pcart23

I just put some 35s on my 03 f150 4x4 supercrew 5.4L and i want to put some 4.56 gears and i was wondering which brand of gears i should get and how big the front and rear diff are. Also about how much did you pay to get your front and rear diff changed? Also anything i should look out for.

Thanks,
Paul

anthonykane6

Well i don't have 4wd,but when i put 35s on my truck and geared it to 4.56. I got my mpg back and more torque.

chad085

I have the same truck just supercab, not screw. You have a 8.8 IFS front axle and most likely a 9.75 rear. I think all screw's, especially 5.4 trucks used this rearend. I also have a 9.75. I can't remember which one is which, but i have precision gears in one diff and motive gears in the other. I was told by my local gear shop that neither company had applications for both axles. I also ditched the factory worn out LS for a detroit truetrac, and all together i spent about 2,000. This was about 2 years ago so the same service is most likely more now. I have had zero problems and been very happy with the install. The truetrac is all gear driven, so you don't need a friction modifier in your oil anymore.

This will put your rpm's just a little higher than stock when running 35's. My dad's stock '02 runs about 2000-2100 rpms in overdrive at 70 mph, my truck is about 2200-2300. One thing worth noting is that your speedo will be WAAAAAY off after installing the gears, so you will need some type of programmer to correct it. I remember driving home from the gear shop and laughing at how far off it was before i got home to reprogram.

pcart23

I have 3.73 gears in there right now. All i would have to do is change the ring and pionion right? i know its not that simple but thats all i have to do?

Thanks,
Paul

mikek2111987

whoa whoa whoa.
im new to the truck world, i know when i put 4.10s in my mustang my gas mileage and drive ability went down considerably. so if i put giant tires on my truck some day when i lift it, a larger gear ratio will infact better my MPG?

rplatt56

4.10s offer no better advantage over the 3.73s. If you are going to do a gear change go at least 4.56s. MPGs will improve a little this way. Now if you want sure power go 4.88sw but remember where all the gas stations are.

pcart23

Yea thats what im going to do but i was just curious if i only have to change the ring and pinon, i dont have to do anything else special?

Weldman0730

Yeah just the ring and pinion, unless you go with a LSD or a locker, or if you have one already then the answer may be diffrent.

pcart23

Im pretty sure my truck came stock with a 3.73 limited slip axle. So what would the differnt answer be?

thanks,
Paul

Weldman0730

well then you would still have to change the ring and pinion, but also at the same time it may be a good idea to put new clutch plates in the limited slip and you will also have to put oil in it W/ friction modifier(I think the LS from the factory uses clutch plates).

I guess its the same actually unless you want to rebuild the LS, and you must put a oil in there that wont mess up the LS, one with the friction modifier.