Speedometer gears, ratios and woes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

D-Day · 06-19-2009, 10:58 AM

I need to get a new speedo gear for my truck for the proper speed reading...the one that was in there was 5 above, then when I acquired the speedometer gear housing for the smaller gears, and after talking at the dealer and trying to match things up, they gave me one that varies from 10-20mph over. Figure that one out...

It has 3.73 gears, 700R4 trans, and P245 R16's. I'm having an annoying time figuring this out, since it's on the backburner of problems I have to deal with before a trip coming up...if all else fails, I'll just pull the thing again and use an old GPS for a odo/speedo.

Orange77 · 06-19-2009, 11:22 AM

ever think of converting to electric speedometer? autometer (atm-5291)as well as summit(G2887-1) sell a sending unit that screws into the trans where the old speedometer cable went and wires to the new autometer gauge. the sending unit will also be able to let you use your cruise control off of it. the autometer one is 70 and the summit racing version is 49. to me it seems a hell of a lot easier just replacing the original gauges since you can easily convert them to autometers. if you decide to do this you can fit a 5in speedometer and tach in the 2 larger holes and 2 5/8 gauges in the other 4.

D-Day · 06-19-2009, 11:23 AM

Would be nice...just don't wanna chance screwing something up before the trip. Maybe afterwards.

swb85 · 06-19-2009, 02:08 PM

Go here:
http://novaresource.org/speedo.htm

This is the site I use to figure out speedometer gears, it's a great resource.

D-Day · 06-19-2009, 06:30 PM

Thanks swb, I'll give it a shot.

06-19-2009, 10:58 AM	#1
D-Day Live fast, die young Join Date: Sep 2006 Location: Northwest Ohio Posts: 293	Speedometer gears, ratios and woes I need to get a new speedo gear for my truck for the proper speed reading...the one that was in there was 5 above, then when I acquired the speedometer gear housing for the smaller gears, and after talking at the dealer and trying to match things up, they gave me one that varies from 10-20mph over. Figure that one out... It has 3.73 gears, 700R4 trans, and P245 R16's. I'm having an annoying time figuring this out, since it's on the backburner of problems I have to deal with before a trip coming up...if all else fails, I'll just pull the thing again and use an old GPS for a odo/speedo.

06-19-2009, 11:22 AM	#2
Orange77 Registered User Join Date: Apr 2009 Location: Tucson, AZ Posts: 184	Re: Speedometer gears, ratios and woes ever think of converting to electric speedometer? autometer (atm-5291)as well as summit(G2887-1) sell a sending unit that screws into the trans where the old speedometer cable went and wires to the new autometer gauge. the sending unit will also be able to let you use your cruise control off of it. the autometer one is 70 and the summit racing version is 49. to me it seems a hell of a lot easier just replacing the original gauges since you can easily convert them to autometers. if you decide to do this you can fit a 5in speedometer and tach in the 2 larger holes and 2 5/8 gauges in the other 4.

06-19-2009, 11:23 AM	#3
D-Day Live fast, die young Join Date: Sep 2006 Location: Northwest Ohio Posts: 293	Re: Speedometer gears, ratios and woes Would be nice...just don't wanna chance screwing something up before the trip. Maybe afterwards.

06-19-2009, 02:08 PM	#4
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Speedometer gears, ratios and woes Go here: http://novaresource.org/speedo.htm This is the site I use to figure out speedometer gears, it's a great resource. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD

06-19-2009, 06:30 PM	#5
D-Day Live fast, die young Join Date: Sep 2006 Location: Northwest Ohio Posts: 293	Re: Speedometer gears, ratios and woes Thanks swb, I'll give it a shot.



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