I need to swap diffs and I know mine is a 4.10 but I'm not sure on my spare and was hoping someone had a breakdown on the identification tags.

 

What do the tags say?

 

3 s-115 l
73 10 2 9b02

 

.....

 

Doesn't look familiar, but I'd have to guess that it's a 3.73 open 10.25" rear.

 

Hmmm well it is a 10.25 but I'm fairly certain it's a LS and 4.10.... Only because to get proper speedo correction for the tires I have to change gear ratio to 4.10 as well. Hmm

 

Any idea what the last 4 digits mean?

 

Correction, that's a limited slip 3.73, 10.25".

L 73 is 3.73 LS, 10 2 is 10.25".

 

If someone has previously monkey'd with the diff, then it is any body's guess. You can believe the 10.25 part I'm sure. But if you had to program as 4.10 then something aint right.

To be sure you can count the teeth on the pinion and the ring and do the math. Ring gear divided by the pinion=the ratio. If it comes up as 3.73 then your tires are way different diameter than stock.

 

I think he's talking about the tag on a spare axle he has, not the one in the truck. Would help if he would post the tag numbers from the one in the truck for comparison.

 

Thanx! I have 315 tires but i programmed it for that. I used gps to make sure my speed was correct and had to change gear ratio, I first tried 3.73 but it was still out so I bumped it up to 4.10 and its damn near bang on! Not sure why it would be like that I thought for sure it was 3.73 till then. I don't think anyone's changed gears being as how they should have done seals and bearings too but didn't! The only difference are the last 4 digits on both axles. I would post the tag from my spare if I could get ahold of it but I'm not at home until Sunday.

 

Usually when programming you use the circumference of the tire and it's usually gunna be a little smaller because of squish. Maybe try going to 3.73 gear ratio then entering in your circumference compensating for squish. Remember to get the mph as close to stock as possible, which is 2.5 mph faster then a gps for these MY trucks.
I believe the tag he is talking about is the one on your driver side door. It'll give you the axle code which will determine either LS or open diff and 3.55, 3.73, or 4.10.

 

No, I'm referring to the tag on the axle. However, the door jamb tag will tell you which ratio the truck came with from the factory.

So, the tag number you posted is the one on the axle in the truck now? Please post the axle code from the door tag to confirm.

The last 4 digits don't have anything to do with ratio, I'm not sure what they signify.

You also don't do a speedo correction to make the speedo agree 100% with the programmer - the speedo by design is a couple MPH high. What you do is tweak the settings till the programmer agrees with a GPS.

 

I don't have a doorjam sticker, bought it used. I programmed the circumference in with the values supplied by edge in the manual and with it programmed with 3.73 it was nearly 10km/hr slower then GPS. My spare diff tag is
3 s-115 L
L73 10 2 0L06

 

You are gunna want to get the speedo 4 km/h higher then your programmer. Also get your programmer the exact speed as gps. You may have to adjust your circumference more. I know I'm running 285/70/17 and with the adjusted circumference my programmer says I'm only running 31.5" tires. But my speedo is pretty dang close to stock.