Do gears mess up your odometer?

King Cobra 22 · May 7, 2004

Is it true that changing gears messes up your odometer because the car think's it's traveling at a different speed than it actually is thefore putting more miles on your odometer?I have heard this from alot of people and I'm wondering if it's true or not.

BlackVert · May 8, 2004

King Cobra 22 said:
Is it true that changing gears messes up your odometer because the car think's it's traveling at a different speed than it actually is thefore putting more miles on your odometer?I have heard this from alot of people and I'm wondering if it's true or not.

yes. i got 4.10s and my speedo is way off. also, my commute now registers farther than it used to, even though i go the same way.

the guy who sold the gears also sole me a speedo gear that he said would make the speedo right, but it isn't even close. when i'm going 85, the speedo says 100.

rio95 · May 8, 2004

yes, it is true.

King Cobra 22 · May 8, 2004

Black96VertGT said:
yes. i got 4.10s and my speedo is way off. also, my commute now registers farther than it used to, even though i go the same way.

the guy who sold the gears also sole me a speedo gear that he said would make the speedo right, but it isn't even close. when i'm going 85, the speedo says 100.

I've heard it's only off by 3-5%.At least that is what my mechanic said.

viperos · May 8, 2004

the same speedo gear is used for 3.55s and up... they are only exactly accurate for 3.55 gear ratio... I think that some places custom make a gear for 4.10s, but I know 3.73s are the same gear as 3.55s are... so, yes, to answer your question, it will mess up your odometer... but not too much... just get it as close as you can... that's all you can do...

King Cobra 22 · May 8, 2004

I always thought the odometer only counted when the tires go forward and I didn't think speed really mattered.

95GTvert[bv12] · May 8, 2004

you know my speedo is dead on with 3.73's i have tested it agianst new cars and it's dead on...so i am wonder how far off it was before?

GTPhreak · May 8, 2004

get a speedcal and your speedometer and odometer will be accurate. if you go over 3.55 there is no way to use a correct gear without also opening up the tranny and changing that gear

BlackVert · May 8, 2004

King Cobra 22 said:
I always thought the odometer only counted when the tires go forward and I didn't think speed really mattered.

speed doesn't matter. it assumes that every time the drive shaft rotates one time, the car has gone 26 / 3.27 = 7.95 inches. but with 4.10s, the car is actually going 26 / 4.10 = 6.34 inches. hence the odometer being off.

if you get wheels with a larger diameter in back, it will offset that some.

94TURBO5 O · May 8, 2004

You can purchase a plastic gear to go into the transmission to correct your speed. Mine was going 10mph faster until I put in the one for 3:73's.

BlackVert · May 8, 2004

94SC50 said:
You can purchase a plastic gear to go into the transmission to correct your speed. Mine was going 10mph faster until I put in the one for 3:73's.

the only down side to that is that you have to open up the tranny for it, which is not a very small task.

AznStanger3v · May 8, 2004

Black96VertGT said:
the only down side to that is that you have to open up the tranny for it, which is not a very small task.

yes it is. you dont have to open anything up. look on the drivers side toward the tail end of the tranny. there is a little transistor. pull ouf the harnass, use an 11 or 12mm open end wrench and take off teh ONE bolt and pull the transistor out. its a 7 minute job with nothing but the tools in your house.

AznStanger3v · May 8, 2004

my car is dead on with the 3.73s and 23 spline speedo gear. i tested it against those little radars that they put in neighborhoods. i was surprised, my old car was off by 3 mph. odd........

BlackVert · May 8, 2004

17yrOldStanger said:
yes it is. you dont have to open anything up. look on the drivers side toward the tail end of the tranny. there is a little transistor. pull ouf the harnass, use an 11 or 12mm open end wrench and take off teh ONE bolt and pull the transistor out. its a 7 minute job with nothing but the tools in your house.

cool!

JJ95GTID · May 8, 2004

Actually, the 23 tooth gear that Steeda and many others sell is for the 3.55 and 3.73 gear ratios and is an easy install. A 12mm socket and a pair for needle nose pliers will get the job done under a car that is raised up for access to the tranny. That 23 tooth gear is not dead on for either gear. Its ratio falls between the two gear ratios for a 'close enough' reading on the speedometer. The absolute best way to get the accurate speedometer reading is using the SpeedCal which corrects the speedo electronically . I use the 23 tooth gear and found it to be very close. At 95mph I am actually going 90mph showing a 5mph error. That error reduces as speed decreases. So, for every 95 miles I go I actually put 90 miles on it. No big deal I just do my oil changes sooner .

Imyourzero · May 8, 2004

What combination of drive & driven gears is needed to correct for 4.10's? I've got the 23-tooth white gear with (I think) the stock gear in the tranny and I'd much rather change those 2 gears than buy a $100 SpeedCal.

smokediver27 · May 8, 2004

Mines a weird one, its dead on regarding the speedo with my 3:73's and SpeedCal, but my odometer registers .9 miles for every mile traveled (checked this against the mile markers on the interstate, was a consistent finding)

jmuva44 · May 8, 2004

Yes

I just bought an Abbott ERA ratio adapter for mine. It has 3.73 gears in the back and a 23 tooth speedo gear but the speedometer is still off like 10 mph at 65. I

JJ95GTID · May 8, 2004

If you want to do the gear route in the tranny you will need to take off the tail housing off the T5 and replace your 8 tooth gear with a 6 tooth gear. Then match it with a 20 tooth gear for 4.10s'. This is according to the FRPP catalog.

Imyourzero · May 8, 2004

Thanks JJ95GTID!

Do gears mess up your odometer?

King Cobra 22

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