Trans speedo gear number 904

[InRogue]

I read some wrong info on speedo gears a while back on my 904 as I now have a slew of wrong gears. I have now acquired a chart to show me the right gear to get. What I'm running is a 235/60-15 tire (26") with a 3.31 rear gear so I should be running a 33 tooth gear? Does the lower the speedo gear number make the speedometer run faster. Anyone know how much each tooth to mph the difference is? I presently have a 37 tooth and my speedo is running 6 mph slow according to GPS.

 

[Dana67Dart]

based on your info 6 MPH slow speedo ( Ie your GPS speed is 60 and your speedo shows 54)

At what speed did you get the 6 MPH diff?

Does the lower the speedo gear number make the speedometer run faster.

Yes

 

[InRogue]

Gps showing 46, Speedo showing 40, oh and I like that calculator

 

[Dana67Dart]

this is all based on the info you provided, but looks like you would be safe with a 33 or 32 tooth I would love to get another reading at speedo 60 and tell me what the GPS says (to validate the results) for the record, i haven't yet, but this calculator is what I will base my speedo gear purchase on when I go from 2.93 to 3.23

 

[InRogue]

this is all based on the info you provided, but looks like you would be safe with a 33 or 32 tooth I would love to get another reading at speedo 60 and tell me what the GPS says (to validate the results) for the record, i haven't yet, but this calculator is what I will base my speedo gear purchase on when I go from 2.93 to 3.23

View attachment 1715512555

Okay I found a spot to get the GPS to 60 mph and the speedo said 50 mph.

 

[Dana67Dart]

Are you sure the speedo didn't say 52?

It's much easier to get the speedo on a whole number like 60 and read the digital GPS.

By my calculations 50 and 60 is not giving 33 or 32 teeth. 52 and 60 does.

 

[abodyjoe]

i haven't yet, but this calculator is what I will base my speedo gear purchase on when I go from 2.93 to 3.23

i just went from a 2.94 to a 3.23 and used a 33 tooth gear and the speedo is dead on. running a 225/60-15 tire.

 

[abodyjoe]

Mopar Speedo Gear Chart : Drivin' It Home

Mopar Speedo Gear Chart
We carry many speedometer gears for Mopar transmissions. To determine what gear you need, use the table below. Our part #’s for mopar speedometer gears are FD0xx where xx is the tooth count of the gear.

At 60MPH, 1 tooth = 2 – 3mph.

More teeth slow the speedometer down, less teeth raise the the speedometer. Gears with 25 teeth or less require a different speedometer adapter.

Tooth count table is accurate to within 5MPH.

 

[InRogue]

Are you sure the speedo didn't say 52?

It's much easier to get the speedo on a whole number like 60 and read the digital GPS.

By my calculations 50 and 60 is not giving 33 or 32 teeth. 52 and 60 does.

Okay I'll check it tomorrow

 

[InRogue]

Okay I'll check it tomorrow

Okay....wow thats been awhile, okay did some tests with the GPS.

Speedo reads 50, GPS reads 54,


Speedo reads 60, GPS read 66

 

[oldkimmer]

2 teeth is around 5 mph. Kim

 

[Dana67Dart]

Okay....wow thats been awhile, okay did some tests with the GPS.

Speedo reads 50, GPS reads 54,


Speedo reads 60, GPS read 66

are you still running a 37 tooth gear?

 

[InRogue]

are you still running a 37 tooth gear?

No actually I had bought a 34, this is with the 34.

 

[oldkimmer]

32 will be pretty close. Kim