[69355]

I have the wrong speedo gears in my trans. My rear gears are 3.73, Do i need to change the metal gear on the input shaft or just the plastic one on the cable???

 

[Mike]

Not near enough info to answer that one.
Might just need the driven gear but depends on what drive gear is in there now.
Have some info:
http://chevelleengineer.home.comcast.net/~chevelleengineer/speedo.htm
http://www.chevelles.com/shop/speedo.html

 

[JB SS 396]

Here is another site that may help you.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#400

I have a TH350, 28" tires and 3.73 gears and my speedo gears calculated to 8 teeth on drive gear and 21 driven.

Plug in your current drive gear and see if the calculator gives you a driven gear within the available range.

Hope this helps

 

[69355]

I finally removed my driven gear, it is a orange color 35 tooth gear, and 7 gears on the input shaft. I enclosed 2 pictures to show you guys.

 

[Mike]

Still not enough info.
Check the links I posted for what you need to input to find the correct gear/s.

 

[69355]

ok, I plugged in the information, its 2.886.
LARGE SPEEDO GEARS TRANS 12 AND 13
SPEEDO 35 AND 38


SMALL SPEEDO GEARS TRANS 8
SPEEDO 23

 

[Mike]

Sounds like you need to change both gears to get the ratio you need.
Alternative is to have a speedometer shop build you a ratio adapter.
This way you don't need to pull the tail housing to change the drive gear.

 

[69355]

what speedometer shop would build one? Does that adapter go between the tail shaft and the cable?

 

[hpsherlin]

I went to a local tranny shop.
The speedo was 20 mph fast after changing from a 2.73 to a 3.42 gear set in the rear.
The owner of the tranny shop put a driven gear like you are showing with more teeth in the tranny and said "try it out". I had a hand held GPS to show MPH.
Still fast. Drove back and he put another in with more teeth..another drive...still a little fast...another more teeth gear and another drive.
More time to let headers cool off than to change that sucker.
4 mph fast now and the speedo works well. He didn't have any with more teeth and I said the 4 mph fast was just fine.
$20 total cost.
Try out a local long time tranny shop that is private owned and you might get the same service, hopefully.