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...

 

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

 

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.

 

thanks for clearifying that.

it stinks getting old and forgetting simply things like that.

 

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...

 

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.

 

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.

 

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

 

decent prices on the gears, but their calcultor is useless. it only goes up to a 28 inch tire.

 

I bought that same gear at the Ford dealer minus the metal sleeve which you don't need. It was only about 7 bucks.

 

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.

 

OK, so then yours was reading 7mph fast at 30mph. That's 23% fast - which is even worse than mine. You must have changed tire size on yours as well.

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..."

Yes, when expressed as a percentage you don't need to specify the speed. It's 15% fast at all speeds (at 30mph, it reads 34-35mph, at 60mph it reads 69mph, at 90mph it reads 103-104mph, etc)

Sorry, that almost seemed to make sense for a second there, but as explained earlier, it leads to an answer that is opposite of what you said you did - which is put in a gear with MORE teeth to bring the indicated speed on your speedo DOWN to match the speed on your GPS...

 

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.

 

i just dug them out of the box. i have 1=17, 1=18, and 1=19.
let me know.