Which speedo gear should i use?

J

jeepbro98

#1
#1
OK I HAVE A TJ JEEP WITH DANA 44 3.73 RATIO..31 1/2 TIRES....I KNOW HOW TO LOOK UP ON CHART..ON TIRE SIZE IT DOESN'T HAVE 1/2 INCREMENTS...LIKE 31 1/2 TIRES SHOULD I GO WITH 31'' TIRES ..OR STEP UP TO 32'' ON CHART......I'M SHOWING 4-5 MPG SLOWER THE ON THE DASH...CHECKED WITH GPS...SO IF I'M GOING 65 MPG ON DASH...GPS IS SAYING 70 MPG..I KNOW THIS IS NOT A BIG DIFFERENCE :smokin:BUT I'VE BEEN DOING A LOT OF MOD'S TO SAVE GAS..SO BY THE SPEEDO GEARS NOT MATCHING TIRES SIZE SHOWS DIFFERRENCE:confused:....THNX JEEPHEADS ....HAPPY NEW YEAR (JEEPBRO)
 
97TJGUZZY

97TJGUZZY

SUPPORTER
#2
#2
your speedo is showing 4-5mph slower at what speed? speedometers are exponential, so is that 4-5mph at 15mph or at 80mph? Check and see what speedo gear you have now by pulling it out of the tcase and checking the number.
 
M

meaders

#3
#3
97TJGUZZY said:
your speedo is showing 4-5mph slower at what speed? speedometers are exponential, so is that 4-5mph at 15mph or at 80mph? Check and see what speedo gear you have now by pulling it out of the tcase and checking the number.
Click to expand...
he just said "if i'm going 65 on dash...gps is saying 70"
 
WolfGT

WolfGT

LIFETIME
SUPPORTER
#9
#9
We don't understand because you confused us with, um ... this: SO BY THE SPEEDO GEARS NOT MATCHING TIRES SIZE SHOWS DIFFERRENCE.

What does that mean? And what do you want to really know? You aren't going to get right on the money with the speedo. I wouldn't even sweat 4-5 mph.
 
Shilohsho

Shilohsho

#10
#10
Looks like your stock speedo gear is probably a 35t. 65/70=.92
Multiply .92 x 35= 32.5. Get the 33t and you'll be close enough. The chart shows 32&33 for 31&32" tires. You'll be all over it then.
 
M

meaders

#11
#11
Its not rocket science people, just because he has some spelling and typing errors its not that hard to figure out what he's talking about. He wants his speedometer to be more accurate so he can calculate his fuel mileage after doing mods to improve it.
 
WolfGT

WolfGT

LIFETIME
SUPPORTER
#12
#12
Oh. I get it. Because not only will the mph be off but the distance traveled will be off too. Correct?
Sent from my Lumia 920 using Board Express Pro
 
Shilohsho

Shilohsho

#13
#13
Yes Greg, both mph and mileage will be off by the percentage. In this case his is reading 8% slow, therefore it won't always be 5mph off. It will be 8% slower at whatever speed the guage shows he is traveling.
My work truck is 13% off and has been for years. It shows that I've put 120k miles but its more like 120 x 1.13.
 
J

jeepbro98

#14
#14
Shilohsho said:
Looks like your stock speedo gear is probably a 35t. 65/70=.92
Multiply .92 x 35= 32.5. Get the 33t and you'll be close enough. The chart shows 32&33 for 31&32" tires. You'll be all over it then.
Click to expand...
Thanks Shilohsho understand completely,but .92x35=32.2 so should i still get 33 teeth speedo gear? 0r 32 teeth? :smile:Thank you Sir
 
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