2015+ GT350 Mustang official power specs: 526 HP / 429 LB-FT!

[D K]

Anything shorter than 1:1 should never be used (an I guarantee it was engineered to NOT be used) as an acclerating gear. Those are overdrive gears and should (and are designed to be) used as cruising gears


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Vipers and Camaros still accelerate in 5th....

It comes down to what the final drive is.

Multiply the gear ratio by final drive to get an overall ratio.
12.xx first
2.4 6th

Etc etc


There are a couple of good online calculators that are free and easy to use.
http://www.americantorque.com/graph-rpm-vs-speed/

D

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[thePill]

Absolutely not.

And that was the point I was trying to make.


If you want to go around the track fastest, you should gear much shorter.

IE topping out at 160 ish depending on track

Not sure about 160mph...

Sebring was said to be around 150mph as well as VIR's front stretch.

It was also rumored the GT350R prototype reached 170mph at Nurburgring in the 3km straight.

I think 160mph at a U.S. track will be very, very difficult.

 

[GrabberBlue5.0]

I know what you are saying, but overdrive gears are taller than their underdrive gears, not shorter. Just a terminology tip . It's sometimes confusing to a lot of people that bigger #s = short, smaller #s = tall.

Thanks for catching that, I knew that but I always confuse it anyways lol

Vipers and Camaros still accelerate in 5th....



It comes down to what the final drive is.



Multiply the gear ratio by final drive to get an overall ratio.

12.xx first

2.4 6th



Etc etc





There are a couple of good online calculators that are free and easy to use.

http://www.americantorque.com/graph-rpm-vs-speed/



D

I realize they "can" accelerate with those gears but that does not mean they're designed to accelerate, at least not at wot for long periods of time. With overdrive gears the frictional losses are greater and cause a lot more heat for very little in return.

Think of it this way, imagine you're on a 10 speed bicycle, cruising at a comfortable speed in 10th gear, then you want to speed up and speed up quickly, and maintain a higher rate of speed for some duration of time. Will you stay in 10th gear to do all of this or will you switch to a lower gear that will make it easier to speed up and maintain a higher speed?


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[Conedodger]

Not sure about 160mph...

Sebring was said to be around 150mph as well as VIR's front stretch.

It was also rumored the GT350R prototype reached 170mph at Nurburgring in the 3km straight.

I think 160mph at a U.S. track will be very, very difficult.

Daytona ?

 

[Grimace427]

This gearbox was run successfully in Grand Am and much taller than a 5.xx rear.
3.9's, 4.1's etc.

Mind you, this was on a Coyote motor, so adjusted, youd want maybe 15% shorter on the Voodoo.

Im trying to point out the fact that the 'spread' on a road race car neds to b much shorter than a street going car.
In the 56R case, its only 1.53 divided between 6 gears!

And that seemed to be the magic formula.

In the 3160 case, its 2.6, and thats with a very tall and un useable 6th gear.

Food for thought?

I'm well aware of the T56 used in the race cars, and as you mentioned they were not connected to the 8,250rpm Voodoo engine. The close ratio transmissions would require crazy short rear gears to make any gear below 100mph useful. With the 3,160 and 3.73 the top speed will be in direct drive as it should be with the 6th gear being for highway cruising. Let's not forget this is still a street car.

Hypothetical GT350 with the tight-ratio Tremec road race trans:
305/35/19 tires, 3.73 gears:

1. 2.29............78mph
2. 1.61............111mph
3. 1.21............148mph
4. 1.00............179mph
5. 0.82............219mph
6. 0.68............264mph......1,850rpm @ 60mph(not even as good a highway gear as the 3,160)

With 4.10 gears:

1. 71
2. 101
3. 135
4. 163
5. 199
6. 240...........2,050rpm @ 60mph

With 4.30 gears:

1. 68
2. 97
3. 128
4. 155
5. 190
6. 229..........2,150rpm @ 60mph

Now compare to the Tremec 3160 with 3.73 gears:

1. 55
2. 81
3. 111
4. 145
5. 179
6. 285...........1,750rpm @ 60mph

 

[D K]

Not sure about 160mph...

Sebring was said to be around 150mph as well as VIR's front stretch.

It was also rumored the GT350R prototype reached 170mph at Nurburgring in the 3km straight.

I think 160mph at a U.S. track will be very, very difficult.

I agree.

So 150 then?


That means overall gearing should be even shorter...

 

[D K]

I'm well aware of the T56 used in the race cars, and as you mentioned they were not connected to the 8,250rpm Voodoo engine. The close ratio transmissions would require crazy short rear gears to make any gear below 100mph useful. With the 3,160 and 3.73 the top speed will be in direct drive as it should be with the 6th gear being for highway cruising. Let's not forget this is still a street car.

Hypothetical GT350 with the tight-ratio Tremec road race trans:
305/35/19 tires, 3.73 gears:

1. 2.29............78mph
2. 1.61............111mph
3. 1.21............148mph
4. 1.00............179mph
5. 0.82............219mph
6. 0.68............264mph......1,850rpm @ 60mph(not even as good a highway gear as the 3,160)

With 4.10 gears:

1. 71
2. 101
3. 135
4. 163
5. 199
6. 240...........2,050rpm @ 60mph

With 4.30 gears:

1. 68
2. 97
3. 128
4. 155
5. 190
6. 229..........2,150rpm @ 60mph

Now compare to the Tremec 3160 with 3.73 gears:

1. 55
2. 81
3. 111
4. 145
5. 179
6. 285...........1,750rpm @ 60mph

Yes.

Its a moot point really since its a street car.

Although the 56r had a .76 6th in one version at least.

So for a road race car what would your ideal ratios be?



PS I did say before that the 3160 looks pretty good, save for the awful 6th

 

[grayforge]

Pacific Raceways here in Seattle has a front straight that I could reach 150mph on in an STi. 160mph in a GT350 might not be too tough.

 

[D K]

Pacific Raceways here in Seattle has a front straight that I could reach 150mph on in an STi. 160mph in a GT350 might not be too tough.

How is that track?

I was gonna go check it out.
We just left seattle and cruising the san juans right now.

 

[Grimace427]

Yes.

Its a moot point really since its a street car.

Although the 56r had a .76 6th in one version at least.

So for a road race car what would your ideal ratios be?



PS I did say before that the 3160 looks pretty good, save for the awful 6th

I pulled those ratios from the SCCA tech sheet, there's probably several more but I just don't like how 4th is 1:1 with two more gears on top of that.

I would run the gear ratios as is and decide if I like them after I actually put the car on a track. VIR and Summit Point would be my tracks.

 

[krt22]

Would be interesting to see what the factory race cars will come with, but from what is published the ratios seem pretty good, shortening them up too much might get you into a place where you are shifting where you don't really need to be since the powerband is so broad.

 

[grayforge]

How is that track?

I was gonna go check it out.
We just left seattle and cruising the san juans right now.

It's awesome, if scary in parts (turn 5b). They call it the Million Dollar Corner.

It's an interesting/technical track. Very exciting! My favorite among the local tracks (Portland and Spokane) that I've been to.

 

[D K]

I pulled those ratios from the SCCA tech sheet, there's probably several more but I just don't like how 4th is 1:1 with two more gears on top of that.

I would run the gear ratios as is and decide if I like them after I actually put the car on a track. VIR and Summit Point would be my tracks.

Ive raced SP but not VIR yet.
Was trying to get my car ready for Ultimat Track Car Challenge, but as usual, my fabricator is on his third menstrual cycle for the month.

On the west coast, we have Willow Springs which is pretty long and also Cal Speedway roval.

Im with you in a sense that I also dont like double overdrives.
Each gear should have half the drop as the change before is how Ive been taught and that seems to work.

So, a 1:24 to 1:00 would dictate a .88 6th following that math.

 

[D K]

It's awesome, if scary in parts (turn 5b). They call it the Million Dollar Corner.

It's an interesting/technical track. Very exciting! My favorite among the local tracks (Portland and Spokane) that I've been to.

Its good to know!

Im trying like hell to relocate here to the PNW (I work on big yachts), so I can get out of the dreaded Bahamas/Caribbean milk run.

 

[krt22]

Most excellent first world problems:cheers:

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