Speedometer Gear question

[bob32268]

I switched my 3:55 rear center section diff of my 69 Charger to a 3:23 Sure-Grip center section (8.75 489 case). Now, my speedometer is "off". I checked Classic Ind. catalog and they list the replacement gears by tooth count and color but not which rear end gear ratio that they are for. What is the correct tooth count and color for the 3:23 Sure-Grip? also, the 3:55 Sure-Grip ? Thanks in advance.
Tks,
Bob32268

 

[69 mayflower]

I switched my 3:55 rear center section diff of my 69 Charger to a 3:23 Sure-Grip center section (8.75 489 case). Now, my speedometer is "off". I checked Classic Ind. catalog and they list the replacement gears by tooth count and color but not which rear end gear ratio that they are for. What is the correct tooth count and color for the 3:23 Sure-Grip? also, the 3:55 Sure-Grip ? Thanks in advance.
Tks,
Bob32268

I switched my 3:55 rear center section diff of my 69 Charger to a 3:23 Sure-Grip center section (8.75 489 case). Now, my speedometer is "off". I checked Classic Ind. catalog and they list the replacement gears by tooth count and color but not which rear end gear ratio that they are for. What is the correct tooth count and color for the 3:23 Sure-Grip? also, the 3:55 Sure-Grip ? Thanks in advance.
Tks,
Bob32268

 

[69 mayflower]

Rear tire size is also good information

 

[bob32268]

Rear tire size is also good information

I believe tire size is P225/70R14.....

 

[440 4 speed]

There is a formula to figure out the correct speedo gear. Involves mainly gear ratio and tire size.
Some company/site has the specs.

 

[R/T Boy 67]

If your speedometer was accurate with the 3.55s then multiply the number of teeth that the gear has by .9, and that will be the number of teeth for the 3.23s. Barring that, then search online for mopar speedometer gear chart.

 

[ckessel]

From Brewers. Same gear for 904/727's.
Speedometer Gear Ratios - Mopar A833 4-Speed Transmission & Component Specialists

 

[bob32268]

Thanks for the info and the chart, great info.
Bob32268

 

[hofferwood]

Here too.

 

[Jerry Hall]

Looks like with your current tire size, that you are wanting a 33 tooth gear. Your rear tire diameter is slightly over 26" depending on make.

 

[kiwigtx]

..........Your rear tire diameter is slightly over 26" depending on make.

....and on the number of substantial burnouts completed.

 

[bob32268]

Here too.

View attachment 1758563

Thank you, good info to have.
Bob32268

 

[bob32268]

....and on the number of substantial burnouts completed.

These new tires are too damn expensive to be doing many burn-outs or holeshots, over $300. each for Redlines, RWL's about the same.....
Bob32268

 

[bob32268]

Looks like with your current tire size, that you are wanting a 33 tooth gear. Your rear tire diameter is slightly over 26" depending on make.

Thank you for the info as to tire size and tooth count. On the GM trannies it goes by rear end gear ratio and wheel size.
Tks,
Bob32268