Speedo gear
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From: Kent WA
Speedo gear
Anybody got the right speedo gear to fit a 1345 transfer case paired up with 4.10 axle gears laying around someplace?
My truck came with 3.55 gears and has had the axles swapped to 4.10 gears. The speedo is reading nearly 15% fast and I need to fix it...
My truck came with 3.55 gears and has had the axles swapped to 4.10 gears. The speedo is reading nearly 15% fast and I need to fix it...
i ain't rite
Joined: Mar 2005
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From: Marlboro Mental Hospital.
if i remember correctly, you want to drop 1 tooth on the speedo gear for every 2.5 miles over the speed you are doing.
so if you are going 5 mph faster than the speedo says, you will want to drop 2 teeth on the gear.
but double check that, it may be remove teeth. it has been over 15 years since i messed with speedo gears
so if you are going 5 mph faster than the speedo says, you will want to drop 2 teeth on the gear.
but double check that, it may be remove teeth. it has been over 15 years since i messed with speedo gears
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From: Bald Knob AR
I just went thru this with my 90 model a couple months ago. One tooth equals a 7mph change. If your speedo is reading 7 mph fast, go down one tooth, if it reads slow go up one tooth. You can get the gears at any ford dealer. They are about 5 bucks apiece.
i ain't rite
Joined: Mar 2005
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From: Marlboro Mental Hospital.
it stinks getting old and forgetting simply things like that.
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From: Kent WA
Not trying to be a jerk, but there are a couple things I have to disagree with in your statements...
7mph change at what speed? The amount of change isn't a fixed number - it is a percentage. If it is 7mph off at 30mph, then it will be 14mph off at 60mph, and 21 mph off at 90mph - assuming you can get it to go that fast 
Logically, I believe you stated this backwards. Think about it. A smaller gear (one fewer teeth) will actually spin faster (not slower) - making the speedo read faster at the same speed. Conversely a larger gear on the end of the speedo cable will turn the cable slower - making the speedo read slower at the same speed...
Logically, I believe you stated this backwards. Think about it. A smaller gear (one fewer teeth) will actually spin faster (not slower) - making the speedo read faster at the same speed. Conversely a larger gear on the end of the speedo cable will turn the cable slower - making the speedo read slower at the same speed...
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From: Bald Knob AR
Not trying to be a jerk, but there are a couple things I have to disagree with in your statements...
7mph change at what speed? The amount of change isn't a fixed number - it is a percentage. If it is 7mph off at 30mph, then it will be 14mph off at 60mph, and 21 mph off at 90mph - assuming you can get it to go that fast
Mine was reading 74mph at a GPS indicated 60mph. It had a 19 tooth gear on it and I changed it to a 21. Now it reads right. That is changing the gear on the end of the speedo cable. If you need to make corrections that are not at 7mph increments then you will need to change the gear inside the tcase too. You didn't indicate a speed either, you just said it was 15% off. I've never seen a set of gears that corrected itself for different speeds traveled. .
Logically, I believe you stated this backwards. Think about it. A smaller gear (one fewer teeth) will actually spin faster (not slower) - making the speedo read faster at the same speed. Conversely a larger gear on the end of the speedo cable will turn the cable slower - making the speedo read slower at the same speed...
7mph change at what speed? The amount of change isn't a fixed number - it is a percentage. If it is 7mph off at 30mph, then it will be 14mph off at 60mph, and 21 mph off at 90mph - assuming you can get it to go that fast
Mine was reading 74mph at a GPS indicated 60mph. It had a 19 tooth gear on it and I changed it to a 21. Now it reads right. That is changing the gear on the end of the speedo cable. If you need to make corrections that are not at 7mph increments then you will need to change the gear inside the tcase too. You didn't indicate a speed either, you just said it was 15% off. I've never seen a set of gears that corrected itself for different speeds traveled. .
Logically, I believe you stated this backwards. Think about it. A smaller gear (one fewer teeth) will actually spin faster (not slower) - making the speedo read faster at the same speed. Conversely a larger gear on the end of the speedo cable will turn the cable slower - making the speedo read slower at the same speed...
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From: Bald Knob AR
BTW. Just to make it more confusing. When you go to the dealer to ask for the new gear. You will need to know what color gears you have. They have some gears that have the same number of teeth but are different colors. If you don't get the right color it still won't read right. I havent figured this one out yet but I found that out the hard way.
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Lead Driver
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From: So. Jersey
Another thing you need to consider is tire size. Anyways this link should help you choose or at least they can answer your questions.
Speedometer Gear, Speedometer Gears, Ford
#F8T. Fits some 1980 to 1993 F150 / F350 and some 1993 to 1994 Explorer standard 2WD transmissions. Also fits some Ford Borg Warner 1345 transfer cases. Has 8 teeth. (OUT OF STOCK) Cost $49.00
Speedometer Gear, Speedometer Gears, Ford
#F8T. Fits some 1980 to 1993 F150 / F350 and some 1993 to 1994 Explorer standard 2WD transmissions. Also fits some Ford Borg Warner 1345 transfer cases. Has 8 teeth. (OUT OF STOCK) Cost $49.00
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i ain't rite
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From: Marlboro Mental Hospital.
hey cheeper, if you know what tooth gear you need, let me know. i will look in the tool box and see what i have out there. if they will work for you, you can have them .i will never need them again, as i do not plan on changing tire size or gears in my trucks.
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From: Kent WA
Mine was reading 74mph at a GPS indicated 60mph. It had a 19 tooth gear on it and I changed it to a 21. Now it reads right. That is changing the gear on the end of the speedo cable. If you need to make corrections that are not at 7mph increments then you will need to change the gear inside the tcase too.
BUT your speedo was reading fast and you put in a gear with MORE teeth to correct it - just like I said. That is still the opposite of what you originally said - which was "If your speedo is reading 7 mph fast, go down one tooth..."
The flaw in your logic here is simple. What you are saying would be true if the two different gears were different diameters. They are not. They are the same diameter just one has more teeth than the other. A 17 tooth gear is the same diameter as a 19 or 21 tooth gear. The more teeth the tcase gear has to move, the slower it will turn.
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From: Kent WA
Cool deal man. I'm eyeball deep in another project right now, but soon as I get a chance (maybe next weekend) I'll pull it out and take a look. Thanks.
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