Speedmeter off by 10 MPH Need Help

[jg5899]

For some odd reason my Speedometer is 10 miles faster than the car is actually going and in the 80+ MPH it goes off by 30 MPH.
I need help, does anyone have any idea why this would happen ??

 

[IJ.]

Has it had the Diff ratio swapped?

 

[jg5899]

Has it had the Diff ratio swapped?

Not that i know of, how would i be able to find this out?

 

[IJ.]

Jack it up turn the Driveshaft and count the rotations of the wheels then divide one by the other.

Being an NA it "should" have a 4.30:1 gear set in it.

 

[Ma70.Ent]

The only experience I've got with the speedometer being off that much is when a 3.73 diff is swapped in place of a 4.30 ratio.

 

[TomFraser]

mine does the same thing... it's a turbo auto and the LSD has never been changed, so it can be that off becuause of other things, I have yet to look into it as I don't really care enough

I plan to start with replacing the speedo cable, and inspecting behind the dash (odo, etc.) as the trip odo sometimes works, sometimes doesn't

 

[jg5899]

Jack it up turn the Driveshaft and count the rotations of the wheels then divide one by the other.

Being an NA it "should" have a 4.30:1 gear set in it.

I checked and it is 4.30:1
Does that mean theres an issue with the tranny?

 

[IJ.]

Only thing I can think of is the incorrect driven gear on the end of the cable.

 

[jg5899]

mine does the same thing... it's a turbo auto and the LSD has never been changed, so it can be that off becuause of other things, I have yet to look into it as I don't really care enough

I plan to start with replacing the speedo cable, and inspecting behind the dash (odo, etc.) as the trip odo sometimes works, sometimes doesn't

My trip odo works all the time.
My concern is that the odometer is not accurate anymore, and also that i have to keep a special mental note to remember thats not really how fast im going

 

[jg5899]

Only thing I can think of is the incorrect driven gear on the end of the cable.

How would i be able to check? And if that is the problem how much would a new cable end run me?

 

[IJ.]

The gear itself is available so if your speedo isn't stuttering it should only be a few $ to replace the gear.

I don't have one here to check how many teeth are on it sorry, I'm sure someone should jump in though.

10Mph is a BIG error and this is why I think it's the wrong gear, remember tire size/diameter has an effect as well.

 

[armyastro]

get a dakotadigital.com speedo calibrator

 

[armyastro]

http://www.dakotadigital.com/index....tegory_id=287/home_id=59/mode=prod/prd126.htm

 

[IJ.]

http://www.dakotadigital.com/index....tegory_id=287/home_id=59/mode=prod/prd126.htm

Care to explain how this will work with a mechanical Speedo?

 

[jg5899]

The gear itself is available so if your speedo isn't stuttering it should only be a few $ to replace the gear.

I don't have one here to check how many teeth are on it sorry, I'm sure someone should jump in though.

10Mph is a BIG error and this is why I think it's the wrong gear, remember tire size/diameter has an effect as well.

Not sure what stock tire size is supposed to be but i have 225/45 on some 17's

 

[TomFraser]

My trip odo works all the time.
My concern is that the odometer is not accurate anymore, and also that i have to keep a special mental note to remember thats not really how fast im going

your odo is wrong if the speedo is wrong, and the mental note works after about 3 days, you just remember. Confirm 4 or 5 points on a GPS with the speedo (when my speedo says 60 I am at 45)

 

[IJ.]

There's only .1" difference in diameter between stock and your tires so that pretty well rules that out.

 

[jg5899]

Could it be possible that whoever had it before me swapped out the tranny?

 

[IJ.]

Maybe but it might have been as simple as a cable from a junkyard with the different gear.

 

[jg5899]

Maybe but it might have been as simple as a cable from a junkyard with the different gear.

I think ill just replace the gear then.
Know where to get one? Would the dealer be my bet bet?