Adjusting the Speedometer

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jdconnel
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Adjusting the Speedometer

Post by jdconnel »

It would seem that my speedo doesn't read right. 60 = 45 from the best I can tell.
If this just becasue the cable has stretched, and I need a replacement, or is there a way to adjust this?
Also, I notices on DC that there are two lengths of cables. Anyone know what should be in my '67 F250?
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re: Adjusting the Speedometer

Post by 69rangerman »

I have the same prob. My indicated is 5 mph higher than actual. Checked it via cel phone with my wife.
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Post by rjewkes »

IIRC it has something to do with your tire size and your rearend.
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re: Adjusting the Speedometer

Post by Jake11 »

They make different gears
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re: Adjusting the Speedometer

Post by xxxtina63 »

Did you replace the trans?
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re: Adjusting the Speedometer

Post by FORDification »

The cable isn't the cause. It's the result of a mismatch between the rearend gears and the speedometer drive gears in the transmission. A previous owner has either put different rearend gears in and/or replaced the transmission with one from a vehicle with different rearend gears. Dramatically changing tire size will also have some effect, but not to the degree that you're showing.

To correct the speedometer, use the information on the following page:

http://www.tciauto.com/Products/TechInf ... _gears.asp
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Post by jdconnel »

I will try and pull some info off the transmission.
I didn't think it was changed over, but the numbers will tell the tale.
Wheres a good location to look for a stamping or ID on the trans?
Also, what is the factory tire size for a 67 F250? I think it has to original 16.5" rims on it now.
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re: Adjusting the Speedometer

Post by jdconnel »

OK, so I've ID's the rear end as a Dyna 60 (4.10 G.R.) as per the tag on it, just like the door tag id states too. :thup: Yeah original!

So this obviously means I have the wrong cable installed? I wouldn't be surprised if the guy replaced it with the wrong one just to get things moving again. Or am I missing something else? Just want to make sure before I go buy the wrong cable again….
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Post by rjewkes »

the cable is fine i'm placing my mony on the gear in the trans or more acurately the one on the end of the cable as it goes into the trans.

could have too many or too little(amount)of teeth.
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Post by jdconnel »

Wonder if the old one broke, and the prvius owner just tossed something in.... That's what I'm leaning towards here.
How many teeth should it have, and whats the best wat to remove such said little gear? I'm prob due to change the oil in the diff while I'm laying down there too.
Recommended replacement oil?
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Post by rjewkes »

i don't know on the number of teeth nbut that atleast two different amounts exist.

IIRC its either 80 w gear lube or 80/90 weight.
"It is better to keep your mouth shut and appear stupid than to open it and remove all doubt." - Mark Twain
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Post by 71PA_Highboy »

jdconnel wrote:Wonder if the old one broke, and the prvius owner just tossed something in.... That's what I'm leaning towards here.
How many teeth should it have, and whats the best wat to remove such said little gear? I'm prob due to change the oil in the diff while I'm laying down there too.
Recommended replacement oil?

Teeth don't break off... and if they did you would see it as 'jumpy'.

Pull the speedo cable out of the tranny... count the teeth on the gear. Go to your Ford dealer but a new gear with 3 more teeth than you have on your current gear.

hth,

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re: Adjusting the Speedometer

Post by A_G »

would swapping out a completly new rear end cuase the speedo to no work at all?

My dad blew a ring gear through the side of the pumpkin back in the day, ANd now it has a 70s dana 60
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re: Adjusting the Speedometer

Post by 71PA_Highboy »

The rear end has nothing to do with the speedo's operation, only it's accuracy.

Pull the cable and see what gear is on there, if there is a gear, spin it with a drill and see what happens... if no gear, go buy one....

No movement of the needle = pull the cable and watch the speedo end... no movement of the cable now means bad cable... movement of the cable means bad speedo.

hth,

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