Need Help with gear ratio's for S4

DOINSND

DOINSND

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I don't know what gear ratio's to get.

Ive been wanting to pull the trigger on a S4 for a while. Ive been babying a 2D. Now with prices going up in August its time.

I have a BFD Super Sport (Revo) two seater mid engine around 2200Lbs. Im running a Alper built LS6 383 Stroker twin turbo with around 10psi of boost.

Have 33's going to switch to 35.5 

TIA

WVCH6473.jpeg

 
What ratio is in the 2D, you have ran the fastest at Dumont for a couple of years now, what do you think about the gears you have now, 

 
I have a 2 seat mid eng Prowlers with a LSA at 14psi, E85 and sequential PBS. 2500lbs with me in it. It has the big Dunesport tire so 34" tall.

Gears are 4.57RP 1st 2.91, 2nd 1.93, 3rd 1.44 and 4th 1.14. I ride the glamis dunes in 3rd mostly 2nd for the small stuff and 4ft on the really big stuff. It goes way faster than I need in 3rd when I'm in the dunes.

The 35.5 will not be kind to your S4 IMHO    

 
As Jason already said, if you like the gears in your current 2D, then there is no reason to change them, unless you are also changing something else that would affect them, like going to a different tire or adding power.

If you don't know what gearing you had in your 2D, then it would help if you knew what kind of speeds at what RPM you have been getting already, then you can at least make an educated decision using our gear ratio calculator to get close.

If you are starting from scratch and have no idea, then you have to think about what speeds you want to get out of each gear. The 2.91x1.93x1.44x1.14 set is the most common set in use, and seems to work for 80% of the people running this set.

Most people will never need more than 75-80 MPH at the top of 3rd gear in the dunes, 4th gear is just the extra gear for the flats when needed. If you are running the drags, then you would want to start with what top speed you want and choose the 4th gear that will get you that speed at the top of the RPM, then split the 1st-3rd gear evenly using the "percentage of pull" box on our calculator chart.

 
I have a Su LS3 mid engine that came with a 2D, Gearing, 5.43 R&P 1st- 2.90 2nd 1.86, 3rd 1.39, 4th 1.14, changed to a PBS 4:57 R& P, 1st 4.57, 2nd 2.14, 3rd 1.67, 4th 1.32, it has 35's #2 cup, I run Dumont 3rd & 4th all the time.

I'm just finishing up going through a S4S that has 4:57 R & P, 1st 3.18, 2nd 1.93, 3rd 1.56, 4th 1.20. This came out of a Buckshot midengine, I'm changing it to bigger trans right now. If you're interested going to put it up for sale probably next week if you're interested let me know

 
Be prepared to wait awhile for a new S4. Final gear ratios might be dictated somewhat by what gears, R&P are available.

 
Last edited by a moderator:
  • 1st    2.91
  • 2nd  1.86
  • 3rd   1.44
  • 4th   1.14

Ring and pinion is a 4.88 and 35.5 tires 

But i dont think they make that second gear anymore, so you might be stuck with a 1.93

So for my Extra gears i have a 1.93 and 3rd is a 1.51 and i have a 1.44 spare, then a 1.21 4th spare,   

What makes me run a lower 3rd and 4th now is i have a DRY SUMP so i can bring the car up to 7800 rpm, 

 
Last edited by a moderator:
Don't know if Weddle updated the other R&P's, but the 4.63 has the increased pinion depth.  

Should give more longevity.

 
Going to run the flats at 70mph+ for extended periods of time?  If so, gearing 4th to hold less than 3500rpm (1:1 ratio) at that speed would be helpful for oil temps.

 
For Dumont and Idaho, and the Size Turbos and Engine combo, i would go with 

36'' Blaster 2 cut, 

  • 4.63 RP
  • 1st 3.09
  • 2nd 2.08
  • 3rd 1.59
  • 4th 1.26

That should pull hard up comp and get you to 116 mph to North Pole 

 
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