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Discussion Starter #1
So I know everyone says keep the 315 or swap to 331 on the auto with 1/4 mile performance in mind. My question is this...My mods are Boss intake, JLT, 85mm TB, Long Tubes and full off road x-pipe and axle back. Now I also have a circle D 5c converter (4200ish stall). AED tuned I do shift at 7500 to take advantage of the Boss Intake. Dont feel comfortable taking it any higher on a stock bottom end as I need the car to last not chuck a rod lol. Now my car came from the previous owner with 373's. I picked up a set of 331's a while back form a member here but haven't put them in yet. Got a buddy who has built some very quick Fox bodies and sn95 cars....however we all know the 6R80 is a different animal as far as gearing. Right now I can dead hook the car and pull the front skinnies right off the street with the 373 but I am going into 4th around probably the 1000' mark roughly. So my question is with my mods including the converter and higher shift points should I still go with the 331 or leave the 373? Will I pick up any ET gains going to the 331 with my mods? I have searched a lot but all the recommendations never include a converter and boss combo it seems like. Lets hear form the experts who have done it. No theories pls.:headscratcher:
 

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You didn't post your current times but yes you will gain simply because that extra shift into 4th is slowing you down. You will be able to carry 3rd out all the way. Also you didn't say if it mattered or not but in the end you'll get better gas mileage and less wear and tear. Nothing wrong with that.
 

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You didn't post your current times but yes you will gain simply because that extra shift into 4th is slowing you down. You will be able to carry 3rd out all the way. Also you didn't say if it mattered or not but in the end you'll get better gas mileage and less wear and tear. Nothing wrong with that.
Scottmach The King of Automatic Mustangs!
 

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I wouldn't go that far but I'm smart enough to realize the ones who've been down this path and then had the data to back it up. And then follow in their footsteps to see for myself. Kris Danner would be the one I would pay most attention to.
 

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I wouldn't go that far but I'm smart enough to realize the ones who've been down this path and then had the data to back it up. And then follow in their footsteps to see for myself. Kris Danner would be the one I would pay most attention to.
Kris knows his ****, and he is also not scared to drop the money to try something new knowing it could be worse then what he had. I think my drag racing days are over in my 5.0l, but I may go buy a hunk of **** fox body or something and drag race it.
 

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Discussion Starter #6
Dunno current times yet. Tracks still closed. Have one of them G-tech deals that's proven to be pretty close to accurate in the past and the speed is 120-121mph. So, even a quick shift in an auto will slow it down then is the consensus and been proven?
 

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So, even a quick shift in an auto will slow it down then is the consensus and been proven?
Yes. What's better, crossing in 3rd at the top of your power band or shifting into 4th and dropping out of your power band as you cross? Seems pretty simple to me.
 

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Discussion Starter #8
What of the argument that the 373 gets you into that poweband quicker? Not arguing whays proven but explaining to a buddy why the 331 will be beneficial over the 373 and that's brought up also.
 

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Depends on how fast the car actually is. Since you don't want to go over 7500, you might still run out of gear with 3.31. To keep it in 3rd, 3.15 would be the safe bet, and yes I expect it to be a hair quicker than shifting to 4th.
 

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Discussion Starter #10
Depends on how fast the car actually is. Since you don't want to go over 7500, you might still run out of gear with 3.31. To keep it in 3rd, 3.15 would be the safe bet, and yes I expect it to be a hair quicker than shifting to 4th.
As for how fast you'd be the guy to probably guess the closest, its a loaded model with leather, shaker and glass roof, no nav no heated seats only pwr drivers seat only weight out is spare tire....mid 11's hopefully maybe a bit better? Well how risky would it be if I push it past 7500 in 3rd just through the traps, like whats the danger-zone on a stock internal engine like for the rods? Valve springs?? I came from the LS1 world where anything past 6800 you better rod bolt it or time is ticking... I do DD this car during the summer so would def like to keep in in one piece..331 I already have is why I was going to use it. I seen no reason not to have the best of both worlds on these cars, better mpg, faster? Works for me.
 

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As for how fast you'd be the guy to probably guess the closest, its a loaded model with leather, shaker and glass roof, no nav no heated seats only pwr drivers seat only weight out is spare tire....mid 11's hopefully maybe a bit better? Well how risky would it be if I push it past 7500 in 3rd just through the traps, like whats the danger-zone on a stock internal engine like for the rods? Valve springs?? I came from the LS1 world where anything past 6800 you better rod bolt it or time is ticking... I do DD this car during the summer so would def like to keep in in one piece..331 I already have is why I was going to use it. I seen no reason not to have the best of both worlds on these cars, better mpg, faster? Works for me.
Personally, I'd do the 3.31 and if you get fast enough and have to stretch it some past 7500 through the traps that is fine. In the past I've taken them as high as 7900. Last weekend at the TX mile I had a stock engine with a TVS doing 7600+ out the back, that's a whole lot more time at high RPM than any quarter mile ever will be, plus it's blown so under much more strain.
 

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Discussion Starter #12
Personally, I'd do the 3.31 and if you get fast enough and have to stretch it some past 7500 through the traps that is fine. In the past I've taken them as high as 7900. Last weekend at the TX mile I had a stock engine with a TVS doing 7600+ out the back, that's a whole lot more time at high RPM than any quarter mile ever will be, plus it's blown so under much more strain.
Good point. I will do that then. Whats your opinion on the factory trans and not needing an aftermarket cooler? With my 5c I had planned a cooler but everything I read said no need. This just seems really odd to me. Whats your experience on the stock 6r80 and a bigger converter, get an aftermarket cooler or the stock setup really is that good?
 

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No cooler is needed in these cars. The cooler as well as the lines itself are HUGE.
 

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Discussion Starter #14
No cooler is needed in these cars. The cooler as well as the lines itself are HUGE.
Cool, thanks for the reassurance. Is there a way to see trans temp on the SCT X4?
 

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Not to TJ but this doesn't make sense to me........ I know the 6R80 has the 4.17 or whatever deep 1st gear ratio, but wouldn't it be more beneficial to cross the traps in 4th instead of 3rd? With my 5R55, I have a 3.22 1st gear and combined with my 4.10's, this gives me a tq multiplication of 13.2. With the 6R80, it's a 13.1 with 3.15 gears, 13.8 with 3.31 gears, 15.5 with 3.73 gears and 17.1 with 4.10's. A 4R70W on the other hand, has about the same 1st gear as I do 2nd, 2.84. So even with 4.10's, you only get a tq multiplication of 11.6. So why is it more beneficial to run such numerically lower rear gears behind a 6R80 vs something like a 4.10? 4th would top out @ 125mph with a 275/50R15 Drag radial or 26" slick with 4.10's and 137 with 3.73's. I mean, it's an automatic. It's not like it take any long period of time to complete a shift. Someone help me out here........lol.
 

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Not to TJ but this doesn't make sense to me........ I know the 6R80 has the 4.17 or whatever deep 1st gear ratio, but wouldn't it be more beneficial to cross the traps in 4th instead of 3rd? With my 5R55, I have a 3.22 1st gear and combined with my 4.10's, this gives me a tq multiplication of 13.2. With the 6R80, it's a 13.1 with 3.15 gears, 13.8 with 3.31 gears, 15.5 with 3.73 gears and 17.1 with 4.10's. A 4R70W on the other hand, has about the same 1st gear as I do 2nd, 2.84. So even with 4.10's, you only get a tq multiplication of 11.6. So why is it more beneficial to run such numerically lower rear gears behind a 6R80 vs something like a 4.10? 4th would top out @ 125mph with a 275/50R15 Drag radial or 26" slick with 4.10's and 137 with 3.73's. I mean, it's an automatic. It's not like it take any long period of time to complete a shift. Someone help me out here........lol.
Big reason is you can wind the Coyote out to 7800 in 3rd and trap the same 125, The 3.31's and the same 1.54 3rd gear the Coyote will pull harder than the 5r with 4.10's in 4th.
 

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Not to TJ but this doesn't make sense to me........ I know the 6R80 has the 4.17 or whatever deep 1st gear ratio, but wouldn't it be more beneficial to cross the traps in 4th instead of 3rd? With my 5R55, I have a 3.22 1st gear and combined with my 4.10's, this gives me a tq multiplication of 13.2. With the 6R80, it's a 13.1 with 3.15 gears, 13.8 with 3.31 gears, 15.5 with 3.73 gears and 17.1 with 4.10's. A 4R70W on the other hand, has about the same 1st gear as I do 2nd, 2.84. So even with 4.10's, you only get a tq multiplication of 11.6. So why is it more beneficial to run such numerically lower rear gears behind a 6R80 vs something like a 4.10? 4th would top out @ 125mph with a 275/50R15 Drag radial or 26" slick with 4.10's and 137 with 3.73's. I mean, it's an automatic. It's not like it take any long period of time to complete a shift. Someone help me out here........lol.
The answer is there via mathematics, if you have all of the correct inputs. I believe if you look into moment of inertia and possibly angular momentum you will find the answer there. However, does that really matter? In the end what we really want is the car to be quicker, we aren't necessarily looking for the formula that proves why. Time and again these cars have proven themselves to be quicker with less gear. I'm especially glad to see some of the forced induction cars finally catching on to this, as it only makes sense that if an NA car can haul ass with so little gear, forced induction is going to do it with even less. Those guys are now trying to find old 80s pickup truck rear axles so they can rob the 2.47 ring and pinions out of them. :)
 

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Maybe they seem quicker because of others not being able to hook with 4.10's out of the hole where using a gear that maximizes 3rd gear is easier to get out of the hole? By what you are saying, you 5.0L guys would be even faster yet if you switched to a Glide. I'd like to see a heads up comparison of a car that has all the typical bolt-ons, suspension, tune and a set of 3.15-3.31 gears vs 4.10's to look at the 60ft and rest of the track data. I know if the car is making the same hp, the trap speed will be nearly identical. I would still think if the car had 4.10's and hooks good that it would be quicker because of the much harder launch. I dunno, I'm just learning about these cars. They seem to be contradicting everything that us drag racers have been doing the past 60 or so years.
 

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While it may seem contradicting to what worked in years past, it's being proven time and time again now these cars do not need the steeper gearing others needed. And do not respond to them.

Mike Rousch of Mid Atlantic Performance did same day testing with 3.31's and 4.10's and the 3.31's came out on top. There are many more examples out there.
http://www.s197forum.com/forum/showthread.php?p=1991698#post1991698

Some guys with 4.10's will shift into 2nd before they even hit the 60' mark. That's just not being productive.
 
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