speedo gear problem

[nooberiffic]

My 1990 Ranger (4wd, supercab 5 speed, 3.73 gears) had 235/75R15 tires on it when i got it. Stock im pretty sure it had 225's. Anyway, the speedo was off, so I changed the white (17 tooth?) gear to the wine colored 16 gear one. That seemed to fix it, as using the speed things cops set up I was on at 45 (giver or take a mph).
I recently put on 31's, but cannot find a smaller speedo gear. Anyone have any answers?

 

[nooberiffic]

bump

 

[nooberiffic]

anyone, any idea's?

 

[pillen140]

get someone else to verify your speed, and remember how much its off. thats all i do, the speedo is 18% off with my 33's compared to stock 215/75r15s

 

[cowboykilroy]

If you have or can borrow a GPS set it to the screen that displays MPH.Then make notes for various speeds and the differences.

 

[Earl43P]

http://www.therangerstation.com/tech_library/Speedogear.html

http://www.therangerstation.com/tech_library/Speedometer_Change_From_Tires.html

 

[feellnfroggy]

old tire size over new tire size times x over old speed. But Ill go ahead and do the math for you , at 55mph with 31's your actually doing 58.8 You can verify this with the same speed machine you used before. My stock speedo gear and 3.27 stock gearing with 235's was 2mph slower than actual speed (from the factory ford does this with all thier cars) when I added only 31's my speedo was dead on, I have 33's and 3.55's with the factory speedo and again Im pretty much deadon.

 

[AllanD]

My 1990 Ranger (4wd, supercab 5 speed, 3.73 gears) had 235/75R15 tires on it when i got it. Stock im pretty sure it had 225's. Anyway, the speedo was off, so I changed the white (17 tooth?) gear to the wine colored 16 gear one. That seemed to fix it, as using the speed things cops set up I was on at 45 (giver or take a mph).
I recently put on 31's, but cannot find a smaller speedo gear. Anyone have any answers?

actually stock rubber on that would have been 215/75-15



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[nooberiffic]

Thanks Allen. Does anyone know of any other make of vehicle that used the same driven gear/drive gear speedo setup at the early '90 fords? Perhaps they made gear with less teeth...
My rear main is going to be replaced under warranty, so I suppose I could get the worm gear on the output shaft replaced (I think there are two sizes), then I could find the correct speedo gear size. Anyone know the stock worm gear size, and the alternate?