Need speedo gear for 3.73's cannot find

Morales · Jul 4, 2005

Hi guys...

I have a 92 notch w/ 5-speed and a few weeks ago i put in 3.73 gears. Of course my speedo is off and i need the right speedo gear. Does anyone have any idea where i can pick one up? I checked 50resto but for some reason 3.73 doesnt show up for my year. How hard is it to install once i get it?

Michael Yount · Jul 4, 2005

http://www.geocities.com/mgnedell/notchback/tech/speedo.html

Morales · Jul 4, 2005

ok, so i need to pick up Jeep Part #j3167393

any idea how much that runs?

tjm73 · Jul 4, 2005

You can order the 23 tooth speedo gear from Steeda or 5.0 Resto or just about any larger performance supply house for about $16.

http://www.steeda.com/store/-catalog/speedometer.htm

9250stang · Jul 4, 2005

50resto will pretty much have any part you'll ever need.

tjm73 · Jul 4, 2005

9250stang said:
50resto will pretty much have any part you'll ever need.

Yeah I tried to get a link to their speedo gears page, but their site seems to be running real slow at the moment.

9250stang · Jul 4, 2005

tjm73 said:
Yeah I tried to get a link to their speedo gears page, but their site seems to be running real slow at the moment.

Their site has been down a lot lately. Keep getting a "Session time out error".

Even still, they have great service and great stuff.

tjm73 · Jul 4, 2005

9250stang said:
Their site has been down a lot lately. Keep getting a "Session time out error".

Even still, they have great service and great stuff.

Maybe updating the site?

I'm on their a lot looking at what they have for little things to keep my convertible in top condition.

Deleted member 87397 · Jul 4, 2005

speedo gear size is also going to depend on what size wheels and tire you have too, not just your gears. Follow this link and you can input gear ratio, tire height and drive gear teeth and it will calculate the number of teeth you need.

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

04sleeper · Jul 4, 2005

Try Here. Link works for me.
http://secure.50resto.com/product1.cfm?SID=1&Product_ID=226&Category_ID=145

tjm73 · Jul 4, 2005

fastfox86 said:
speedo gear size is also going to depend on what size wheels and tire you have too, not just your gears. Follow this link and you can input gear ratio, tire height and drive gear teeth and it will calculate the number of teeth you need.

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

Good point. I was assumeing he was using stock size tires, which would make those gear charts correct, but like you said a change in axle ratios PLUS a change in tire size, changes the gear needed.

That link is very good, but here's the formula to figure it out yourself as well. It's actually two formulas. It looks complicated, but it's not. I'll write it like you would put it in Excel.

Tire Rotations per Mile ( TRpM ) = 5280 / ((((((Cross Section x ( .01 x Sidewall ) x 2 ) / 25.4 ) + Wheel Diameter) x 3.14 ) / 12)

Example; TRpM = 5280 / ((245 x .45 x 2 / 25.4) + 17) x 3.14 / 12 = 785.728. So, TRpM = 785.728

That's the hardest part. And it's really not that bad.

To figure your speedo gear, you plug that TRpM into this much simpler looking formula.

Speedo Gear Needed (SGN) = Tranny Drive Gear x Gear Ratio x TRpM / 1000

Example; SGN = 8 x 3.73 x 785.728 / 1000 = 23.45 = SGN

Let me know if yopu have questions.

Morales · Jul 4, 2005

Got it from steeda couldnt find it on 50restro.com, no worries Steeda is just an hour and a half away, which means i'll get it in the mail pretty fast.

wildstang87 · Jul 4, 2005

so my 87 5speed with 245/45/17s, and 3.73s should also be a 23 tooth? b/c it give me 23.4.

Fishhawk · Jul 4, 2005

You can get the speedo gears right from your local Ford dealer

tjm73 · Jul 4, 2005

wildstang87 said:
so my 87 5speed with 245/45/17s, and 3.73s should also be a 23 tooth? b/c it give me 23.4.

No. Not all 5 speeds have the 8 tooth drive gear. '87's have a 7 tooth drive gear. Change the 8 to a 7 and you get 20.5, so you need a 20 or 21 tooth. Either is fine and will get you close enough.

tjm73 · Jul 4, 2005

Fishhawk said:
You can get the speedo gears right from your local Ford dealer

True, except you can not get the 23 tooth gear from Ford.

Need speedo gear for 3.73's cannot find

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