Peetza

If you don't mind a little drive to Harrisburg, Pa. check these guys. Great price, Super Service. You won't be sorry. They did my gears perfectly. They know to stay away from Motive. These are real Mustang guys.
http://www.cjponyparts.com/ford-raci...xle/p/M420988/

http://www.cjponyparts.com/default.asp

Nuke

Our top end is ultimately limited by the coefficient of drag. These engines don't make enough HP where the gear comes into play. Regardless if you have 4.10's or 3.31's, you won't be able to redline in top gear, period.

Fuel mileage will not suffer too dramatically. If you do 50/50 highway/city don't expect to see any more than an average drop of about 2 MPG.

alkemist

This is partially incorrect. Gears do not increase HP nor does it increase TQ but the higher the gear ratio, the faster the torque delivery.

There is JPC racing in Maryland and there was a shop down in VA. Not sure if you are part of http://www.mdpatriotstangs.com, you can hook up with some advice on local shops there.

HareBrained

The rear end ratio is how many times the driveshaft turns (4.1) to one revolution of the tires. Going to numerically higher gears means the engine will have to spin faster to get the same ground speed (assuming no slippage in the drivetrain.)

Grabber, please edit your original post to eliminate the mis-information.

grabber blue gt

Wait I thought it was 1 turn of the drive shaft to 4 turns of the wheels with 4.10s? Its 4 turns of the drive shaft to one turn of the wheel?

HareBrained

"Faster" is not quite right either. The axle gears are a multiplier, like using a longer lever to break loose a bolt. You're trading distance (in this case more engine/trans revs) for increased applied force. So, gears don't change torque output at the engine but it does change the amount of torque applied to the wheels. This evident in this 5.0M&SF article. Swapping the stock 3.31:1 gears for a set of 4.10s netted a change in the rwh/tq of -20/-20. The engine didn't change but the manner in which it was applied did. In the end, it does result in faster acceleration but lower top speed (this isn't evident in a quarter mile because the 'stang is still accelerating at the end of the race track.)

HareBrained

Yes. Think about the pinion. It's circumference is smaller than the distance around the ring. Numerically higher ratios have a smaller pinion gear diameter (room for increasing the ring diameter is very limited).

Or think about the results: a higher ratio requires more engine rpms to yield the same road speed. In order for that to happen, the driveshaft also has to turn more and if we were to go by your definition, the opposite would be true.

grabber blue gt

o0o wow, thanks for correcting me !

HareBrained

{how does one edit a previous post?}

Just to clarify (you may see the "increase applied torque" and the decrease in measured output): In using a breaker bar, the actually amount of torque applied to the breaker bar is LESS but that applied to the bolt is MORE than without the breaker bar. So in measuring the forces with the dyno, the amount put out by the system is less due to the multiplication but the resulting torque applied at the tire patch (shearing force) will be greater, turning them to smoke with greater ease.

alkemist

That is essentially what I said.. I never said anything of the engine producing anything different nor did I say the torque output changes.