Speedometer Driven Gear and Drive Gear?

[bill3rail]

Are the drive gear and driven gear paired up?
In other words...
Can I just change the driven gear to get my speedometer to read faster than it was?

If I change the driven gear, will the change work or will the gears not mesh correctly?

My speedometer was off by quite a bit, at 65 I was reading 50. GPS is a wonderful thing to test this!

Thank you,

Bill





3987917 17 tooth
3987918 18 tooth
3987919 19 tooth
3987920 20 tooth
3987921 21 tooth
3987922 22 tooth

[geezer#99]

You can play with different gears or just use a ratio adapter. Look here in the speedo section.
https://transmissioncenter.net/shop/

[bill3rail]

Originally Posted by geezer#99

You can play with different gears or just use a ratio adapter. Look here in the speedo section.
https://transmissioncenter.net/shop/

There is some sort of box between the speedometer cable and the driven gear bullet, but it does not look like the ones on that site.

Should I remove it to see if it is a ratio adapter?

Bill

[geezer#99]

The older ones looked different and some had changeable gears.
Take it out and then check your speedo.
It might get worse, it might get better.
All you might need is a driven gear change.

[bill3rail]

Originally Posted by geezer#99

The older ones looked different and some had changeable gears.
Take it out and then check your speedo.
It might get worse, it might get better.
All you might need is a driven gear change.

Actually, I swapped the gear but it was raining and did not take it out of the garage yet. If the rain stops, I will try it tomorrow both with and without the ratio adapter.

Bill

[bill3rail]

Started with a 20 tooth from previous owner.

Tested it with 18 tooth and it was further off.

Put in a 22 tooth and it was closer. ~10mph lower reading at 55 on GPS.

The 23 tooth gear diameter was too large to fit!?!?

I will try to get the gear ratio and tire size to figure out exactly what gear combination I need.


Bill

[hdff]

https://transmissioncenter.net/shop/...ar-calculator/
Good info here. I changed my driven gear and came real close to actual speed

[bill3rail]

Looking at the online calculators, most are asking for "Speedometer Revolutions Per Mile".
How can I figure this out? I have an L6 with stock 6cyl. in dash Chevy speedometer 6468321.

Bill

[geezer#99]

Originally Posted by bill3rail

Looking at the online calculators, most are asking for "Speedometer Revolutions Per Mile".
How can I figure this out? I have an L6 with stock 6cyl. in dash Chevy speedometer 6468321.

Bill

Use what's there. IIRC it's normally 1000.

Looks like you might need to change your drive gear since the driven gears won't get you close. That can be a lot of fun if you've never done one before.

I find it easier just to use a ratio adapter.
But to each his own!

[bill3rail]

Originally Posted by geezer#99

Use what's there. IIRC it's normally 1000.

Looks like you might need to change your drive gear since the driven gears won't get you close. That can be a lot of fun if you've never done one before.

I find it easier just to use a ratio adapter.
But to each his own!

Thank you for the 1000.

The truck had a ratio adapter on it, which I removed. After removal, it became closer to GPS reading.