I have a 93 F Super Duty/450 460 gas with 5spd, Dana 80 5.13. The spider gears have broke and damaged the ring gear. My question. I will be rebuilding this should i put a higher gear in like 4.30. Would i lose much low end. Truck pulls a 12k trailer Has anyone done this swap and with what kind of results in performance. 4.88 4.63 are also available. Looking for less RPM at Highway speeds. Thanks, for any input.

 

I too have an F-SD with 5.13s. Yes, it's really low, but I do a lot of hauling and like the gearing. By comparison, I also have an F-350 with 4.10s, and the 5.13s are like shifting all the gears down one: 2nd. in the F-SD is almost as low as 1st. in the F-350.
You can calculate it all out...
Take the current RPM at highway speed, and what you'd like the RPM to be, and see what percentage of a change that is. Now take 5.13, reduce it by that percentage, and you have the new ratio.
For example, at 55mph, my F-SD is at about 2200 RPM. If I wanted it to be at 1800 RPM at the same speed, I take 1800, divide by 2200, and that gives me .818, then multiply that by 5.13, and I get the new ratio. 4.19. 4.10s would get me real close...

 

If I remember correctly, for anything lower than 4.63 you need a carrier change. Parts for the real Dana 80 (what you have) are expensive. Your best bet may be hitting up the scrap yards and looking for one that already has the 4.63 gears (they were a factory option) and get the whole axle.


ON EDIT:
No you wont loose much by going with the 4.63, used to have an 88 F-SuperDuty with the 460 ZF5 4.63 combo, with the way that it was set up 13,000 lbs was about it's lightest weight (it was a welding rig). We never had a problem pulling, couple of times had issues stopping the load, but pulling it was never a problem.

 

Yeah, 5.13 & 4.63 were the main ratios, and as RJJP said, parts are pricey...
When looking at bone yards, you need to have the VSS in the axle for the speedo, so you're looking for '92-'97 F-Super Dutys...

 

I think the open carrier will take a 4.30gear. Also available is a 4.11 trimmed to fit. The 5.13 is a good puller no doubt. At 55 MPH with 30.5 in tires engine will turn 1980rpm with 4.30, 2163rpm with 4.63, 2247rpm with 4.88, 2362rpm with 5.13 . Parts availability is good for this axle.I am having trouble finding Technical info for rebuilding procedures for this specific axle.

 

PM me with your email & I'll send you a .PDF...

 

Make sure you're looking for the Ford Dana 80, not the Dodge "Dana 80" the dodge was a hybrid. From what I've herd. Plus the physical size of what dodge claims to be a Dana 80 is about as big as a 10.25.