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My head hurts math.

skipnrocks

Well-Known Member
Joined
Oct 1, 2011
Messages
1,355
Location
Billings Montana
I'm trying to correct the speedometer readings on my kids transaxle buggy. The problem that I have is if I put in the Total drive gearrange which is 8.24. 538 in the axles and 286 is in the transaxle. Then it messes my stuff up even more. I believe this is because the output speed sensor is on the transaxle so the gear ratio is only 2.86 but it thinks it's 8.24.


my theory is that I have to correct this gear ratio in the axle through adjusting the tire size. My mind says that I should make the tire diameter in the computer 1/5 what it says or 5 times what it says but either way I can't get it to come out right help me guys how my miss thinking this
 
The computer wants to see my speed to determine trans shifting. I can keep shift points oem and let it think it's driving a car on 27 in tires and it will shift correct. But if I can figure the math I should be able to get a functional speed reading for the digital dash also.
 
Maybe I have it figured out? Keeping the gear ratio the same to compensate for 39 in tires and 5.38 gears in the axle I need to leave the gear ratio in the computer at 2.86 because it's accurate and change the tire size to13.5 in. My math says that should put it close.

Or am I crazy
 
Nick's math is correct to get the right ratio, but I believe your total gear ratio is wrong.

It should be 2.86 x 5.38 for 15.39 vs 2.86 + 5.38.

So that would make the tire size need to be 7.25".

If your current math works for the ecm, then disregard.

Sent from my SM-G955U using Tapatalk
 
Re: Re: My head hurts math.

paradisepwoffrd said:
Nick's math is correct to get the right ratio, but I believe your total gear ratio is wrong.

It should be 2.86 x 5.38 for 15.39 vs 2.86 + 5.38.

So that would make the tire size need to be 7.25".

If your current math works for the ecm, then disregard.

Sent from my SM-G955U using Tapatalk

Yeah that is correct

Should make it shift like stock.


You can cheat the tire size input to make it shift sooner or later. Hillbilly shift kit. Not exact science
 
So what I ended up doing was getting the shift points good for real world driving and then used the app for the digital dashboard to manipulate the speedometer and now I have good shifting and accurate speedometer. Pretty cool.
 

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