My buddy has a 2005 fx4 with 373's. I have a 2001 4x4 lariat with 355's. He is getting 488's installed in his due to lift kits and huge tires.Mine will stay stock looking no lift no bigger tires. Will his 373's fit on my truck?Are the rear end sizes the same on both trucks?Also does anyone know the number codes on the door panels to tell what type of gears you have?I seen a list somewhere on this site but have not found it in a while.Thanks for any professional help..

 

Can't really tell you if your gears will swap or not, but here's a list of the axle codes. Get the number form the door jamb sticker under the designation "axle" and match it here.
xle Codes

non-limited slip

X27 – 3:31
X19 – 3:55
X26 – 3:73
X25 – 4:10

limited slip

H9 – 3:55
B6 – 3:73
B5 – 4:10
Good luck with the rest.--DIY

 

Thank you very much for that information.I like your scab alot, i had a 98 just like yours but it was black. I rolled it 3 weeks ago and thats how i got the screw lariat.

 

I found a 19 under where it says axle but i never seen any letters.Im assuming that means 355 open.

 

Thanks a lot for the compliments. My truck may be old, but it's the only one I have. Yup sounds like 3.55 open gears, which is what you thought you had. I'll be interested to see if somebody else can tell you whether those gears will swap.--DIY

 

I was hoping someone else could tell me if they would fit to.I thank you for your info though.

 

Depends on the vehicles. All F150s have an 8.8" front diff. 4.6 engined have an 8.8" rear. 5.4 engined have a 9.75" rear. I believe the 7700lb(pre 04)/8200lb (04 up) trucks have a 10.25" rear. Now across model year, pre 04 and 04 up, I am not sure if there is any difference in the setup. Sme size gears and all, just not sure of any difference in the housing etc.

 

that's almost right. if it has a 5.4 it has a 9.75 regardless. if its a v-6 i would say it ALMOST definitely has a 8.8 unless special ordered. a 4.6 can have either. that is for the older trucks,04 and up i don't know what they have

 

get under both trucks and read the tags that are on a bolt that holds the cover in place. if you find 88 or 975 on BOTH tags then the gears will swap.

 

I should have added that both trucks have 5.4 engines.I will have to check those numbers out.My mech told me that it may not be worth paying him the 500-600 dollars to only step up from my 3.55s to the 3.73s.He also took into consideration that the gears would be free.MY main concern is for pulling a trailer thats going to be about 7500 pounds loaded. Im thinking any step up would make for easier towing. Any thoughts?

 

I think your mech is right. Thats not a big enough jump for you to even notice a difference. I would AT LEAST jump to a 4:10 or bigger for it to be worth the trouble.

 

I agree, alot of work for such a small jump