Hello,

1997 Ford F250HD 5.8L V8 351W. This is a regular cab long bed.

I am trying to read the tag and I don't know what it means. I looked online and there is some conflicting data. It think that I have a 4.10 limited slip differential.

According to the pictures, I see S131N on the top. However, according to this site, when I search by the top number it isn't listed as a 4.10 gearing: Ford Rear Axle Assembly Identification - Page 10 - FORDification.com

If you have any additional information to add to this, I am all ears. I'm running 35's on it so I am thinking of regearing to a 4.88.

 

You will have to take that off and clean it up to see all the numbers. What is the axle code on the drivers door pillar?

 

The door pillar was painted over. Can't see it.

 

If you remove that one bolt that the tag is under it won't cause a leak.
But even without that the tag seems to indicate it's got 4.10 gears.... the only other factory option was 3.55 I think.
Have you recalibrated the speedo for the 35's? The truck should do OK if it has 4.10's.

 

From the decoder ring.

S131N Ford F250 Pickup 85-98 over 8500 GVW
Ford F350 Pickup 93-96 3.55 10.25 L


https://www.fordification.com/tech/rearends_ford10.htm