shop that i would have do it, while i watched and learned of course.

[68F250]

I've collected tire size info from several places over the years and put them all in a big Word file. For the rpm/mph/gear ratio stuff I just use one of the many calculators on the net.