More Teeth on the Speedo Gear Will Make Speedometer Read Lower, Right?

[harrisonm]

It has been a long time since I thought about this. I have had 205/70/14 tires on all four corners of my 69 Cuda with an 833 4 speed for a long time. The speedometer has been off by about 10 MPH for a long time. If the speedometer reads 65, I am really going about 55. I am finally going to do something about it. It seems to me that if I take the speedo gear out of the tranny and count the teeth, that my speedometer will read lower (more accurately) if I put in a new gear with more teeth. Kind of like a ring and pinion gear ratio question, right? With the ring gear being the speedo gear that I remove.

 

[67Dart273]

Yes. There are charts in the shop manuals, you can download them free at MyMopar. You will probably have to "work" to get the newer tire sizes, AKA figure yours for height or circumferance and then do the same for the old style sizes

 

[WV64Signet]

The speedo pinion should have a number stamped in it.

Options will be based upon tire diameter (height) and rear gear ratio

 

[72bluNblu]

From Brewers

Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists

 

[krazykuda]

More teeth will make the bite hurt more...

 

[69cudaownr]

Go to Transmission and Drivetrain Tech Forum and fully read the sticky in the top section Speedometer Gear Charts and Differences it addresses the chart and your tire size calculations. Don't use the Brewers Chart alone. Link below.
Speedometer Gear Charts - Clarification/Differences

 

[WV64Signet]

And something that I'm not clear on, and sorry for taking the discussion in a little bit of a tangent, The chart above and an online calculation tool that I have used both (for me) came up with a 41 tooth pinion... But if I go into the tech manuals and look at a comparable tire (14") the solution set was either a 19 or 21 tooth gear. Seemed like a pretty big jump to go from 17 tooth to 41 tooth when I'm only off about 10 MPH.

 

[George Jets]

Here is a 33 tooth speedo gear for 26" tire diameter and 3.23 rear gears.

 

[Professor Fate]

And something that I'm not clear on, and sorry for taking the discussion in a little bit of a tangent, The chart above and an online calculation tool that I have used both (for me) came up with a 41 tooth pinion... But if I go into the tech manuals and look at a comparable tire (14") the solution set was either a 19 or 21 tooth gear. Seemed like a pretty big jump to go from 17 tooth to 41 tooth when I'm only off about 10 MPH.

View attachment 1715996658

I think you're mixing apples and oranges- the Brewer's chart posted above is for '66 and newer transmissions, your FSM chart appears to be for '65 and earlier. They're two different animals.
Here's the full page from Brewer's:

 

[WV64Signet]

I think you're mixing apples and oranges- the Brewer's chart posted above is for '66 and newer transmissions, your FSM chart appears to be for '65 and earlier. They're two different animals.
Here's the full page from Brewer's:

Ahhhh... Gotcha. Thank you