Ford's official answer to what gears you should put in your car

[Aftrbrnr]

Taken from Ford Racing Parts FAQ:

http://www.fordracingparts.com/faq/faq.asp

Q.: I have heard that an axle gearset change is a very effective way to increase performance in my Mustang. What gear ratio do you advise that I use?

A.: 1986-95 Mustangs with a 5.0 and a 5-speed work well with 3.55 gears.
1986-95 Mustangs with a 5.0 and an automatic work well with 3.73 gears.
1996-2003 Mustangs with a 4.6 SOHC and a 5-speed work well with 3.73 gears.
1996-2003 Mustangs with a 4.6 SOHC and automatic work well with 4.10 gears.
1996-2001 Mustang Cobras with the 4.6 DOHC/5-speed work well with 3.73s.

Note: The above suggestions are general recommendations. Gear-ratio selections may change depending on modifications to your engine. For specific applications, call the FRPP Tech "Hot Line" (586-468-1356) for professional advice.

 

[custom89stang]

thanks for that, they are completely right. i heard its hard to drive in the rain with a stick an 3.73's in a 87-93 that i have. my mechanic told me to get 3.55's because it takes away from top end speed to much to go higher than that...so overall i must say i agree w/ almost all their recommenations...thanks for the post though


oh yeah my mechanic owns a mystichrome cobra 2004 and a superchargered 347 stroker....in a 5.0 so he knows what hes talking about

 

[5spd GT]

I actually completely agree with the suggestions made there. It makes sense and has reasons behind it.

custom89stang - There is very little difference in the topend speed (actually might be better for you if you don't have many mods for topend pull) between 3:55's and 3:73's. You made a good choice either way

 

[maverick0716]

The top end speed issue is kind of BS. I have 3.73's and I can go 180 kph in 4th gear at only 5300 rpm. Even with 4.10's you could easily go over 130 mph in 5th gear.

 

[Michael Yount]

"There is very little difference in the topend speed (actually might be better for you if you don't have many mods for topend pull) between 3:55's and 3:73's. You made a good choice either way"

I agree with my buddy 5spd completely on this one. With mild mods, top end is probably enhanced with 3.73's. And there's not enough difference between 3.55's and 3.73's to worry with. Toss a coin. Get the ones that you can get the best deal on.

By the way, the gear ratio difference between 2.73's and 3.73's is almost identical to the difference between 4th and 5th gear in the original T5's. So if anyone wants to highway 'test drive' 3.73's, just leave it in 4th gear on the Interstate. You can check cruising rpm, top speed and fuel mileage impact before you ever make the switch.

 

[bobbyd]

hehe nice mine is a AOD and those are exactly the gears I want 3.73 is there a loss on top end on those for a AOD? or any kind of loss at all?

 

[Michael Yount]

The ratios of 3rd and 4th in an AOD are about the same as the ratios of 4th and 5th in the T5 - so the results are the same with regard to top end. Of course, with a torque converter, there's some slippage, so knowing how revs will be impacted is slightly different.

 

[JCVERT]

In my car when I had a stock motor last year I tried that I went in 4th gear the whole time on the freeway and I got better gas mileage by staying in 4th rather than 5th, mind you I had 2.73's and 5th gear was a really meant for fairly high speed only.

 

[willys1]

"There is very little difference in the topend speed (actually might be better for you if you don't have many mods for topend pull) between 3:55's and 3:73's. You made a good choice either way"

I agree with my buddy 5spd completely on this one. With mild mods, top end is probably enhanced with 3.73's. And there's not enough difference between 3.55's and 3.73's to worry with. Toss a coin. Get the ones that you can get the best deal on.

By the way, the gear ratio difference between 2.73's and 3.73's is almost identical to the difference between 4th and 5th gear in the original T5's. So if anyone wants to highway 'test drive' 3.73's, just leave it in 4th gear on the Interstate. You can check cruising rpm, top speed and fuel mileage impact before you ever make the switch.

"I agree with my buddy 5spd"?? I just lost my appetite ,,Those gears "mite" have the same top speed,but the pull getting there will be different!!

 

[5spd GT]

"I agree with my buddy 5spd"?? I just lost my appetite ,,Those gears "mite" have the same top speed,but the pull getting there will be different!!

What is your point?

 

[5spd GT]

In my car when I had a stock motor last year I tried that I went in 4th gear the whole time on the freeway and I got better gas mileage by staying in 4th rather than 5th, mind you I had 2.73's and 5th gear was a really meant for fairly high speed only.

Yeah to fight against the "lack of power" down low (low crusing rpm) and the aerodynamics you might have to give it more gas to sustain a speed. That would be the reasoning behind the mpg gain you received. I'm sure at a higher speed (as you alluded to) the 5th gear would be better

 

[Michael Yount]

yup....Ford didn't put the long 5th gear in just to keep revs low; they put it in because it made for better highway mileage.

 

[willys1]

What is your point?

My point is if you have 2 indentical 5.0's with the same trannies,1 having 355's and the other having 373's(I really wanted to use 410's for this comparison) Let just say for example their top speed is 140..(Its just an example) If the 2 cars were at a steady speed of 100mph and then floored it the car with 355's would reach 140 before the other one,or it would "pull" harder!!,,hence the term "pull"

 

[89MustangGX]

My point is if you have 2 indentical 5.0's with the same trannies,1 having 355's and the other having 373's(I really wanted to use 410's for this comparison) Let just say for example their top speed is 140..(Its just an example) If the 2 cars were at a steady speed of 100mph and then floored it the car with 355's would reach 140 before the other one,or it would "pull" harder!!,,hence the term "pull"

If you want to have a comparison and assume that all things are equal -- the higher numerical gears should reach a given speed quicker...at least if my thinking is correct.

-----

I like more gear in my car -- I don't want to disagree with the FMS recommendations, but I think they do not fit everyone.

 

[5spd GT]

My point is if you have 2 indentical 5.0's with the same trannies,1 having 355's and the other having 373's(I really wanted to use 410's for this comparison) Let just say for example their top speed is 140..(Its just an example) If the 2 cars were at a steady speed of 100mph and then floored it the car with 355's would reach 140 before the other one,or it would "pull" harder!!,,hence the term "pull"

Well I'm going to take the comparison you said literally (identical 5.0L's as in everything the exact same down to the ounce of gasoline in the tank)...the 373 car will pull ever so slightly harder to that given point of 140mph. Barely noticeable. The rpm at that given punch (about 3400rpm or so) is pretty ideal in that powerband in 5th gear.

 

[willys1]

If you want to have a comparison and assume that all things are equal -- the higher numerical gears should reach a given speed quicker...at least if my thinking is correct.

-----

I like more gear in my car -- I don't want to disagree with the FMS recommendations, but I think they do not fit everyone.

Yeah your rite in thinking that,but stock 5.0's work better in low rpm's.So at a 100mph the car with 355's is gonna be at a lower rpm and will have more power!!(not much but a little) Yeah Im sure the FMS tech line is pretty conservitive when it comes to performance parts and modding.

 

[5spd GT]

Yeah your rite in thinking that,but stock 5.0's work better in low rpm's.So at a 100mph the car with 355's is gonna be at a lower rpm and will have more power!!(not much but a little) Yeah Im sure the FMS tech line is pretty conservitive when it comes to performance parts and modding.

At the given rpm of those gears...the 373's will "overpower" it. A 5.0L is faster from 3k-4k than 1k-2k.

A 5.0L isn't "faster" at a lower rpm...

 

[willys1]

Well I'm going to take the comparison you said literally (identical 5.0L's as in everything the exact same down to the ounce of gasoline in the tank)...the 373 car will pull ever so slightly harder to that given point of 140mph. Barely noticeable. The rpm at that given punch (about 3400rpm or so) is pretty ideal in that powerband in 5th gear.

Your wrong! 0-100 goes to the 373 car. 100-140 goes to the 355 car.And thats all DAVE,,,I will not argue about a race with 2 cars in OD

 

[willys1]

At the given rpm of those gears...the 373's will "overpower" it. A 5.0L is faster from 3k-4k than 1k-2k.

A 5.0L isn't "faster" at a lower rpm...

It is alot faster in the low rpm's then it is in the high rpm's!!

 

[5spd GT]

Your wrong! 0-100 goes to the 373 car. 100-140 goes to the 355 car.And thats all DAVE,,,I will not argue about a race with 2 cars in OD

willys1, I'm not sure you should be arguing this point. It simply isn't true. The given rpm range at 100mph with those gears is going to give the 373's the slight advantage (noticable? I let you decide that one). The 373 geared car will out accelerate it in every gear ever so slightly due to it's higher ramped gear/torque mulitiplication.