GTPP to 3:55

[grue]

Frankly, the issue is not the final drive, its the gear ratios. I would have moved 1-5 shorter and closer to sixth gear.

time to expand my understanding

how does this all work? can you have the same individual gear ratios but a different final drive?

from a ford document i found this:

V6 standard | T4 standard | 5.0 standard
-----------------------------------------
1st - 4.236.......... 4.236......... 3.657
2nd - 2.538.......... 2.538........ 2.430
3rd - 1.665........... 1.665........ 1.686
4th - 1.2387......... 1.238........ 1.315
5th - 1.00............ 1.00.......... 1.00
6th - 0.704.......... 0.704......... 0.651

F.D. 3.15:1..... 3.31:1........... 3.31:1
F.D. 3.55:1..... 3.55:1........... 3.55:1
F.D. ...*............*................3.73:1

Then i found this on another website:
"With a ratio of say 3.23 for every 3.23 turns of the driveshaft the rear wheels do one full turn."

is 5th gear the "same" for all the cars it's just that they are different speeds for the same rpm because of the different final drive?

thanks!

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[Grintch]

Max speed in gears is a factor of rev limit, tire size, gear(box) ratio, and final drive ratio. Overall ratio (ignoring tire size) is gear ratio x final drive ratio.

For reference - 1st gear total ratio & speed in gear:
2015 GT PP (3.73) - 13.65 41mph
2016 GT350 (3.73) - 12.12 55mph (high redline)
2015 GT (3.31) - 12.11 46mph
1970 Boss 302 (optional 3.91 FD) - 10.87 44mph (significantly shorter tire makes up a lot of the gear ratio difference)

 

[Sasuketr]

I'm on 3.31's, I'm doing 2k rpm at 50mph in fifth. Can't really use 6th at 50mph because it drops that to 1250 rpm.

On my manual it says you can shift to sixth gear at 43 mph and above! I have the 3.73's! I think autocross is a blast with 3.73's cause the third gear can hold it upto 90 mph! Drag race, after 114 mph you have to shift to fifth gear so thats the only problem. If you are tuned and raise your rpm limiter than all holding you back is the grip on the first and second gear.

My car is not tuned but even after a light lunch on second gear, if i put my foot down the car looses traction, at the end of third gear it chirps as well! Loving the 3.73's!

 

[Cascadia_302]

Max speed in gears is a factor of rev limit, tire size, gear(box) ratio, and final drive ratio. Overall ratio (ignoring tire size) is gear ratio x final drive ratio.

For reference - 1st gear total ratio & speed in gear:
2015 GT PP (3.73) - 13.65 41mph
2016 GT350 (3.73) - 12.12 55mph (high redline)
2015 GT (3.31) - 12.11 46mph
1970 Boss 302 (optional 3.91 FD) - 10.87 44mph (significantly shorter tire makes up a lot of the gear ratio difference)

Tire size as you referred to can help (3.73 gears) if you don't mind running a 40 aspect ratio in lieu of 35's. But how you use the car may not make this a viable option.

 

[grue]

to answer my own question then is:

each individual gear has it's own gearing. that gearing could be the same on either a FD of 3.55 or 3.73, differences in RPMS @ MPH would be due to the FD gear as well as differences in top speed in any gear @ max RPM.

another way to think of it is that FD and individual gear ratios are completely separate things, but they work together to determine RPM @ 50mph or 30mph for 3rd gear or 2nd gear or 5th gear etc...

is this the right idea then?

time to expand my understanding

how does this all work? can you have the same individual gear ratios but a different final drive?

from a ford document i found this:

V6 standard | T4 standard | 5.0 standard
-----------------------------------------
1st - 4.236.......... 4.236......... 3.657
2nd - 2.538.......... 2.538........ 2.430
3rd - 1.665........... 1.665........ 1.686
4th - 1.2387......... 1.238........ 1.315
5th - 1.00............ 1.00.......... 1.00
6th - 0.704.......... 0.704......... 0.651

F.D. 3.15:1..... 3.31:1........... 3.31:1
F.D. 3.55:1..... 3.55:1........... 3.55:1
F.D. ...*............*................3.73:1

Then i found this on another website:
"With a ratio of say 3.23 for every 3.23 turns of the driveshaft the rear wheels do one full turn."

is 5th gear the "same" for all the cars it's just that they are different speeds for the same rpm because of the different final drive?

thanks!

 

[Grintch]

Tire size as you referred to can help (3.73 gears) if you don't mind running a 40 aspect ratio in lieu of 35's. But how you use the car may not make this a viable option.

If anyone made them. Which they don't in wider tires or in sticky tires.

 

[Socalmustang]

Can someone explain what the biggest advantage is in running the 3.73 gears? There's always a lot of talk that it's not good for FI and 3.31 is the best option for that route. They say 3.55 are a good middle ground between the 3 options.

Anyone that can clarify please do.

 

[Grintch]

Can someone explain what the biggest advantage is in running the 3.73 gears? There's always a lot of talk that it's not good for FI and 3.31 is the best option for that route. They say 3.55 are a good middle ground between the 3 options.

Anyone that can clarify please do.

In theory 12% more torque to the wheels.

But can you actually get that extra torque to the ground? Probably not, especially if you have forced induction.
And once you get out of 1st, you can easily be better off (have more torque) with taller gears. For example at 65mph, a 3.31 in 2nd will have more torque to the ground than a 3.73 in 3rd.

Downside is 12% slower in the gears (can require more shifts).
Harder to get power to the ground (if you're starting in 2nd, you need a taller FD).
And worse fuel economy.

 

[DivineStrike]

Right now I mind 373's but I know in the future I will be fine with them once I up the rev limiter. But that is at least a year or two away. My main gripe with them is not being able to hit 60 in 2nd, 4th being so short and top end of course. My other gripe is that going to a performance tire you are basically forced to drop the tire size .7 inches, exacerbating the effect of gearing :headbonk:

Guess I'll have to deal with hitting redline in autocrosses for a little while

 

[TrackpackGT]

First gear in the mt82 is stupid low. What it needs is a Magnum xl. 4th gear should be 1:1. I either want 3.55s/3.31's or save up for the xl conversion. Guys run great 1/4 mile times with those gears and I'd do much better on a road course with a 4th gear I can use.

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