speedo gear ?
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Freshman User
Joined: Oct 2005
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speedo gear ?
Hi all, I have noticed that my 85 f250 4x4 Regular cab speedometer is showing between 5 to 8 mph faster than my actual speed. Going 30 on speedometer is actually 20-25+ or -. What speedo gear do I actually need. I have 265-75-16 tires and the manual 4 speed. The door shows an axel code of 39, trans code of P, and spring code 9GK. Front Gawr of 3850 and rear Gawr 5922. A buddy of mine keeps telling me that he thinks that the rear axel has been changed because my brake drums come off without taking apart the ?axle? Could he be correct? The guy I bought it from was a farmer and the original owner, I can't get ahold of him to find out if it had been changed. How hard is it to change the speedo gear? Any info would be great. Thanks, Preston
Methanoholic
Joined: Mar 2009
Posts: 6,442
Likes: 8
From: Maine (NorCal Native)
Because there are several different drive gears it is better to find out what driven gear is currently used, that gives a good reference to what the drive gear is, in tooth count and style.
The tooth layout can be either way: \\\ or ///
NumberDummy has posted great info several times on this with all the numbers and everything else recently.
Then you can use one of several calculators to find the correct driven gear to correct the speedometer.
Personally I like the one at TCIAuto.com.
There is one at the top of the FTE pages under:
Or you can just go one tooth larger and that should be about right for your situation. One tooth is about 10%.
-Enjoy
fh : )_~
The tooth layout can be either way: \\\ or ///
NumberDummy has posted great info several times on this with all the numbers and everything else recently.
Then you can use one of several calculators to find the correct driven gear to correct the speedometer.
Personally I like the one at TCIAuto.com.
There is one at the top of the FTE pages under:
- Articles/Specs
- Automotive Calculators
Or you can just go one tooth larger and that should be about right for your situation. One tooth is about 10%.
-Enjoy
fh : )_~
Methanoholic
Joined: Mar 2009
Posts: 6,442
Likes: 8
From: Maine (NorCal Native)
Dirt.
Don't remove the cable from the adapter, don't need to. (or whatever it's technically called)
They are color coded to a point.
It's easier just to take it (the gear) to your local Ford dealer, some carry a good selection of them in stock, some don't.
I pulled my gear, put it back together without the gear (or c-clip), drove to the dealer and installed the new one in the dealers parking lot.
Shouldn't take more than a couple minutes to change.
-Enjoy
fh : )_~
Don't remove the cable from the adapter, don't need to. (or whatever it's technically called)
- One bolt.
- Pull the cable and gear out. (should slide right out)
- Remove the C-Clip. (Just pulls off/out)
- Remove the gear.
They are color coded to a point.
It's easier just to take it (the gear) to your local Ford dealer, some carry a good selection of them in stock, some don't.
I pulled my gear, put it back together without the gear (or c-clip), drove to the dealer and installed the new one in the dealers parking lot.
Shouldn't take more than a couple minutes to change.
-Enjoy
fh : )_~
Methanoholic
Joined: Mar 2009
Posts: 6,442
Likes: 8
From: Maine (NorCal Native)
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Freshman User
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Thanks for the input, I am going to try to take it out this weekend, Just had a brake cylinder go out and have to hit that one first. Also found that my original muffler is rusting out. Will I have any problems if I straight pipe it?
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