The Stovebolt Site Forums The Shop Area Driveline "Q"ford 250 full float rear end ratio? my GM 1 ton

Hi All, Seasons Greetings;

I have been pulling my hair out trying to determine the best rear end for my 1939 Chevy COE tow-truck hot rod project.
I am using a 1980 GMC P30 1 ton dully frame. No motor/trans/rear-end on frame yet.
I know I want tall highway gears on an 8 lug rear-end. I also need it to be as narrow as possible. I have been watching for, 64" width, GM 8 lug with 373 or higher gears. But so far no luck. Most are 68" width with 411 or lower gears.
So Friday I picked up a 1980's Ford rear-end, used on F.250 & F.350 trucks.10.25" 12 bolt rear-ed. 66" width, full floating, 8 lug rear-end. I like what I see except I really hate the name ford on it. I don't use ford parts on my Chevy's, but I need something now.
It is a 66" width, full floating rear-end & by doing the counting the tire rotation thing, I think the gear ratio is 3.46? Counting 10 tire turns, yoke went 17 & 3/4 turns. For calculations would that be 17.3 or 17.75?? 17.3 x 2= 346 & 17.75 x 2=355, which is it??
Both numbers sound good for HWY gears but I have not found any data helping me identify this rear-end. The tag has these #s, 2 V122C also 55 102 9L16 . On top of the pumpkin I found ETTW.AA also ford's logo. Hard to look further, it's still in the back of my trailer, tight fit with side boards. Can any one help me with the ratio. Also, what do you think about me using this ford rear-end, any other reasons beside the word ford on the casing?
I already know I will need to move the spring perches to match my GM springs. I think I can live with 66" width. I will be changing to air ride suspension. I want to use the front half of my main leaf's as part of the 4 link air ride? Does my ideas sound smart or not so smart???

Ford used a Spicer 50 in those years which was a very good rear end. They came in 3.54 and 4.11 ratio. Even though the 8 hole bolt pattern is the same as GM, you will have to use Ford wheels because they had a slightly larger hub than GM. Ford wheels will fit a GM, but GM won't fit a Ford. If you have the 3.54, you are lucky. The 4.11 was much more common.

Not for sure what the Q code is, but here's a link to Ford axle codes. You can also pull the pan off and count the teeth on your gears. If it's a 10.25 rearend, it's probably the Sterling full float. It's a pretty good rearend. The only drawback is that they have a weak pinion. It's not really a concern unless you'll be putting 40" tires on and rockcrawling.

http://www.ford-trucks.com/article/idx/0/022/article/Ford_Axle_Code_Chart_.html

Thank you both for your info. my rear end must be 3.54 ratio. It is a full floater. The ford web site really helps. I only wish mine had disc brakes. I will look for a set up.

For a disc brake setup, you may want to look at vans instead of trucks. If I'm not mistaken, Ford changed their truck bolt pattern in 98. Their still using the 8x6.5" on vans though.