How many Toothed Gear?

9

97fxdwg

New Member

May 7, 2004

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Jan 16, 2006

#1

• Jan 16, 2006

• #1

I had new gears plus posi put into my rear end recently so of course my speedo is wildly off. All other things being equal (tires,etc.), what should I go with for my gear (19 teeth?) at the tranny changing from stock 2.80 to 3.50's (or was it 3.55's?). Project is a mostly-stock 68 coupe 302 with a 3-speed automatic.
Thanks for the help and sorry for the vague-ness.
:SNSign:

 

H

hrspwrjunkie

Member

Dec 15, 2004

165

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18

Jan 16, 2006

#2

• Jan 16, 2006

• #2

There are probably a number of utilities on the internet for this purpose, but this is the only one I can think of off the top of my head: http://www.hanlonmotorsports.com/t5speedo.asp

That should be able to help you with your choice. You will need to know the number of driveteeth on the transmission's mainshaft, but that should be able to help you find what you need.

Ryan

97fxdwg said:

I had new gears plus posi put into my rear end recently so of course my speedo is wildly off. All other things being equal (tires,etc.), what should I go with for my gear (19 teeth?) at the tranny changing from stock 2.80 to 3.50's (or was it 3.55's?). Project is a mostly-stock 68 coupe 302 with a 3-speed automatic.
Thanks for the help and sorry for the vague-ness.
:SNSign:

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rbohm

Founding Member

Apr 12, 2002

6,698

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204

tucson,az

Jan 16, 2006

#3

• Jan 16, 2006

• #3

what size tires are you running?

 

9

97fxdwg

New Member

May 7, 2004

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Jan 16, 2006

#4

• Jan 16, 2006

• #4

235-60-15's

 

rbohm

Founding Member

Apr 12, 2002

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tucson,az

Jan 16, 2006

#5

• Jan 16, 2006

• #5

you need a 20 tooth gear.

 

67coupe351w

New Member

Jan 31, 2004

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Portland, OR

Jan 16, 2006

#6

• Jan 16, 2006

• #6

You were a little unclear as to what your old number of teeth were but if everything else is equal aside from your gear swap and you speedo was accurate before, the easist thing to do is to (3.5/2.8)=(new# teeth /old # teeth) ---> New # teeth = 1.25* Old # teeth. then buy the closest gear availible to this number.

 

9

97fxdwg

New Member

May 7, 2004

105

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0

Jan 16, 2006

#7

• Jan 16, 2006

• #7

Thanks......

Thanks guys - I appreciate the help!

 

mfp4073

Founding Member

Mar 14, 2001

387

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38

Hells Ditch, FL

Jan 16, 2006

#8

• Jan 16, 2006

• #8

Those gears used to be fairly cheap and easy to replace. I just bought 4 or so and replaced them and checked them with either another car or one of those roadside "radar checks" (there is one near my house).