1trickpony

Its probably not worth the time and money to swap out a 3.31 for a 3.55. You probaly couldn't tell the difference.

hamidlmt

Way down the road I may consider gears and a t-lok, but I'm diggin' the way the car drives on the highway now, so maybe just the t-lok. Lotta great info in this thread! Thanks to all!

JesseV6

Thanks Brian, I have a little time to think while I save up but I am leaning tward 3:73 now

Zodiac

Brian,

Let me get it straight then, you say 3.73 or 4.10 for the v6 manual? And can we get that same breakdown you did for the auto?

Gearhead

Hi Richard,
Great idea to compare the 3.73:1 to the 4.10:1.
For the Manual Transmission, 1st gear is 3.75:1, 2nd gear is 2.19:1, 3rd gear is 1.41:1, 4th gear is 1:1, and 5th gear is 0.72:1
1st Gear at 5,300 RPM with the 3.73:1
Speed = (5,300 rev/min)(60 min/hr)(1/3.75 3rd gear)(1/3.73 axle ratio)(0.0013387 mile/rev) = 30 MPH
1st Gear at 5,300 RPM with the 4.10:1
Speed = (5,300 rev/min)(60 min/hr)(1/3.75 3rd gear)(1/4.10 axle ratio)(0.0013387 mile/rev) = 28 MPH
3rd Gear at 5,300 RPM with the 3.73:1
Speed = (5,300 rev/min)(60 min/hr)(1/1.41 3rd gear)(1/3.73 axle ratio)(0.0013387 mile/rev) = 81 MPH
3rd Gear at 5,300 RPM with the 4.10:1
Speed = (5,300 rev/min)(60 min/hr)(1/1.41 3rd gear)(1/4.10 axle ratio)(0.0013387 mile/rev) = 74 MPH
70 MPH Cruising with the 3.73 in 5th gear
Engine Speed = (70 miles/hr)(1/0.0013387 rev/mile)(3.73 axle ratio)(0.72 5th gear)(1/60 hr/min) = 2,340 RPM
70 MPH Cruising with the 4.10 in 5th gear
Engine Speed = (70 miles/hr)(1/0.0013387 rev/mile)(4.10 axle ratio)(0.72 5th gear)(1/60 hr/min) = 2,573 RPM
To summarize:
Axle Ratio .. 1st@5,300 RPM .. 3rd@5,300 RPM .. 5th@70 MPH (% of 3,500 RPM)
.. 3.73:1 ........ 30 MPH ............... 81 MPH ........ 2,340 RPM ....... (= 65%)
.. 4.10:1 ........ 28 MPH ............... 74 MPH ........ 2,573 RPM ....... (= 74%)
So, it looks like:
1st gear isn't too big an impact for Chirp-'em capability with either ratio, and
3rd gear seems better suited to the 3.73:1 for passing which concludes at 81 MPH, and
5th gear cruising for mileage would be better with the 3.73:1. With a lightly loaded engine, 2/3s of peak rated torque (3,500 RPM) would be better for mileage than one turning more like 3/4s of peak rated torque. I would guess that the mileage for a highway cruise would be:
3.31:1 = 28 MPG (EPA RATING)
3.73:1 = 27 MPG (guessing)
4.10:1 = 26 MPG (guessing)
I will stick with the 3.73:1 for my manual transmission.
I hope this helps; thanks, Brian.

ManEHawke

Very helpful, and informative!

1trickpony

Gearhead,

What's wrong with taking it to redline (5900)? I noticed you used 5300 rpm for all of the calculations. The engine will put down 90+ percent of its peak HP at redline. I would not short shift with this engine.

Greg

Gearhead

Hi Greg,
That is a great point. Absolutely nothing is wrong with taking it to redline. I frankly didn't know what redline was for the car. My car will arrive in late September or October. I have been getting my information from here:
http://www.fordvehicles.com/cars/mus...eatures/specs/
http://www.fordvehicles.com/assets/p...tang_specs.pdf
and the information does not include redline. Textbook redline for engines made with 50+ year old material used to be calculated by an average piston speed of 2,500 feet/min. The 4 Liter V6 has a stroke of 3.32", which means piston speed at 5,900 RPM = (5,900 rev/min)(3.32 inch/stroke)(2 strokes/rev)(1/12 feet/inch)
= 3,265 feet/min.
Sounds about normal for modern engine materials, however, I notice that the materials chosen for the V8 are lighter and tougher than the materials for the V6. For example:
The V6 Pistons weigh 15.87 ounces, and are made of Cast Aluminum
The V8 Pistons weigh 12.63 ounces, and are made of Hypereutectic Aluminum Alloy.
I am green with envy already
Yes, if we could get a power curve for the engine, we could calculate what would keep the kettle on the boil at a maximum, on both ends of the shift. Then again, we should also keep in mind the fuel economy at cruise, since many of us bought this car to get the most smiles per dollar, whether it be for Insurance reasons, or that it was quick enough anyway, etc. The 4.10:1 I am sure will do more poorly in terms of fuel economy at a highway cruise than would the 3.73:1, wouldn't you agree? I think my main objective in getting down to the 3.73:1 is to get a better ratio for around-town driving, have a little pep in 5th gear, have a great ratio for 3rd gear passing, and maybe be a little easier on the clutch.
Thanks; Brian.

1trickpony

I'm with you. The maximum engine speed is 6100 rpm, the indicated redline is 5850 and that should be upshift limit for an automatic. I guess you could take a manual to 6100 and the auto to 5850 unless you override the ECU. The PDF above has the rpm limit and shift point for in the text. Superchips has a dyno for the 4.0L. A couple of guys have posted their dynos on another site. I know numbers will vary dyno to dyno, but the torque curves should be consistent. Interesting point, it looks like the Mustang was making more power at high rpm than a 4.0L Ranger. If ther dynos are good, the Ranger had less peak HP and dropped off faster. So much for manufacture's numbers. I agree with you about the 4.10s If I drag raced I would get 4.10s. For my daily driver, 3.73 with a T-loc should do it. The performance wouldn't change much. Chevy High Performance did a comparison of gear ratios. The difference between a 3.5 and 4.11 rearend was .2 of a sec in the quarter with drag radials. On street tires, probably less because it won't hook up. Max piston speed is sometimes displayed at media.ford.com in meters per second. I would be scared to redline a 5.4L. Thank you for the numbers.

Thomas S

You and JennStang(http://forums.stangnet.com/member.ph...oster&t=562226) need to get married and have super-genius babies.

Gearhead

With JennStang from the StangNet Forums, and me from the BradBarnett Forums, you know it would never work out.
We are just from different sides of the track.

justgreat

5300 rpm is a good reference point for hp numbers and calculations versus redline, simply because 5300 is the rpm where the 4.0 makes it's peak power...anything higher and the power starts to drop off. redline is the maximum engine speed recommended by the manufacturer. if you're trying to squeeze the last bit of power out of the motor, shifting at 5300 will be your best shift point.

by the way, i LOVE this thread. jackg 90seville 97k

Thomas S

Actually, you want to shift at a higher RPM than your peak so that you stay in the powerband in the next gear. 5800 would be about ideal.

1trickpony

The best way someone put it was some guy at Car and Driver. You want to shift when shifting will get you more HP, redline accepted. I drove a 94 GT for 5 years. Loved the car but it died about 5000rpm. peak HP was 4200 rpm. I would still redline 1st (5800 rpm) because that put the motor at the bottom of the powerband in 2nd. I would shift at 5000 rpm after that. That put me at 3300 rpm in 3rd. The old 5.0 was making more power at 3300 rpm versus 5800 rpm so it paid to shift early. Trivia, I test drove the 4.0L and think its about as fast as my 94 GT. That's progess.

justgreat

IF you're concerned about TIME to DISTANCE and you're shifting beyond the maximum power output of the motor, then all that time spent beyond the max power rpm is time lost. in fact, because of the time between DECIDING to shift and ACTUALLY shifting, you have gone over the max power rpm setting. you should be shifting about 2-300 rpms BEFORE max power rpm.

now, if the gearing of the transmission creates a "hole" when shifting to a higher gear, that's a problem that you have to live with. you can shift beyond the max power rpm and hit the sweet spot for the next gear, but time is time: it's taking longer to either shift "late" because of the hole or shifting at the peak hp rpm and waiting for the power to build.

jackg 90sevile 97k

1trickpony

I have to disagree. Where does this information come from? Average HP should be the money maker. Have you done this with a car? Sorry if that's too personal, but some practical application will quickly make the point. Ask anyone if they're are short shifting at 5000 rpm to get the best ETs. Most guys want to raise the rpm limit, especially on the GT. I not Evan Smith at MM & FF, but I've used a stop watch before and experimented. With the 4.0L, 300 rpm below is a short shift at 5000 rpm. You'll shift three times (fourth gear) in the quarter. Redlining third will save me a shift and time in the quarter. HP moves the car. Some might say torque, but that's another discussion. Redlining in this case will increase average HP or ability to do work, decreasing the amount of time to cover a given distance. Please bare with me, I studied Management, so I not that good with formulas.

Gearhead

Hi All,
Honestly, most of us purchased a V6 without consideration to the best quarter mile runs. Above all else, optimizing your gear ratio for 3rd gear passing is pretty much what it is all about. On a two-lane highway, you will want to drop from either 5th or 4th down to 3rd, and hammer the throttle to get around some guy before the on-coming log truck runs you out of room. :shock:
Since most passing on a two-lane highway would be concluded by the time you reach 80 MPH, it certainly makes no sense to gear maximum horsepower above that speed. A little lower would be OK, but not having to shift in the on-coming lane is a good thing.
Brian.

1trickpony

I agree with you, passing power/ability is really where its at for most folks.

justgreat

okay...a couple of different items on the same basic subject: first, i do not race and so i defer to you regarding your point about the number of shifts in the q/m. you have done your homework in that regard. BUT, in one way you did prove part of my point: time IS time...but in the case of the extra shift the way to get "around" it is to shift beyond the max power rpm, this way you save tons of time by saving a shift in the quarter.

the point about the 5th to 3rd shift is definitely a street application and it will do wonders for acceleration. keep in mind that the transmission in the mustang is really a four speed with overdrive. i point this out simply because if you look at the tach at cruising speeds (60 mph) you will find that in top gear you are turning well below the optimal rpm range which is usally half of the max power rpm (2600/2700 at 60 mph in top gear). in the mustang you're not even close to that number...that's why you need to downshift to 3rd...unless you're doing 80 or so, in top gear, you're no where near the sweet spot for the engine...that's why it's really a four speed with the fuel economy 5th gear. jackg 90seville 97k

ex-Galaxie500

So has anybody actually switched out their gears yet? Did you run into the problems some GT owners have? Information and numbers are nice but some experience would be great to hear about...