Rear gear 327 or 331

[CraigS]

I am planning to swap out my 308 and was thinking 327 since that is the gear I see mentioned most often other than 355. But, i looked at Summit for Ford gears and they also offer a 331. I am surprised they would have two gears so close together. Is there something I missed and the 331 won't work in a Fox body 8.8 solid axle? Is there any reason I shouldn't go w/ the 331?

[Dan Babb]

Make sure you check out the speedo gears. You want to confirm that their is a gear that will work with the rear end you're using. Otherwise your speed reading will be wrong.

For example: I believe that using the right color gear that you'd need to be spot on with a 3.73 rear end doesn't really mesh with the drive gear in the stock trans, so you wind up eating up the gear. The solution is to either change out the drive gear in the trans (so remove & replace the tailshaft) or just live with the color gear for a 3.55 and live with your speedo being off by about 10% (that's what I did on my last car).

I wish my car had 3.55's now...but not going to spend the time or money to change it.

[charles roybal]

I vote for 327's. I'm very happy with the TKO 500 408w 530 hp. and 327's. Can use all the gears .....even 5th. at 55 mph.

[trevor]

craig, I think the 3.31 came out with the S194 style mustang. If I were you, Id go with that ratio for autoX. On most autoX courses I would hit the limiter in 2nd (3.27s) in a few spots with my power level. Im guessing with yours, you will need a tick lower ratio

[JKleiner]

It is simply a matter of gear count. 3.27:1 = an 11 tooth pinion gear with a 36 tooth ring gear while 3.31:1 = a 13 tooth pinion and 43 on the ring. The true ratio difference is just slightly more than 1%, something that you will never feel in the seat of your pants or see on your speedometer

Jeff

[frankeeski]

Ding, ding , ding! We have a winner. They are essentially the same ratio. My 2 cents would be to go with the stock Ford Racing brand. They just always seem easier to set up in the rear end housing.

[J Persons]

The 3.27 ratio should be the Ford Motorsport brand, they will be less troublesome to install than some of the other brands.
If you currently have a 3.08 rear end ratio and the transmission is a '83 through '89 T5, all you need to do is change the speedo driven gear to 21 tooth gear, it's very easy to do, just remove the gear on the end of the speedo cable and replace it with the 21 tooth gear. There is no need to go into the transmission in this case. The 21 tooth gear will be red in color.

[CraigS]

They are both Ford motorsport gears. i understand that the ratios are nearly interchangeable. I was just afraid i was missing something like the 331 only fits axles after 2005 or similiar. Thanks guys, I will go w/ the 331 for that extra 1% accelleration!!

[Wade Chamberlain]

Craig-
My 3.31's are take-outs from a new Shelby GT. No problem in the old 8.8, and if you keep your eyes open, you can pick up a used set for $50.

[edit] - forgot to mention...w/ a 6800 rpm rev limit, it'll run 76 mph in 2nd, and a 7-tooth/19-tooth speedo gear combo is less than 1% error w/ 315's.

[Bill_VA]

This looks like a good deal on a set of 3.27 gears. I'm not ready to pull the trigger, so have at it:

Ford Mustang 3 27 Gear Set Ring and Pinion 8 8 Axle Gears Good Used Take Out 3 | eBay