I have a 05 SD 5.4L, 3.73L 4x4
So how do I know if I have a ford 10.5'', or Dana 80, or Dana 135.
I am guessing I have the 10.5'' and a 4.10 would have the Dana 80 but i'm not sure...

 

You'll have the Ford unit, the others are typically found in dually's, 450's, 550's etc.

 

Dana 60 in front btw aswell...

 

You have a Ford 10.5" rear axle with the stock limited slip in it. The D80 comes in 350 DRWs, the D135 comes in 450s.

The gearing ratio is largely independent from the axle housing. The axle housing limits the size of the carrier/ ring gear in the diff, which can come in a variety of tooth/pinion combos to set the gearing. The ring gear size for the Ford 10.25"/10.5" axles are self explanatory. The D60 rear is somewhere in the area of 9.75", and I'm pretty sure the D135 is somewhere around 14.xx"

The 10.5" axle can be geared from 3.55 to 5:38, you just have to swap in different carriers at some point in there. The deeper the gearing you go to, the more problems you have with breaking teeth, breaking ring gears, and in general breaking everything while backing up, driving loaded, running massive tires, etc.


Edit: I really don't remember when/why/how the D110 and D135 got switched up in the DRW stuff. Someone who owns one can talk about that I guess

 

These guys have you covered, but just so you know where to find this stuff yourself, your equipment specifications can be found here:

https://www.fleet.ford.com/truckbbas...essd-exlbb.pdf

And your gear ratio code can be found here:
https://www.ford-trucks.com/forums/s...42&postcount=9

All this comes from the tech folder sticky at the top of this forum.

 

thanks for all the help guys!