speedometer funcion

[jlangholzj]

here's the deal:

When my speedo says I'm going 50-its actually 60 (i had the sherif clock me)

my question is, is the difference lesser at lower speeds and greater at higher?? in other words, does it mean that I'm 20 off when it says I'm close to 90??

-John

 

[Rusty67]

Yes, is gets less acurate as your speed increases. The reason for this is that the speedo works based on a gear ratio so as it is moving faster, what was first a marginal difference starts to become rather significant. You need to get the correct speedo gear for your rearend/wheel/tires. They are EASY to change out.

 

[65ShelbyClone]

Speedometer inaccuracy is usually specified as a percentage. Yours is about 16-17% low. That means it will read 75mph when your actual speed is 90mph, a difference of 15mph whereas the difference was only 10mph at the lower speed(60).

 

[EP429]

You need to get the correct speedo gear for your rearend/wheel/tires. They are EASY to change out.

My speedo cable didn't want to come out of the tranny once. If at first it doesnt play nice, don't force it, turn the engine and try again. Might save you the expense of a new cable
I wish I hadn't learned that one first-hand, shipping parts ruins a "quick" fix

 

[suki243]

Did you get a ticket? My speedometer was off; it told me i was going 85 and trucks on the freeway were passing me ...,eventually my speedo cable broke cause i forgot to screw it in all the way, it came out a bit and the back of the speedometer ate up the end of the cable. Now, I end up going with the flow of traffic but I'm always afraid of a ticket. Just wondering if you could use that as an excuse.

 

[65ShelbyClone]

Don't count on it. Legally it is your responsibility to maintain the car and that includes ensuring your speedometer works.

With that said, I drove a '65 notchback I used to have for probably two years looking at only the tach after the cable broke. However, I was actually able to judge my speed that way with some accuracy.

 

[dodgestang]

Don't count on it. Legally it is your responsibility to maintain the car and that includes ensuring your speedometer works.

With that said, I drove a '65 notchback I used to have for probably two years looking at only the tach after the cable broke. However, I was actually able to judge my speed that way with some accuracy.

Only 2 yrs I'm going on 6 with mine

Getting the speedo gear is on the list....its just at the bottom.

 

[jlangholzj]

Did you get a ticket? My speedometer was off; it told me i was going 85 and trucks on the freeway were passing me ...,eventually my speedo cable broke cause i forgot to screw it in all the way, it came out a bit and the back of the speedometer ate up the end of the cable. Now, I end up going with the flow of traffic but I'm always afraid of a ticket. Just wondering if you could use that as an excuse.

NO, thankfully, but i know the local sherif really well, and we just went out on a tar outside of town and clicked it. besides, he had been wanting to see my car


I'll have to get another speedo gear, but since i know where I'm at, I don't forsee it to be that big of an issue.

currently I'm running 225/R1470 on the rear tires and its a C-4 . The rear ratio is 3.00 , open differential.

I'll graze around on the net to see what i can find, but if anyones got a link, feel free to post it

 

[jlangholzj]

Note:

I esimated my tire height in inches at 26.4 and according to one site i found, I would need a speedo gear with 18 teeth. does this sound about right??