What color speedo gear do I need?

[Michael L.]

Guys,

I have a 69 4spd car with factory 3.55 rear gear. Getting ready to install the speedo cable and trying to figure out what color gear I need to use. Is there a chart that matches rear gear ratio with speedo gear color?

Mike

[Joe L.]

Re: What color speedo gear do I need?

Guys,

I have a 69 4spd car with factory 3.55 rear gear. Getting ready to install the speedo cable and trying to figure out what color gear I need to use. Is there a chart that matches rear gear ratio with speedo gear color?

Mike

Mike-----

GM says you require a GREEN 25 tooth driven gear. However, this assumes that your transmission contains a a BLUE nylon drive gear and that you have tires of the original OD.

[Michael L.]

Re: What color speedo gear do I need?

Thanks Joe. I called the tranny rebuilder and apparently he used an 8 tooth steel drive gear. Using that number I plugged it into a formula I found online and it came back as a green 22 tooth gear. Can you tell me where you got your chart from? They're fairly cheap I could just order both just to be certain I suppose but prefer not to have to swap it out if I can avoid it.

Mike

[Joe L.]

Re: What color speedo gear do I need?

Thanks Joe. I called the tranny rebuilder and apparently he used an 8 tooth steel drive gear. Using that number I plugged it into a formula I found online and it came back as a green 22 tooth gear. Can you tell me where you got your chart from? They're fairly cheap I could just order both just to be certain I suppose but prefer not to have to swap it out if I can avoid it.

Mike

Mike-----


My information in this case comes from the P&A Catalogs.

A steel speedometer drive gear is not correct for your application although it might work OK PROVIDED THAT it's the correct 8 tooth gear AND that it's installed at the precise location. The correct nylon drive gear uses a special clip which ensures the exact placement of the gear. To work with the 22 tooth green driven gear, your drive gear needs to have an OD of 1.77". 22 tooth GREEN to 25 tooth driven gears require the 1.77" OD drive gear. 18 tooth to 22 tooth SILVER driven gears require a 1.85" OD drive gear.

[Michael L.]

Re: What color speedo gear do I need?

Thanks Joe. Apparently he always puts in the steel drives because if the speedo cable binds and locks only the easily replaceable gear gets trashed and not the internal drive gear, which apparently can be damaged and is a pain to replace. The guy that did the tranny is a respected rebuilder/restorer of trannys for all sorts of muscle cars so I'm hoping he did it correctly. He sure made the tranny look nice!

Mike

[Jeff B.]

Re: What color speedo gear do I need?

Mike:
Not sure if they are the same, but my 67 M21 4spd w/3.55 posi rear has the original factory installed driven gear. It is green, with 22 teeth.

[Duke W.]

Re: What color speedo gear do I need?

Guys,

I have a 69 4spd car with factory 3.55 rear gear. Getting ready to install the speedo cable and trying to figure out what color gear I need to use. Is there a chart that matches rear gear ratio with speedo gear color?

Mike

You need to specify the installed tire size and revs/mile spec.

Duke

[Michael L.]

Re: What color speedo gear do I need?

Thanks Duke. What I was looking for was someone with a similar set up like Jeff responded with so that I had a good starting point. I figured someone else must have had a similar setup and be able to tell me what was there from the factory, rather than try and calculate from scratch what size gear I would need. I'll start with the 22 tooth green gear and go from there.

Mike

[Bob R.]

Re: What color speedo gear do I need?

If your tires are the original size and your transmission re builder put in the correct parts the green gear should work fine. If you have radial tires a 205 75 R 15 should work correctly also.