4L80E with Ford 9" gear ratio?

[Blevinator]

68 Camaro
LS3 motor (6500 rpm redline)
4L80E trans
Ford Fab rear end
335/18 tire
Should be at 500 na-600-650(turbo'd) at the rear wheels
Contemplating between 3.25 and 3.50 gear ratios
Street Car
Thinking a lower gear ratio will work better with my hp goals?

[TheJDMan]

What is the OD ratio of that transmission? Off the top of my head, I'm thinking more along the lines of 3.73. You need to find a good gear ratio calculator.

[Schwartz Performance]

You will have better results with the lower number gear being a turbo car with that kind of power. But given that it’s a 4L80 which has a 2.48 first gear.. I’d go with the 3.50.
If it was left n/a I’d go with a 3.89.

[andrewb70]

With that kind of power, I would do a 3.25 gear. If you have a bit of a stall, it will flash nicely of the line and make up any deficiencies. With the 3.25 gear and a 335/30-18 tire, you will run 2200rpm @ 75mph on the highway, which is about right, at least for me.

Andrew

[mean buzzen half dozen]

I have 3.5's for my same set-up as yours, but mine will have a turbocharged inline 250 six cylinder.

[Blevinator]

What is the OD ratio of that transmission? Off the top of my head, I'm thinking more along the lines of 3.73. You need to find a good gear ratio calculator.

OD is .75

[Blevinator]

What I am trying to avoid is the car just sitting there spinning at the line
Pretty sure my old 2001 Trans Am had 3:42’s
It had about 432 hp at the rear tires
On brand new street tires, it would spin the tires almost off the rim, unless I launched at a very low speed and then worked my way into the throttle
With that car, I had a T56 transmission
To be fair, I only had the stock suspension on that car which was pretty poor
This car has a billet g link setup
I also have a 2500 stall converter
First gear has a 2.48 ratio on the 4l80
Final drive is .75

[andrewb70]

Stock 4th gen f-bodies had 3.23 gears with the 4L60 and 3.42 gears with a T56. As I said, if it was my car, I would to 3.2x gears.

Andrew

[Blevinator]

Sounds good. I read an article that said it could depend on the stall converter I am using along with the power band of the motor and the camshaft as well
I am using the East Coast supercharging small blower cam
I am pretty sure the power band on the cam is mid to high range, so may want lower gears off the line
Traction will be the main concern for me anyway

[andrewb70]

What are the cam specs?

Andrew

[Blevinator]

Mid 230's, 588 lift on a 117 LSA
Although on the Internet I hear 115 LSA
ECS spent years of R&D and will not release the exact specs
I am going to call them tomorrow to find out where the cam power range is

[TheJDMan]

I have a G-link rear suspension and it is not great with forward bite. I can pretty much spin the tires at will. On a road course I have to be careful with throttle application on corner exit to avoid tire spin.

[Blevinator]

Sorry to hear that the G link is not good at controlling forward spin
I was originally referred to Savitsky who told me that it was the best thing to control forward spin?
May end up going with a 3.25 anyway

[andrewb70]

Mid 230's, 588 lift on a 117 LSA
Although on the Internet I hear 115 LSA
ECS spent years of R&D and will not release the exact specs
I am going to call them tomorrow to find out where the cam power range is

That's a pretty healthy cam. I wouldn't be so worried about the power range as I would be about low RPM stability. Stock cams are very happy pulling a load on the highway at 1600-1800rpm. Bigger cams, not so much.

My guess is that this cam should be fine around 2200rpm, which is what it would be turning at 75mph with 3.25 gears. Then again I tend to pick gear ratios based on good street and highway manners, and not so much for ultimate performance, although sometimes those two things end up being the same.

Andrew

[Schwartz Performance]

With that kind of power, I would do a 3.25 gear. If you have a bit of a stall, it will flash nicely of the line and make up any deficiencies. With the 3.25 gear and a 335/30-18 tire, you will run 2200rpm @ 75mph on the highway, which is about right, at least for me.

Andrew

4L80e is a .75 OD, Tremec calc says 2,354 RPM at 75mph. What were you going off of?

3.00 gear would be 2,173 rpm.

However with the 4L80e tall first and second gear (compare to a 4L60 or even a close ratio T56)
it's going to "act" like you have a taller rear end gear in comparison.

-Dale

[andrewb70]

4L80e is a .75 OD, Tremec calc says 2,354 RPM at 75mph. What were you going off of?

3.00 gear would be 2,173 rpm.

However with the 4L80e tall first and second gear (compare to a 4L60 or even a close ratio T56)
it's going to "act" like you have a taller rear end gear in comparison.

-Dale

Dale,

I was using a spreadsheet, but I just realized it has an error. After fixing it, I am getting 2317rpm @75mph and 2189@75 with a 3.00 gear.

Andrew

[Barrrf]

I dont know man. I had a 3.31 rear gear with my 4l80e and I was NOT happy with the acceleration of my 6L build and a 3200 stall. When I jumped up to 3.73 I could finally see the light.

[andrewb70]

I dont know man. I had a 3.31 rear gear with my 4l80e and I was NOT happy with the acceleration of my 6L build and a 3200 stall. When I jumped up to 3.73 I could finally see the light.

Did you have a turbo?

Andrew

[Barrrf]

Did you have a turbo?

Andrew

Good call mod. I do NOT have a turbo.