FE-FC Holden Discussion Forum

Technical Board => General Technical => Topic started by: yackboy49 on February 08, 2022, 04:08:43 PM



Title: Speedo Gears
Post by: yackboy49 on February 08, 2022, 04:08:43 PM
Just trying to determine which colour speedo gear I need, trimatic behind a 202 in an FC with 13 inch wheels. Existing speed is 10 mph fast. They range from 20 teeth to 24.

Regards
YB



Title: Re: Speedo Gears
Post by: sgo on February 08, 2022, 06:44:24 PM
Best to look at what colour/teeth you have now and start  your calculations from there.


Title: Re: Speedo Gears
Post by: ipg on February 08, 2022, 07:46:12 PM
https://www.centauriaudio.com.au/tchc4878/speedocalc.html


Title: Re: Speedo Gears
Post by: sgo on February 08, 2022, 08:37:43 PM
For some reason I didn't have much success with the speedo calculators, but  I think there's a 5% difference between each cog so if you know which one you have you can easily calculate what you need, or at least which is closest?


Title: Re: Speedo Gears
Post by: Harv on February 09, 2022, 07:28:25 AM
More information is needed to answer your question.

At what speed is the speedo out by 10mph? You need to convert 10mph into a percentage in order to change the teeth ratio by that percentage.

What gears are currently in the car now? You then step up (or down) gear colours depending on what is in the vehicle. That ratio depends on both gears... not just the driven one.

Drive gears (worm gears... hard to get at):
brown: 6 teeth
I cant remember: 7 teeth
natural: 8 teeth
greenish blue: 9 teeth
yellow: 10 teeth

Driven gears (easy to get at):
pink: 19 teeth
white: 20 teeth
green: 21 teeth
dark blue: 22 teeth
red: 23 teeth
yellow: 24 teeth
light blue: 25 teeth

Cheers,
Harv


Title: Re: Speedo Gears
Post by: yackboy49 on February 11, 2022, 08:00:50 PM
thanks lads for the info, bit of homework to do.

YB