Speedometer question

[Redneck_4x4]

I got a 88 K-5. I am running 4.56 gears & 38's. The speedometer is reading about 20 MPH faster than what I am actually going. Example; I going about 65, speedometer says 85. My speedometer is cable driven, Does anyone know what I can do or where I can get something to fix it. Thanks for any help.

 

[rescue6]

replace the spedo drive gear there are plenty of calculators out there to help you choose the right one just google it here is on for you http://www.sccoa.com/faq/speedgr.html

 

[Redneck_4x4]

So I can just pull the piece where the cable screws in and change the gear. Another question; Which is the drive gear and which is the driven gear, I would guess that the one on the output shaft would be the drive gear. Also, what size drive gear is normally in a 208, I believe that the stock rear end gears were something like 2.73. Thanks

 

[rescue6]

you just change the gear that is atatched to the end of the cable it should just clip on. you dont have to dissasymble anything just remove the retaining bolt and pull the cable and the replace the spedo gear.
Natches huh, I used to live just south of there in Woodville

 

[Redneck_4x4]

Yeah, Natchez. I know a couple of people from Woodville. Do you know what drive gear is in the case or how to find out?

 

[Mike D]

Here is a rule of thumb, get a buddy and go on an interstate ( they have mile markers ), at a true 60 mph you will pass a mile marker every 60 seconds ( your buddy's job is towatch the watch second hand and the mile markers, your job is to maintain a constant speed and watch the road ). Now you state your speedo reads 20mph too fast. If this is correct you have to maintain your speedo at 80mph in order to pass a mile marker every 60 seconds ( 60mph ). Once you are satisfied with how much error your speedo is actually off, pull the cable off your trans case and remove the gear the cable is connected to. Now count the teeth on the little gear. For every tooth you add you will reduce the speedo reading by 3mph. Therefore if your little gear has 11 teeth and you replace it with one that has 18 teeth your speedo will now read 60mph. It is possible that GM only makes a 17 or 19 tooth gear. And the new gear may not work well with the the drive gear on the transfer case output shaft, but for $3 - 5.00 it is worth the gamble.

 

[AJMBLAZER]

http://coloradok5.com/forums/showthread.php?t=193019&highlight=gear+speedo

 

[Big Blzn]

I got a 88 K-5. I am running 4.56 gears & 38's. The speedometer is reading about 20 MPH faster than what I am actually going. Example; I going about 65, speedometer says 85. My speedometer is cable driven, Does anyone know what I can do or where I can get something to fix it. Thanks for any help.

Great thread and answers some of my questions too. However, Mine is just the opposite. I have 3.08 gears and run 35" tires. My speedo says I'm running 50mph but my GPS says 71mph. Even though we have different gear and tire sizes why would our variences be in the opposite end of the spectrum? Still seems as though Rednecks speedo would be running slower than his actual speed?.?.?

 

[AJMBLAZER]

Your variance is simply because the only thing changed was the tires. Speedos simply measure revolutions of the driveshaft at the output. Since your tires are taller and have more diameter you are covering more ground with each revolution. Hence your indicated speed is slower than your actual speed.

His truck has been regeared AND had taller tires put on. This changes two of the variables in the speedo equation and explains the slower actual speed when compared to the speedo.

 

[Redneck_4x4]

Thanks, I think I'm going to pull the driven gear and see what count it is. Then I will try and figure what will get me close. I don't care if it is off up to 2 or 3 mph, I just don't like going down the road at 80, just to keep up with traffic.