What kind of mileage would I get...

[MarquisMalarky]

...if I put in different rear end gears? I like how the car idles on the highway, but as soon as I tap the gas it bumps down to third and is kind of annoying. I'd like a little more get-up-and-boogie, too. I could swap in some other gears, but I don't know what my options are or where I'd get them. My friend has a wrecked 94 Mustang, I could probably take the rear end outta that.

I'd also like posi traction too.

What kind of mileage would I lose depending on what gears I have?

[Tiggie]

What do you have now? A 3.55 upgrade is usually the middle of the road, 3.27 if ride highway a lot, 3.73 or 4.10 if you run mostly around town. If the 'Stang still has the stock gears, don't even bother looking, they'll be 2.73's for a manual and 3.08's for an auto unless it's a Cobra. You'd only be able to use the ring and pinion anyway.

[MarquisMalarky]

I do a lot of highway driving. I was told that I have 3.77 gears or something like that?

Where would I find some 3.27's? I'd probably feel a difference in acceleration from that.

[gadget73]

Could buy them new or find them used. Most likely if its a stock rear, you've got a 2.73 or 3.08 gear. Some tow package cars got a 3.55. Signature series Towncars often got a 3.27, Mark VII LSC got them too.

[Tiggie]

I've seen a totally unproportional amount of 3.27's in '87 Boxes for some reason. It seems every other one at the junkyards has a 5 or an E for 3.27's.

What does your car have now? Check the axle code on the door, or crawl underneath and look sometime.

You mileage may actually go up if it's hunting between 3rd and 4th now if you choose the 3.27.

To give you an idea of the differences between the gears, these are your rpms with a P215/70-R15 tire theoretically in OD with a stock AOD at 60mph:

2.73 - 1374
3.08 - 1550
3.27 - 1646
3.55 - 1787
3.73 - 1877
4.10 - 2063

[MarquisMalarky]

What's the axle code look like?

[Nathan in MI]

It's on your door sticker under the "AX" heading.

[MarquisMalarky]

the axle code is an 8. What does that mean?

[mrltd]

From the drivetrain FAQ....

2.73 open: 8
2.73 locker: M
3.08 open: Y
3.08 locker: Z
3.27 open: 5
3.27 locker: E
3.55 open: 2
3.55 locker: K__________________

[88grandmarq]

If you do a lot of hwy driving, 3.27 would be the best choice. you would drop maybe 1 mpg with that sort of gear change.

you can pick up used 3.27 for gears on corral or stangnet all day long for $40-$50

[MarquisMalarky]

Sounds good, Hope to find a 3.27 locker somewhere.

Thanks a bunch guys, I appreciate it.