so my truck is a 5.0 with the AOD trans. i pretty much know what i have mechanically but one thing i really have no knowledge in is the axle and the gearing. its 2wd, and the axle code is 19, which i looked it up and that translates to 3.55 ford 3800#, locking. i thinking the locking refers to the wheels. because when i get stuck or something or have no traction, only one wheel spins. not both. so my question is are those good gears to have? bear in mind i rarely drive on the highway and its a street truck with a beefed up motor and trans. and what would the best gears be for a truck like that?

 

Axle code 19 signifies a 3.55 open(non-locking) differential which is a 1-wheel-peel like you describe, and that gear ratio is an OK compromise between power and efficiency for the 5.0 truck. But it's far from the ideal from a performance standpoint.. that starts with about 4.10 gears and goes up numerically from there depending upon the tire size and performance level of the engine.

 

yeaa my motor is semi built, along with the trans. but i think it really is held back by the gearing. im not 100% certain of my tire size, (came with the rims i bought) but they are big enough that i get tire rub in the front when the steering wheel is turned all the way in either direction. would 3.73 gears make a big difference over the 3.55's?

 

355 to 373 would be a small jump, slightly noticeable. I would recommend 410 gears to notice the improvement, and 456 gears to put on an impressive smoke show.

 

you should go check the tire size,otherwise we'd all just be guessing with you.
and of course state if you'll be sticking with this tire size or not.

 

if i go with 4:10's will i lose any fuel mileage?

 

Depends if you change your driving habits. It'll take less work to get to the desired speed, and around town that's a plus. On highway you may gain/lose/stay the same depending at what speeds you drive and what the engine rpm is at. With lower gears, you will be able to stay in OD up grades and in the engines power band

 

i think that would work great. i really only drive around town with it anyways. but one more thing, when it comes to the swap, do you just take out the guts and switch the gears? or should i just go for another axle all ready to go?

 

It would be easiest to swap the entire axle with another used one. The problem you'll have is finding a used 8.8" rear with 4.10 gears (assuming you have an F150?). I've seen 3.73's but never any factory 4.10's. You can buy a new set of Ford Racing 4.10 gears fairly cheap (~$140) from any Mustang or Ford Performance website, but you should really get the install kit and new bearings as well. It's possible to perform a DIY gear swap, but you need to know what you're doing and have somewhat special tools to get the clearances and tooth pattern set properly. Otherwise, you'll have issues with gear noise & wear. Obviously since you ask, you've probably never done it before, so I would recommend taking it to a shop with experience. A good shop will guarantee their work and will fix it if you end up having gear whine or noise. Typical cost for install should be between $250 to $400. All said, I would estimate total cost around maybe $600 to $700. You might find a good used 8.8" in a J/Y with 3.73 gears (maybe even a T-Loc)for less, so you might reconsider going with 3.73's.

To be honest, 3.55's are not terrible (as opposed to 3.08's) and even 3.73's would make a good street gear. It all depends on how tall (not wide) your tires are, the torque range of the motor, how much your truck weighs and whether your torque converter is stock or not. If you can afford it, going with new 4.10's and bearings and a professional install would be the best over-all route for dependability, liability and performance, IMO.

 

Ford trucks never came with 3.73 gears....

IIRC, explorers MIGHT have came with them stock, and they use the 8.8" ring and gear....

I agree, 4.10's in a f-150 is a needle in a haystack.....

Just bit of info with looking four a jy rearend,

If the axle code is, say a 19, like yours, it's a open differential from the factory....Now, if it were a H19.....That is a factory limited slip differential, 3.55 gears....

A letter preceding the axle code means limited slip; on the door jamb sticker....

Actual axle tags will read 355 for a open wheel 3.55 ratio, or 3L55 for a locking differential....or 410, or 4L10, etc, etc....

 

hmmm.. thats alot to take in, im wondering, how exactly does tire size affect power and gearing and all that

 

The bigger the circumference of the tire, the lower the gear ratio (Numerically higher) needed to turn it, and be the same as the original gears/tires....


33" tires....A 4.10, or a 4.56 gear set would put you pretty close to the original RPM's, etc....Therefore saving fuel mileage*

*-To a point.....Depending on your driving habits, etc...