I got pulled over last night for going 73 in a 55 luckily I got off with a warning, but here is the problem my speedo said I was going about 50-55 so my speedo is way off, how can I go about getting it re adjusted my self with out going to the dealer or getting a programmer

also how much does the dealer charge to fix it

also my tire size is 315/75r16

 

Normally you need to go through all the tire diameter of original equip, vs. what's on there to get the immediate speedo discrepancy out.

Not sure if you're in the mechanical era or electronic one, normally it's speedo gear changes for the old school style.

Or if you're electronic, I think you have to get a programmer.

Then there's the issue of the odometer...

 

get a GPS for less than 200 bucks and it clocks accurate mileage and accurate speed regardless of vehicle or wheel size!

 

THe 97-98's are recallibrated with a plastic gear on the tranny.

 

after reading quite a bit I learned that I do need a plastic gear but I have 2 problems

1st being what gear do I need
2nd when i do the math to see what I need it says I need a 13 toothed gear but that does not sound right or is it

 

You can get very close by using a sweep second hand on your watch and the mile markers on the highway.
If your speedo is saying 60 mph and it takes one minute, your speedo is correct. Any variation can be solved for by dividing the number of seconds into 60 to get a ratio to select another vss driven gear.
So, if your speedo is 10% slow, add 10% more gear....12(teeth) x 110% = 13.2, so a 13 tooth gear will be close.

 

Ok so I did the math again and also based on what speed I was going when I was pulled over which was 60 and the state trooper gave me a warning for going 73 which would mean that my speedometer is slow by 21 percent so now all I need to do is count the teeth on my speed sensor and buy the one it needs, which since i have a 17 tooth(I think) I need to get a 19 tooth...does the dealer sell these?

 

so i went out this morning and found out that I have a red gear which is a 21 tooth, and if my math is correct I need about a 23 tooth gear to get it corrected does the dealer carry this and if not how can I go about correcting a roughly 21% error in my speed

 

I think you are doing something wrong on my 97 when i put bigger tires on i had to go down in teeth size....bigger tires makes the spedometer slower so your need to speed up the spedometer by using a smaller gear..

 

Oh I see then so is there some way to definitely figure out how many teeth I need

edit: I used this formula and got that I need a 17 tooth gear and drop it from a 21 tooth

New Teeth = (Current Teeth x Speedo Reading)/Actual Speed.

does this sound correct

 

that sounds better I cant remember what i have with 285/70/17 but i will check tonite and get back to you

 

Well I went to the dealer today and bought the 17 tooth gear and put it on and it seems to be a little more accurate(I time my self to get to 60 before which was at 50 mph and it took 16 seconds, slow I know, and then after I timed it to 60 at the 60 mark and it was 16 seconds to get there) so it seems to be good.

 

You need to time a measured mile or use a GPS to see how close it is. You can't just guess like that.

Go out on the Interstate and hold it steady at any speed, use your cruise control if you have one. Time it for exactly one mile. Divide the number of seconds into 3600 to get actual speed.