I have a 2001 F-150 with the 5.4 Triton V8 and 3.55 gear ratio rear-end (non-LS). How can I tell if it is a 9.75" or 10.25" differential? Both are 12 bolt. I know that the 9.75" is standard for this generation of trucks, unless the 7700 lbs. axle option was chosen, but I bought the truck used and don't know about the original options chosen when it was first purchased. I do understand that the front is an 8.8".

Thanks for any help.

 

Look on the tag on the diff. It will have something like 9 75 or similar. Also, if you don't have 7 lug wheels, you don't have the 7700 and the 9.75 came with the 5.4.

 

Thanks for the prompt and helpful response, Kingfish. Since you're from the Free State, I guess I could have just driven the truck over for you to inspect.
Again, thanks.

 

The 10.25 was done around '99 anyway after being replaced with the 10.5 when the superduty series came out.

Ya got the 9.75 in yer F-150.

Adrianspeeder

 

Thanks, too, Adrianspeeder. It's good to have other forms of confirmation, like Kingfish's remarks about the 7 lug wheels, as it's too cold to be crawling around under the pumpkin looking for numbers.
I may swap up from 3.55 gears to 3.73 (am now running 265/75/16 tires). I have 4x4 - should I consider adding limited slip or a locker to the rear at that time? (I assume that I'll need to change up the front gears to 3.73, also, but think that adding ls/locker up front would be too much investment for the offroading that I do.)
Thanks.

 

A LS in the rear will help. I had one truck with out a LS and will not make that mistake again. With a LS, you may not even have to use 4X4 at times. A locker or LS up front may cause problems in the turns. The vehicle will have a tendency to continue to go straight. And yes you will have to do both front and rear gears. Front is an 8.8".

 

HI!... All 5.4 equipped F-150's came with the STERLING 9.75 rearend. All 4.6 equipped F-150's came with the 8.8 rearend. The 10.25 rearend never came in a standard F-150.

 

Thanks, guys. I didn't expect to get the A team weighing in with help for my inquiry. This is great.

Factory LS ok or should I look to aftermarket makers (Auburn, Eaton, etc.)? My offroading is for hunting, fishing, and some camping, not rock-crawling at Rubicon or in Moab (though some boat ramps would put up a strong challenge).

 

HI!... The factory limited slip is pretty strong. The LIGHTNING guys rund 10's on the stock L/S without breaking them. If you decide to upgrade it though, look at the DETROIT "TRUE TRAC". It is one of the better ones out there and is much stronger than the factory L/S.

 

Thanks, Neal, and Kingfish51, and Adrianspeeder. I feel pretty good about my planning with your helpful assistance. What a great community on this board!

p.s. to Kingfish51 - If you see a silver 2001 'Screw stuck on a boat ramp on Solomon's Island or in Chesapeake Beach, you'll know that I "Screwed-up."

 

Ford/Sterling, call it whatca want, all made in the same plant in detroit. Friend works on the line and I keep askin her to slip out a 10.5.

Never had a problem on the ramp with a stock LS.

Adrianspeeder

 

100% incorrect. F-150s with the 7700lb payload capacity received the Sterling 10.25 rear axle. For the 97-99 (2000??) model years, that truck was called the Light Duty F-250, later renamed as the F150/7700LB when the SuperDuties were redesigned. They were essentially an F-150 with a heavy duty rear axle, heavier rear springs, and 7-lug hubs, rotors, axles, and wheels.

Unless you have the heavy duty payload package, it's not the 10.25.

-Joe

 

HI!... I was 100% CORRECT!!!! If you read my post you'll see I said the "STANDARD" F-150. Not the F-150 7700, which is actually a F-250 for that time.

 

So because the 7700 lb package is an option, does that mean that the 5.4-equipped trucks are not 'standard' either? It wasn't a different model, just an option on it. That's standard in my book.

-Joe

 

HI!... Well let's see :

STANDARD 5.4 F-150 =

- 5 BOLT WHEELS
- 9.75 STERLING
- 4R70-W (98%)
- light duty springs
- No step side offered


F-250 5.4 - (F-150 7700# PACKAGE)

- 7 bolt rims
- 10.25 STERLING
- 4R-100
- HEAVY DUTY SPRINGS
- DIFFERENT BRAKES
Looks different to me. My book must be in colour..........