How do I tell witch Diff is in my truck 97 4x4 HD ext cab with 4.10 gears and ltd slip. Need to replace the diff cover .

 

sterling 10.25

 

thanks for that I only want to buy one cover

 

Ford sells a nice one for SuperDuty (same rear). Finned aluminum and relatively inexpensive when I bought mine a number of years ago. Bolts right onto the OBS rear. You'll need to buy some new longer bolts as the originals aren't long enough due to the thicker flange on the aluminum cover. I am thinking mine was something like $29 - $39.
Of course aluminum has gone up since then, so I won't guess the price. Looks great! and a boatload cheaper than expensive aftermarket diff covers.
Can't remember the details, but I sure someone here remembers. Search diff cover and I am sure you'll find the thread.

Searched for ya. Here you go:
https://www.ford-trucks.com/forums/6...ver-cheap.html

 

I need to replace mine too. It has developed a small pinhole up towards the top and is wet with oil. Fordparts.com shows that cover to be $69.65 now. Might just be worth it though versus the $30 for a stamped steel unit. Anybody know how the aluminum ones hold up to road salt?

 

I ran one of these guys on my OBS with great results (and pulled it off before I sold it....saving it for my next OBS).

Ford Sterling Cover - Differential Covers - Spyntec Industries LLC.

They have a lifetime warranty and are pretty dang tough but they cost more than the OEM ford one. I bought mine when they had some sale for $35 or something crazy cheap

 

also another interesting read for diff cover strength
Differential Cover Test - The Great Diff Cover Shootout - Jp Magazine

 

That's awesome. I love their "Ahhh, screw science. Let's take 'em out and shoot guns at 'em" approach. Sounds like something I would do.