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Discussion Starter #1
I have noticed a few post mentioning the recalibration of your speedometer for larger tires. I did a search and came up with nothing. I know it is on here somewhere but I just can't find it. Can anyone help? i have an 89 SB 4" lift & 33's
 

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ate lug
88 + 96 broncos, 96 F250
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The thread youre probably looking for refers to the electronic speedos in the 92+ trucks ("whats a psom and how do i 'p' it", in the tech write-ups section).

Since yours is pre-92 it should still be using the mechanical speedometer, in which case you need to change the gear on the end of the speedometer cable, where it fits into the tailshaft of the tcase. I dont think there is a write-up because it is so easy to do that you will spend more time gathering the 2-3 tools required than you will actually changing the gear.

Basically, follow cable to where it enters tcase. Remove small bolt and pull bracket away. Cable will now pull out of tailshaft. then pry off the the little metal clip on the end of the plastic gear, and slide the gear off the end of the cable. All youll need is i think an 8mm wrench, and a small flathead.

In your case changing either tire size or axle ratio will affect the speedo. You can get new gears with a different # of teeth online but its easier to just get them from your local ford dealer. Difference in cost is minimal.

Read this thread by Ryan in the Tech Write-Ups section, and it will tell you how to figure out which gear you need.
 

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I am little confused by that thread. I have a auto transmission, but someone in the thread says it applies only to manual...or were they miss-informed? I went from the normal 245 tires, to 265, is that to little of a change to matter? I don't have a GPS to tell for sure.
 

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Discussion Starter #6
I am confused by that thread too. How do you know what your tire rev/miles are. Like I am running 33x12.5 so How do I know what I need?
 

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is that the same for an AOD?
Guys please, read the whole post:

Since yours is pre-92 it should still be using the mechanical speedometer, in which case you need to change the gear on the end of the speedometer cable, where it fits into the tailshaft of the tcase.
Doesn't matter what transmission you have. ALL transmissions (manual or auto) will spin the transfer-case gear the same. It's the speed that it spins at the determines how many feet your truck has traveled. When you change the tire's diameter, it's a longer distance that you travel at the same wheel speed as before. That's why your speedo says your going slower then your actual speed.
 

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ate lug
88 + 96 broncos, 96 F250
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The reason why there is mention of auto or manual, is because there is two different designs of the gear: one for automatics, and one for manuals (2wd only) & tcases. So since youre 4wd you would use the manual/tcase gear, not the auto gear, even if you have a C6, AOD, or E4OD. They look damn near identical but theyre not.
 

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Guys please, read the whole post:



Doesn't matter what transmission you have. ALL transmissions (manual or auto) will spin the transfer-case gear the same. It's the speed that it spins at the determines how many feet your truck has traveled. When you change the tire's diameter, it's a longer distance that you travel at the same wheel speed as before. That's why your speedo says your going slower then your actual speed.
That doesnt say "this is for both" it just says pre-92. But you answered the question. This will help me a lot, thanks.
 
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