Streetwiseguitar

With the mileage be noticeably worse with those gears?

OhioLariat

Mileage with 3.73's? You'll never notice the difference, unless you begin to enjoy the extra off-the-line performance, and start taking advantage of it.

Streetwiseguitar

Where would your suggest purchasing the gears (the least expensive outlet)?

OhioLariat

I'd get a complete rear end from a yard, like Jprevat suggested. It will be MUCH less expensive than having gears installed (which runs $1,000+ done right with a rebuild/bearing kit), and if you're at all mechanically inclined, the swap isn't hard to DIY. Afterward, you should be able to sell yours and recoup a little of the cost. If you're not going to do it this way, then I wouldn't bother.

EDIT: If using car-part.com, you'll need to search for a rear axle assembly for a '98. F150, as they don;t show anything better than 3.55 for a '97. You may also be able to upgrade to disc brakes. I think the only additional part needed is an e-brake cable. There've been a few threads on this subject.
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Streetwiseguitar

Ugh... I'm afraid I'm not that mechanically inclined. :-/ So, the '98 was using 3.73?

PerryB

I second doing a complete swap with a salvege yard axle assy. A 3.73 unit should be fairly easy to find.

Streetwiseguitar

Question : why go with salvage parts? Wouldn't they be terribly abused and used?

PerryB

If the axle assy. Is a rusted/corroded mess, I'd pass. Otherwise, if you find one of reasonable age and mileage its probably fine. Unless abused or badly neglected, it's a pretty durable item. I think you're missing the salient point though. Instead of completely disassembling your existing axle to re-gear it (lots of labor) just swap the whole thing out with one that has the desired gear ratio. WAY easier. An 8.8 axle in 3.73 should be fairly easy to find. -- Now after all that...... If your axle code is 19 (and it's never been altered) you have a 3.55 axle ratio. Swapping to 3.73 is only about a 6% reduction. Maybe not worth it to begin with. If you wanted to make a difference you can feel in your bones, 4.10 is the clear choice. That will really wake the truck up. I've done this a few times, don't waste your time and money with half-measures. 3.55 to 3.73 is a half-measure.

OhioLariat

I didn't realize he has 3.55 to begin with. (Should have checked the code.) Agreed. 3.55 to 3.73 isn't worth the effort or expense. Going to 4.10 (which is a stock ratio available in the 8.8) would be the way to go. And no, you won't be spinning the engine to the moon. You'll be approximating what the original tire size and gear ratio would have done. If you can;t do it yourself, find a friend who has the skills, buy some beer and pizza, and have them help you do the swap. On the other hand, if you're happy with the current performance, then case closed. Stay with what you have.

Jbrew

As basically said above, 4.10's or don't bother. Punches out at 4.023 for the offset, next higher ratio would be 4.10. You'll kick yourself if you don't, specially w/ a six cylinder. The less that little engine has to work , the better your mileage is going be.