Speeod gear replacement cause of 33" tires, what tooth count needed?

[reamer]

I currently have a "white gear", 19 tooth, but changed from 28" tires to 33" tires, Speedo off now.
65HPH (actual by Waze satellite) is reading 73 MPH on speedo. do I need to go up in tooth count?

 

[Broncobowsher]

Yes, up the tooth count on the cable side. That slows the cable down.
19 tooth and still reads slower than actual, you must have some steep gears in it.

 

[Steve83]

Read this page:

(click this text)

 

[reamer]

just 3:50's with a C-4

 

[reamer]

Well that was not correct. took out the 18 tooth (40mph on speedo dial = 44 actual) and installed a 19 tooth. now 40mph on dial reads 46-47......

 

[Viperwolf1]

Something isn't correct. Should be no way to get speedo close to correct (within 10 percent) with 3.50 gears and 33" tires. A 19 tooth driven gear should be closer to 20 percent off. I'm going to say something wrong with the drive gear in the tcase or cable or speedo itself.

 

[reamer]

Should be a 16 or 17 tooth

 

[FordBronc]

Maybe this will help?

 

[B.ranch]

Seems like when I changed my Speedo gear, they were color coded and burgundy was for 33s but I'm prob remembering wrong it's been a long time ago

 

[Steve83]

The color of the driven gear depends on the drive gear, the rear axle ratio, AND the tire size. So no, burgundy is not always for 33s.

 

[tasker]

GENERALLY speaking one tooth is 5 MPH

 

[Broncobowsher]

GENERALLY speaking one tooth is 5 MPH

At about 60MPH. Important detail. As being off by 5MPH at only 30 would be twice the error.

More correct, the error is a percentage error. If the tire size or gear ratio changes 10%, the speedometer error is also 10%. Not a fixed offset error.

 

[reamer]

The winner is... 16 tooth! Dead nuts on, 40 =40, 60=60!