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4th Gear RPM With 4.10's On '13/14

9K views 28 replies 8 participants last post by  biminiLX 
#1 ·
I wanted to ask about 4th gear trap speed + rpm but then realized there's TONS of mods that would make that variable outcome change !! I have the VMP Stage 4 and the car makes 682rwhp on just under 16#'s boost with headers, 373's and the taller 305 Mickies out back . I plan on heading to the track soon and 4.10's are knockin at my door ! But...at the same time I'm considering trap speed vs rpm with 4.10 gears.

Could a few guys with 4.10's share where they're at in MPH in 4th gear at say 6200-6500rpm given your selection of rear tire and power mods ?
 
#2 ·
I might be able to check for you this week...But it will probably be very close to this chart...



I used the 3.90 gears chart since if you are running the taller MT's your 4.10's will be like 3.90's compared to this chart which is using stock tire sizing.
 
#3 ·
Wow Matt....that's an awesome chart. Much thanks !
 
#5 ·
Since he has 682 rwhp he is probably not going to trap near 140. I think with the 4.10's (and larger diameter tires) he should be near the optimum RPM crossing the 1320, without having to worry about the rev limiter.

The 3.73's combined with larger diameter tires are probably going to have him crossing the line at around ~5800 RPM, maybe less.

I know Birddoc recommends the 4.10s for the strip and 3.73s for the street. BJ I thought you did too?
 
#6 ·
I can't run 4.10s and 29's. I run out before I hit the stripe. It's about 137-38 for me but it was at 6700. 390's took it down a touch....around 6600@139 with the 29s. 373's will get me 140+ @6500-6600.

We run 2.73's in our GT drag car and cut 1.20's all day long. Traps 152-53.

I don't now what Mark is running for tire....but I guarantee you he isn't dealing with a stock redline. That's the big diff.

GWIW, I'm a little over 800 at the tire. About 820. Car is 3950 with me in it. Marks weighs a lot less.
 
#7 ·
Interesting...

I guess I thought the difference would also be in the transmission. 2013/2014 have taller ratios, so by the time he is in 4th gear he should further down the strip, is that correct?

BiminiLX has 4.10's and is not running out of rev limit before the line in his 2014 GT500. I think he ran an 11.01 with just 4.10's, drag radials, and a tune.
 
#10 ·
Just responded with this in the other gear thread:

"Gotta remember the '13-14 have different trans gear ratios with a 2.66 first and 0.50 6th; also we have Ford GT cams and higher peak power (6600rpm range) with a 7000rpm over-rev.
It's there for a reason, it will run faster using that extra RPM and higher trap RPM with 4.10s

As long as you are willing to run a taller (28"+) drag radial, the 4.10 is the best drag gear hands down.
It is also the best on the street IMO--immediate boost and acceleration out of boost for these heavy cars, plus 80mph at 2000rpm, win/win.

One rule of thumb is 4.10 under 800rwhp, 3.73 over 800rwhp.

Well, last year I had my rear fully built and went with 3.73s as I plan to go over 800rwhp.
The gears whined so its just an excuse to swap back to 4.10s because I REALLY liked the 4.10s more, better on the street, highway and track.
My car with 4.10s out trapped the 3.73s (138 vs 136mph), it just wanted to pull harder at the stripe."


To be more specific, with only a tune, 4.10s and 315/35/20 NT05Rs I trapped less than 6500rpm at 128.8.
Not sure on power level there, but later the next year, I had mods and trapped 137.8mph at about 6500rpm with 28" M&H 325/40/18s.
Not sure on power there but AFTER that run I swapped on a ported blower and got 755rwhp.
My goal is to trap 140-145mph and I just bought 29.9" tall 325/45/18 Hoosier DRs for the expected E85+ported blower+2psi (upper pulley).

Unless you plan on modding hard core to over 800rwhp, my strong recommendation is 4.10s and taller tires (over 28").

Good luck in your choice.
-J
 
#8 ·
All Tremec TR6060s have a 1:1 ratio in 4th gear. Only variables are tire diameter and gear ratio. Plugging the un-inflated tire diameter is going to give you a different result than using tire revolution per mile data. If you want to use one of these calculators, take a measurement from the pavement to the center of the rear tire under the weight of the car and double it. That will get you the right result.
 
#9 · (Edited)
Not positive, but I would think the un-inflated numbers, plus air pressure, minus the weight of the car, should still be very close to the charts when moving at speed in 4th gear across the stripe. I guess a huge variable could also be what air pressure they are running at.

I haven't read of anyone hitting the rev limiter in a 13/14 with 4.10's in the 1/4 mile with basic bolt on's (700rwhp'ish). Maybe I am wrong, wouldn't be the first time.

Also have you guys seen this thread?

http://www.fordgt500.com/forums/showthread.php?t=113049&page=2

He hit a recorded 153 mph with 4.10's at 4th gear red line in a half mile event. Granted the exact distance or speed measurement could be off, but doubt it is 13 mph off.
 
#11 ·
What RPM do you trap now?
I'd run it as is with the 3.73s, but I can bet you'll want 4.10s.
The car will run harder if you can trap 65-6800rpm.

Now the rods on the other hand.....:boohoo:
There's a reason I'll be swapping cams and rods this winter, I want to use the power at the strip and that means 7000rpm traps--not sure how long the rods will like that.
-J
 
#25 · (Edited)
I can share my recent experience with 4;10 gearing. I have a 14GT500 with about 725 at the wheel, perhaps 10 or 15rwhp more today ( just installed blower elbow). After chatting with Jam and Bimini I swapped in the 410 and use either my Nt05R ( 28.7 dia) or Et streets (apprx the same DIA).I ran at Milan dragway, the conditions were 92 and humid, but good bite. I launched the car with the et streets with 1.71 60 ft and hit my rev limiter before that traps. Be aware, I moved my limit to 6500, where it was formally at 7100. I am getting gun shy on high rpm. I lifted when it hit the limiter and ran 10.854 at 130.9 mph. I used to run 133 with my 355 gears.( different day and weather) The 373 vs 410 discussion has merit, but I LOVE the 410's for all around better torque. I mainly street race and not tied to pure 1320 foot.

You will likely have to up your rev limit to over 6500 or run taller tire to utlize 410 gears at track. IMO. I am keeping my 410 for all around use. I hope this helped.
 
#26 ·
I will check my rev limiter again to confirm, while I have never had any issues the 7000 rpm concerns me and my dyno chart wasnt much better at the higher range, so I changed mine with sct tuner. I check the limit. I do recall It pulled 1.2 G , which is my best and I attributed to better tire and gear for me
 
#27 ·
MPH is little harder to calculate with a drag radial because the loaded radius will change with air pressure. But using the rev per mile data on my street tires, which are the same diameter, I get 131 mph @ 6,500 rpm with 4.10s. 3.90s would be a good compromise at 138 mph.
 
#29 ·
As Dodgeboy mentioned, the 4.10s are also best for making this car fun out of boost, it improves the car dramatically on the street and doesn't suffer on the highway.
Several taller tire options also, I have 325/45/18 nearly 30" drag radials in the garage I'm dying to try.
Dodgeboy--can you post the Dyno graph? I will later once on my laptop but I peaked at 6600rpm.
-J
 
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