limited slip or air locker?

[OFG]

Im planning on swapping out the 3.55 gears in my 99 sport for 3.73 or 4.10 gears. Dont know wich to get. Tires will be 31-10.5-15. Already, I dont like the stock 3.55 gears, as the acceleration is somewhat lack luster. If I goto the 31" tires and 3.73 gearing, will the overal drive ratio be about the same as 235-75-15s and the stock 3.55 gears? Do the 4.10 gears really make a big difference in fuel mileage, especially with 31" tires? I would like to maintain 18 mpg, and see better acceleration even with slightly taller tires. Oh yes, and also, wich is preferred, a factory ford limited slip diff, or an aftermarket locker for the standard diff? Planning on getting my gears off ebay or at the junkyard if they have em and can match or beat an ebay price. Goin to the junkyards this friday and doin some serious shopping!

 

[RiverRat]

You are gonna take this thing off the highway right?

Get a locker. LS won't do it if you have a tendency to have a tire up in the air.

4.10s will give the best power/driveability with 31s.

 

[Bronco638]

OFG,
What RiverRat said.

I was considering the same thing, switching from 3.55s to 3.73s. After doing some research and trading PMs with a few Forum members, I'm going with 4.10s (& 31" tires). I don't drive my Ex on a daily basis so gas milage isn't as much of an issue with me. As for lockers versus limited slip, I'm going with lockers. Unless you do the work yourself, it's pretty expensive to rip apart a diff in the Explorers. Since you're going to change carriers, you'll need to be able to set the backlash (which requires special tools). You should also consider a bearing kit while you're at it. If it's all ripped apart, you might as well do the job right the first time.

Dave.

 

[OFG]

axles and pumpkins

Found a set of code 42 4.10 front and rear ends for 500.00 plus exchange for my parts. I think this is for a complete rear axle assembly and a complete front diff assembly. Is this a good price?

 

[Robert]

I wouldn't be too concerned about any mileage penalty going with the 4.10s. My '97 came stock with 4.10s and 30" tires. I averaged about 18-19 on the highway and peaked at 20 once. Once I went up to 32" tires, my mileage went up by another 1 MPG. Your 31s are in between my stock 30s and my then 32s. If you were to go with 3.73s and drive more city miles than highway miles, then you will likely loose mileage since they will take a little more effort (not much though) to get the tires turning. If you spend more time on the highway, 3.73s might gain you a bit more mileage (probably less than 1 MPG though). Just for the added accleration that the 4.10s will offer over the 3.73s would be enough for me to justify any possible mileage loss.

 

[Bronco638]

OFG,
I'm not sure I understand the 'code 42' part of your post. Is that a Ford code? "a complete rear axle assembly and complete front diff assembly" for $500? That sounds like a great deal. I plan to spend $400 for front and rear rings, pinions and bearings alone.
D.

 

[OFG]

Thanks guys. This rig will see off highway action. Mostly camping, and messing around in the desert, climbing hills. Dosent look like it will be ready for the Easter safari in Moab. Looks like the rear axle found is open diff, so a locker is the next consideration. . If Im not mistaken, 42 refers to an axle code on the door sticker. 42 being 4.10 ratio, open diff. Need to do a bit more research and see wich locker is best suited for normal street driving.

 

[Bronco638]

OFG,
With respect to lockers, I've decided to go with PowerTrax's No-Spin unit front and rear. If you want to go Detroit Locker, there's someone here in Chicago that selling one for $500 shipped. New, in the box for the Ford 8.8.

If you can locate the tag on the diff cover, that will indicate the ratio and differential type (S=Open, L=Limited Slip), too.

D.

 

[cdsl227]

Here you go-

Gear Ratio Guide

 

[karl_burns]

Check www.car-part.com

I found code 42s (4.10 Open) in my state for as low as $200 with only 34K miles on them. I admit some places wanted twice that, but car-part searches and then sorts by price for you!
Worth a try.
Karl