Speedometer question

[round_midnight]

I have a TKO 600 transmission and an Autometer speedometer. The speedo cable plugs into the transmission case near the back and has a gear that engages with something inside the tranny. I am going to change to a different rear end ratio (3.15 to 3.73 or 3.91). How do I get the speedometer to read correctly with the new rear end ratio? I'm guessing that I need to change the gear on the end of the cable. Correct? If so, how do I know what gear to use and where do I get it? Thanks.

[351-EM]

You hit the nail on the head. Speedometer gear swap out is a breeze and any Mustang Parts shops will have the gear that you need (i.e. 5.0 Resto, NPD, California Mustang etc). They have many gearchoices and you should be able to compensate for the rear change with no problem.

Chris

[Lowell W]

Jimi Guthrie from Standard Transmission can send you the gear you need. He'll need to know the height of your rear tires, number from the tag on your transmission and rear gear ratio. He's posted a lot on here so he'll be easy to find, and I think maybe they're also CC advertisers.

Lowell

[flwolfman]

The formula is:

(# of drive gear teeth) X (axel Ratio) X (tire Revolutions per mile)
__________________________________________________ _____
1000

Count the teeth on the gear inside the transmission where you plug your cable into. Hard to see, but should be 6, 7, or 8. Multiply that by your rear ratio like 3.91 or whaterver, times your tire revolutions per mile divided by 1000. That will tell you close to how many teeth you need on the new gear on the end of your cable. Hope this helps, Jim

[round_midnight]

Thanks for your replies everyone. Man I love this forum!

[STEVE POTTS]

Will the speedo gear from a toploader fit the tko600? Is the cable the same as well?

[Coloradocobra]

Steve,

Just made this swap myself. The TKO requires a right-hand rotation gear and the toploader uses a left-hand rotation gear so you will need to change. Ford has most of the gears. Here is a section from National Parts Depot...


LH rotation is typically used in 4sMT’s and RH rotation used
in all others (AT, T-5, TK, 3sMT). Transmissions with
the speedo cable hole on the drivers side typically use
RH rotation gears as marked above, Trans with Passenger
side holes typically used LH rotation gears. Repros are
all molded in white. Gear rotation has nothing to do with
the type code (3, 3A)

[Tony Aprile]

R-M

Try this calculator...I found it at transmissioncenter.net

http://www.sccoa.com/faq/speedgr.html

Also theres Ford Motorsport Catalog...formula and part numbers.

Tony

[zimmy]

Does anyone have a current part number for a Contemporary speedo cable? Toploader trans to Smith's replica mechanical speedo. Thanks.