Help me choose the correct gear!

Five Oh Brian

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Another thing to note about these automatics, is when paired with the right converter, traction, they all seam to run pretty damn good, and a gear change can probably make the car feel alot different, but if tuned properly, you probably won't see much difference at the track imo. There's people that think that so and so's geared too low, and so, and so went faster with factory gears. I really think Five Oh Brian should swap in some factory 3.15's or 3.31s, make some hits at his local track, run the same number and put this to rest, hahaha!

My original 3.15's are in a box in my garage. I believe they are gonna stay in that box forever - LOL.

As many have said, these Coyote / 6R80's run well with just about any of the common gear ratios, so I'm staying with the gears that "feel" the most entertaining for daily driving duties (which is 95% of my car's use). 4.10's are staying in my car!

I still believe a 28" tall tire is better than a 26" tall tire at the track. Even if the OP is not having traction problems yet, a few more mods and/or better DA will change that in a hurry.
 

skaarlaj

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My original 3.15's are in a box in my garage. I believe they are gonna stay in that box forever - LOL.

As many have said, these Coyote / 6R80's run well with just about any of the common gear ratios, so I'm staying with the gears that "feel" the most entertaining for daily driving duties (which is 95% of my car's use). 4.10's are staying in my car!

I still believe a 26" tall tire is better than a 26" tall tire at the track. Even if the OP is not having traction problems yet, a few more mods and/or better DA will change that in a hurry.
Not to mention a 28" tire actually looks kind of short in the wheel wells on these cars. But yeah, the traction of a 28" over a 26" tall tire is pretty substantial in my opinion. My tire frying 04 Cobra I used to have struggled with 4 different sets of 26" tall drag radials through the years, then I finally tried a 28" and it actually allowed full throttle in 1st on the right surfaces.

Hey guys, I've got a 2012 Mustang GT. I race it at all my local 1/8th mile tracks but never take it to a 1/4. I'm thinking I could benefit from a gear change but not sure what gear to go with. It has the 6R80 transmission and here is my setup....stock 3.15 gear, boss intake manifold, BBK long tubes, off road X, flowmaster outlaw axle back, Circle D 5C converter, BMR tubular K member, lightweight radiator support, BMR upper/lower control arms, panhard bar, relocation bracket. The car shifts at 7700 rpm. The personal best for the car is a 1.6 60' and 7.57 @ 93 mph in 90+ degree weather with over 3500 DA. I run 15x3.75 front runners and 15x10 rear wheels with 275/50/15 Mickey Thompson ET streets (26" tall). I've been pondering going up to a 3.31 gear. I keep getting told to go to a 28" tall tire but I feel that would negate any gains that I picked up with a gear change. Please and thank you for the help! It's hard figuring out gearing on these A6 Coyotes. Here's a video of my second best pass...if you listen to the car it seems like it rolls through the traps at too low an RPM in 3rd gear....

https://m.youtube.com/watch?v=UTLr1Q5HfWc
From the on-line gear calculator I use http://www.rocky-road.com/calculator.html, running 93 mph on a 26" tire in third gear "1.52:1" your rpm's should be around 5750 if the converter is locked at this point which is kinda low for a boss intaked Coyote imo.

here's where I found your rpms to be with the following rear gears running 93 mph in 3rd gear.

3.31 = 6050
3.55 = 6485
3.73 = 6800
3.9 = 7100
4.1 = 7500

So if crossing the line at the highest rpm's possible is the be all end all most effective way to be quick, I'm guessing the 4.10's would be pretty good, and if you were a little off and happened to trap a little higher than anticipated, you could go with 3.90's to be safe, or use 4.10's and just swap to 28" tall rears to keep you from up-shifting into 4th. The 3.31 guys will never ever agree with this, but it would be pretty fun to find out imo. I've actually considered 4.30's, because at the top of the eighth I'm only running 80mph, and shifting right before the traps. Btw, if you use the calculator I linked, just plug a "1" into the transfer case ratio for accurate results.
 
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BigFudge

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I believe I may go with 275/60 Mickey Thompson ET Street Radial Pro's and a 3.31 gear. I've talked to two local guys recently and they both have 3.31 gears and 275/60 Pro's. One car on 93 tune has been 7.20's and the other on e85 has been 7.0's N/A. My car weighs less than both of these cars but they ran these times when it was cooler outside and with much better DA.
 

skaarlaj

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I believe I may go with 275/60 Mickey Thompson ET Street Radial Pro's and a 3.31 gear. I've talked to two local guys recently and they both have 3.31 gears and 275/60 Pro's. One car on 93 tune has been 7.20's and the other on e85 has been 7.0's N/A. My car weighs less than both of these cars but they ran these times when it was cooler outside and with much better DA.
damn that's gettin with the program!! They're doing something right.
 

Unreal

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Well then it does seam kind of magical then hahaha. I might have to install the 3.31's I took outa my manual car??? Did you pick up trap spped too or just 60' the best? If you don't mind me askin. I run in the eighth alot more than full quarter so 60' improvements benefit me much more than gaining trap speed.

Trap speed was all about the same. 3.55 had to shift one extra time which killed times. 3.15 just lazier off the line.
 

skaarlaj

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If for some odd reason I never end up supercharged, I might have to try something deeper like 3.73s, just because of my lack of air / power here in the mountains It seams like everyone usually traps high 80's-low 90's with non boosted Coyote Mustangs, and I'm about 10mph lower so in my case I might just benefit, and although that 5c helped my car drastically at the track, shifting into 3rd right at the stripe is pretty annoying.
 

Phil

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Another thing to note about these automatics, is when paired with the right converter, traction, they all seam to run pretty damn good, and a gear change can probably make the car feel alot different, but if tuned properly, you probably won't see much difference at the track imo. There's people that think that so and so's geared too low, and so, and so went faster with factory gears. I really think Five Oh Brian should swap in some factory 3.15's or 3.31s, make some hits at his local track, run the same number and put this to rest, hahaha!

agreed.
 

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