So I am pretty sure my new truck has 3.73 (and needs an upgrade)
How am I supposed to tell when my door tag looks like this?

Click to zoom!

On my last truck, F250HD, there was a code under AXLE and I was able to tell that it had 4:10 gears. What is up with this? Any other way to tell?

 

There should be one on the rear end also. Sometimes you can tell by the door sticker but not on mine. Someone will chime in on how to tell that way.

 

Do you mean another door tag? Or do you mean crawl under and look at the pumpkin?

 

https://www.ford-trucks.com/forums/6...ild-sheet.html

 

If you stop at your local dealer, go to the service counter and ask for an OASIS report. Give them your VIN and they'll pull it and print it out for you. One page is a rough build sheet of some options, colors, engine, trans, and axle, and then the rest are all the dealer performed service items done to it.

This way you can find out if it's a limited slip or not too.

Normally, I believe code C1 is a 3.73 limited slip whereas a code 31 is a non-limited slip.

 

Crawl under and look at the banjo.

 

yea, crap, the truck is at my buddy's shop, 10 miles away, I was out there tonight but it is like 10 degrees out or some crap. I snapped a picture of the door tag with my cell thinking that the code must be on there, meh. I doesn't matter anyway. With all the upgrades I am doing right now I don't have an extra $1K+ to do the gears. When I do get around to doing the gears I want lockers anyway (more coin)

 

gr8scoot72 posted a couple years back: stock tire at 65 mph you should have over 2K rpms on 4:30 gears and under 2K with 3:73. Helped me. Hope it help you for now.

 

good to know, thanks

 

Mine is dead on 2k rpm's at 65 mph with 3.7's.