NA LS gear ratios

Jtmoney714

Jtmoney714

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I feel my s4 is geared too tall. And going up in tire size to an 36 blaster exacerbated that feeling. It’s great on flat ground but it will chug a little at times in the tight steep stuff. With 14.50x17 worn set dune sports I would be able to get on top of the tire no problem. Now not so much. I’m estimated 650-675hp. So guys with similar power what ratios have you found to work or not work? 

 
What are you current ratios?

What R&P?

Is that crank HP or wheel?

 
This is for my 468 NA

I have a 1.50 Third brand new for a discounted price if someone wants one,  

I do my own trans work so try to keep my hears on the shelf,  or trade for a 1.44 if brand new 

1.50 third might be a little better for say a 416Ci

 
J Alper said:
This is for my 468 NA

I have a 1.50 Third brand new for a discounted price if someone wants one,  

I do my own trans work so try to keep my hears on the shelf,  or trade for a 1.44 if brand new 

1.50 third might be a little better for say a 416Ci
Click to expand...
Mine is a 427. So close enough. I think you’re right about a 1.50 3rd. I think I want top speed to be about 110ish. 

 
Can’t click down a gear, or is even 1st too steep?

 
Not quite an apples to apples comparison,  I'm still on 33" tires. But maybe a little help. When I bought my car it was geared 4.86 r&p then 3.09 2.08 1.59 1.26

I always felt the car was geared to low in 3rd and 4th. top speed was 99 bouncing off the rev limiter.  

I finally pulled the trans after 5 years, changed 3rd to 1.50 and 4th to 1.14

I didn't want to make to large of a change at once, I printed out 4 different ratio options using the weddle calculator, and this seemed like a good set up. 

I ran the car once with the new gears, for about 15 minutes, felt great, then the engine locked up 😔 

 
Jtmoney714 said:
The trans gearing is unknown. Crank hp. Made 560 to the wheels. 
Click to expand...
Copy that.

I did 540 to the ground.

Here is my gearing.
I run 33" Blasters for what it is worth.

I can run Glamis all day long in 3rd and 4th.  Never go to 2nd unless it is a super sharp turn.

4.63

2.91

1.93

1.44

1.14

 
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Jtmoney714 said:
Mine is a 427. So close enough. I think you’re right about a 1.50 3rd. I think I want top speed to be about 110ish. 
Click to expand...
The S4D is a huge ring and pinion so i did a 4.88 RP,  and sometimes i feel 3rd is a little tall   4.88 x 1.50 - 7.32 finial drive,  i would do a 4.68 with a S4 to keep the pinion bigger,  

4.63 x 1.56 - 7.22  

I think a 4.63

  1. 3.27
  2. 1.37
  3. 1.56
  4. 1.20

If the motor is stroked with a cam and heads,  if the motor is pretty stock than your on target with the other ratios you picked,  

Looking back, i never use 1st gear unless i am at vendors in Dumont, but now you can not drive through the vender strip.   i want it to be as easy as possible to get it in the trailer, think i will go super low with 1st gear on the next go around,  

I need a 6 speed LOL,  Granny Low with a overdrive, LOL 

 
Looney Duner said:
Not quite an apples to apples comparison,  I'm still on 33" tires. But maybe a little help. When I bought my car it was geared 4.86 r&p then 3.09 2.08 1.59 1.26

I always felt the car was geared to low in 3rd and 4th. top speed was 99 bouncing off the rev limiter.  

I finally pulled the trans after 5 years, changed 3rd to 1.50 and 4th to 1.14

I didn't want to make to large of a change at once, I printed out 4 different ratio options using the weddle calculator, and this seemed like a good set up. 

I ran the car once with the new gears, for about 15 minutes, felt great, then the engine locked up 😔 
Click to expand...
A lot of guys want to “dune in 3rd”

Others don’t mind shifting here and there.

All in preference. I feel like a car geared to 99mph on the rev limiter is really a car with 2 1sts and a 2nd/3rd. 99 in 4th would suck on sand highway. 

 
This is all very good info and very helpful. Hopefully more will chime in too. 

 
IMO -  the right way to gear a car is the know the power curve of the engine (based mostly on cam and head combo and of course cubic inch)  - this is easy see with Dyno graphs and you set the gear ratios to keep the engine in the power curve also called the torque curve of the engine.   Not all  of us have Dyno graphs in front of us, so  without that its still  pretty easy to do even if you don't know the specs or have the dyno graph -  just drive the car in 3rd or 4th and watch the tach and feel where it pulls the hardest.  thats gonna give you a good idea even if the Pull is not great- you will know where the most power is made.  Most good sand car engine builders doing NA will make this between 2500 and 5500 because the X-over of TQ to HP happens on all engines at 5252 RPM and the theory is that once the HP starts top take over the car is already moving enough that TQ multiplication is not needed. TQ moves the mass afte rall and its the power you feel when accelerating.

Once you know the range - you use the Weddle calculator to set the shift points, and while the gear ratios are limited that we can buy  you can come pretty close to perfect, just remember to keep the RPM drops between gears as close to 500 RPM- 750RPM as you can and if the engine builder did not get stupid with too big cam  (not good for duning)  the car will perform excellently.

This is not my "concept" its how most car manufacturers do it and how just about every race does it.  How most duners used to do it is they had e a "buddy" with a similar car and engine combo that "worked" , and just copied their ratios .... That worked OK when most cars had the sme CBM Redline or Turnkey setup, but with so many different combos out there  - its not the best way... And don't forget, weight (car, axle, CV, and brake rotor size)  matter as much as tire size  and how tight the suspension is.

Just my 2 cents  ...

 
Fullthrottleguy said:
IMO -  the right way to gear a car is the know the power curve of the engine (based mostly on cam and head combo and of course cubic inch)  - this is easy see with Dyno graphs and you set the gear ratios to keep the engine in the power curve also called the torque curve of the engine.   Not all  of us have Dyno graphs in front of us, so  without that its still  pretty easy to do even if you don't know the specs or have the dyno graph -  just drive the car in 3rd or 4th and watch the tach and feel where it pulls the hardest.  thats gonna give you a good idea even if the Pull is not great- you will know where the most power is made.  Most good sand car engine builders doing NA will make this between 2500 and 5500 because the X-over of TQ to HP happens on all engines at 5252 RPM and the theory is that once the HP starts top take over the car is already moving enough that TQ multiplication is not needed. TQ moves the mass afte rall and its the power you feel when accelerating.

Once you know the range - you use the Weddle calculator to set the shift points, and while the gear ratios are limited that we can buy  you can come pretty close to perfect, just remember to keep the RPM drops between gears as close to 500 RPM- 750RPM as you can and if the engine builder did not get stupid with too big cam  (not good for duning)  the car will perform excellently.

This is not my "concept" its how most car manufacturers do it and how just about every race does it.  How most duners used to do it is they had e a "buddy" with a similar car and engine combo that "worked" , and just copied their ratios .... That worked OK when most cars had the sme CBM Redline or Turnkey setup, but with so many different combos out there  - its not the best way... And don't forget, weight (car, axle, CV, and brake rotor size)  matter as much as tire size  and how tight the suspension is.

Just my 2 cents  ...
Click to expand...
Rpm drops at 500rpm? Is that a typo?

 
Jtmoney714 said:
Rpm drops at 500rpm? Is that a typo?
Click to expand...
General consensus is 500-750  RPM  drop is ideal 2nd-4th gear

at least for maximum performance  in a high perf vehicle

Some people stretch that to 1000 RPM, but it won't be fun to dune

Many people like to use  MPH drop vs RPM , but MPH is not usually too important in the dunes

This is good tool to use to test ratios

https://www.gtsparkplugs.com/GearCalc.html

 
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