10R80 + 4.09 Gears

[NianJay5OH4]

I currently have an ALL stock A10 '19 GT equipped with factory 3.15 gears. I recently posted a thread about going NO2 but after reading different opinions I think all stay NA until I can get some boost money. I see NA 10R80's going 10s with basically a gear swap (4.09), LTH and E.
As soon as my warranty is over with, of course I'll be doing a 3" cat delete (all ready have cat deletes because I bought them for my 16GT) and E85 (may or may not have my manifold ported).

My question is does anyone have experience with 4.09 gears with the 10R80?
How is the 10R80 + 4.09s on the freeway? (RPM at interstate speeds 75mph-85mph)
What would my top speed reduce too? (I believe I can hit 154mph with 3.15 on stock 18s)
For track days I was looking at 275/40-17 Mickey Thompson ET Street R tires which are basically 26" tall. Would 26" tall tires work well with the 4.09 swap for 1/4 mile racing?

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[1MEAN18]

I currently have an ALL stock A10 '19 GT equipped with factory 3.15 gears. I recently posted a thread about going NO2 but after reading different opinions I think all stay NA until I can get some boost money. I see NA 10R80's going 10s with basically a gear swap (4.09), LTH and E.
As soon as my warranty is over with, of course I'll be doing a 3" cat delete (all ready have cat deletes because I bought them for my 16GT) and E85 (may or may not have my manifold ported).

My question is does anyone have experience with 4.09 gears with the 10R80?
How is the 10R80 + 4.09s on the freeway? (RPM at interstate speeds 75mph-85mph)
What would my top speed reduce too? (I believe I can hit 154mph with 3.15 on stock 18s)
For track days I was looking at 275/40-17 Mickey Thompson ET Street R tires which are basically 26" tall. Would 26" tall tires work well with the 4.09 swap for 1/4 mile racing?

Take a look at Steeda and their Silver Bullet build. I followed their lead on a lot of your questions (common stuff) except I stayed with a 19" drag radial (305/35/19 Nitto 05R which are 27.5" tall) out back because my '18 is mostly a street car and I don't like the way drag pack wheel combo's look on the street (I prefer a much larger wheel because 15" wheels on these cars with a bias ply thick aspect ratio looks downright silly in my opinion on a street car). My front runners are 18" Recluse 95's (also used by Steeda) and are wrapped in M/T skinnies that are 28" tall. Would I ever swap my 3.55's for 4.09's? Probably not. But a 3.91 torsen diff is on my to do list because I have no plans to boost my coyote at this point. A stall speed from Circle D will give you more performance at this point than the gears will, and if you are likely to go boost anyways, your gonna want to keep that 3.15 gear, if you are gonna eventually boost the car, a 3.55 gear would be the highest numerical gear I'd chose to use. You also didn't mention any suspension modifications...well that is a piece of the puzzle on these cars that is a must do if you really wanna lower your times. Look into a Steeda stop the hop kit and add in the drag racing rear sway bar and lower the car with a set of weight transferring struts up front and you'll get as much from that or more than any gear swap would ever do for ya.

 

[NianJay5OH4]

I'm currently lowered on Eibach pro kit and I was going to do the BMR cradle bushing lock out and the BMR IRS subframe support brace. Boost is down the road from now so I'll keep the 3.15s in a box somewhere. Ill only have the radials on during track days, I daily on 20x10s
This is where I got the idea of 4.09. I don't know if I want to add a stall on a DD car
https://www.steedablog.com/2018/02/27/steedas-lethal-na-silver-bullet-2018-mustang-gt-first-10s/

 

[1MEAN18]

I'm currently lowered on Eibach pro kit and I was going to do the BMR cradle bushing lock out and the BMR IRS subframe support brace. Boost is down the road from now so I'll keep the 3.15s in a box somewhere. Ill only have the radials on during track days, I daily on 20x10s
This is where I got the idea of 4.09. I don't know if I want to add a stall on a DD car
https://www.steedablog.com/2018/02/27/steedas-lethal-na-silver-bullet-2018-mustang-gt-first-10s/

Steeda also stopped using the 4.09 gear once they realized the 1-2 shift was occurring BEFORE the 60 ft mark making the 4.09 gear a bit too aggressive and actually raised the 60 ft times instead of lowering them. The truth is in the details. I'd do full suspension first and learn how to launch your car to get repeatable numbers before I'd ever consider changing that 3.15 gear. A stall will do more for your car on drag radials than a gear will, but its far more expensive, and of course requires taking the transmission out, and having the tune adjusted.

 

[5.oh]

Fastest na car is running 3.15’s. Started with 3.55, swapped in 4.09 went slower then worked back to the 3.15’s

 

[drive_55_not]

Fastest na car is running 3.15’s. Started with 3.55, swapped in 4.09 went slower then worked back to the 3.15’s

^^^ This,, These A10's do not need that much gear,, Weight loss and an aggressive E85 tune will get you into the low 11's. MY fat a$$ non drag mode car's been 11,67 @122 with E85 LT's and the stock intake.

IIRC he's running 3.15's..

https://www.mustang6g.com/forums/threads/blue-18-goes-10-53-at-132-44.132310/


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[Kermitz]

A member here by the name of Lockdown18GT is running 10's NA. He went from 3:15 to 4:09 and then back to 3:15's. Can't remember why exactly. There's a few posts about it if you search.

 

[Rjames18]

Dont go to 4.09's... Stay with 3.15's

 

[Marketplaza]

I just had 4.09 put in my 19 gt manual. I have the Lund e85 tune and after install I went into limp mode. My rear view camera stopped working, rev matching, my trac control and cruise control. It’s Friday so Lund was closed by time I emailed them, I just never heard of this happening on a manual gear swap. This is very frustrating.

 

[stang1087]

@Marketplaza
My first thought is you have some kind of wiring problem, like a damaged/disconnected harness or blown fuse. I think rev matching is dictated by gear selection. I think the reverse switch is also in the transmission and since, to my knowledge, traction control doesn't work in reverse I'd take a look at the transmission harness to see if was disconnected for some reason.

 

[Marketplaza]

@Marketplaza
My first thought is you have some kind of wiring problem, like a damaged/disconnected harness or blown fuse. I think rev matching is dictated by gear selection. I think the reverse switch is also in the transmission and since, to my knowledge, traction control doesn't work in reverse I'd take a look at the transmission harness to see if was disconnected for some reason.

Thank you for the info. I’m going to bring it back to the shop on Monday and have them look at it. There the ones who caused it so hopefully they fix it. I sure paid enough

 

[Kermitz]

I just had 4.09 put in my 19 gt manual. I have the Lund e85 tune and after install I went into limp mode. My rear view camera stopped working, rev matching, my trac control and cruise control. It’s Friday so Lund was closed by time I emailed them, I just never heard of this happening on a manual gear swap. This is very frustrating.

I think it's tune related. Probably a strategy issue. Easy to fix.

 

[Marketplaza]

I think it's time related. Probably a strategy issue. Easy to fix.

I spoke to Lund and they said it’s a bdm issue not a pcm and a tune has nothing to do with the gears.

 

[Kermitz]

I spoke to Lund and they said it’s a bdm issue not a pcm and a tune has nothing to do with the gears.

Interesting. So you were already tuned prior to the 4:09's?
I had some problems after installing a tune once.
Loss of rev match, loss of rear view camera and a wrench light with codes P086E & P095B.
Tuner tweaked the file with a different strategy and it was perfect after that.

 

[Dominant1]

Looky what i just got to replace my 3:55’s on my boosted gt./cs i just finished painting it.
3:15’s:

https://ibb.co/ns4Ystq

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