Speedometer Ratio Adapter - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cowboyd · 05-17-2003, 11:06 AM

Long time reader first time poster. Just thought I would pass on a little information. I recently had a 3.73 ring and pinion put in replacing a 3.08 ( also installed an Eaton Posi ) Wooo Hooo!! Anyway my spedometer was off before and the change made it read 81@55 MPH. Thought I could change the speedo gears but I was told I couldn't get that much change.

Long story short here is a company that will make any ratio reducer you want.
Leach Enterprises in Crystal Lake, Chicago ILL. ( www.leach-ent.com ) Cost was about $70 plus tax and shipping. I will post again when I get it installed.

BigRed · 05-17-2003, 12:27 PM

A buddy of mine has one of those adapaters on his truck. He had to take it off as it was leaking constantly. Thanks for the info!

ElGracho · 05-17-2003, 08:29 PM

You can get gears that will probably work with your combo of tire size and gear ratio. What I think they meant was that you can't just change the driven gear. You will have to change the drive gear too. Take a look at Swervin Ervin's site here. to get some info. If you need more help, let me know, I've sucessfully done this on about five trucks.

Cowboyd · 05-18-2003, 04:32 PM

Joe
Thanks for the reply. I've seen Mike's info before and thought I could solve the problem with the gear change. But my local GM parts guy told me I couldn't get a large enough driven gear.I sure hope he knew you can change the drive also!! If our speedometers are 1000 revolutions per mile the calculator said ther should be a combo that would work. Anyway to late for that I already orderd the reducer.

If it leaks or is still off I'll try changing the gears.

Thanks a lot, Boyd

gchemist · 05-18-2003, 09:16 PM

Try playing for the closest gear ratios you can with this web site.
http://www.tciauto.com/tech_info/speedo_gears.htm

Cowboyd · 05-22-2003, 05:43 PM

TTT

05-17-2003, 11:06 AM	#1
Cowboyd Registered User Join Date: May 2003 Location: Galena, Illinois Posts: 9	Speedometer Ratio Adapter Long time reader first time poster. Just thought I would pass on a little information. I recently had a 3.73 ring and pinion put in replacing a 3.08 ( also installed an Eaton Posi ) Wooo Hooo!! Anyway my spedometer was off before and the change made it read 81@55 MPH. Thought I could change the speedo gears but I was told I couldn't get that much change. Long story short here is a company that will make any ratio reducer you want. Leach Enterprises in Crystal Lake, Chicago ILL. ( www.leach-ent.com ) Cost was about $70 plus tax and shipping. I will post again when I get it installed. __________________ 79' C10 Short Step 355/TH375 W/3.73 & Eaton Posi 1.5"/3" Drop What I have I owe to udders!

05-17-2003, 12:27 PM	#2
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	A buddy of mine has one of those adapaters on his truck. He had to take it off as it was leaking constantly. Thanks for the info! __________________ Scott Shelbourne

05-17-2003, 08:29 PM	#3
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	You can get gears that will probably work with your combo of tire size and gear ratio. What I think they meant was that you can't just change the driven gear. You will have to change the drive gear too. Take a look at Swervin Ervin's site here. to get some info. If you need more help, let me know, I've sucessfully done this on about five trucks. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

05-18-2003, 04:32 PM	#4
Cowboyd Registered User Join Date: May 2003 Location: Galena, Illinois Posts: 9	Joe Thanks for the reply. I've seen Mike's info before and thought I could solve the problem with the gear change. But my local GM parts guy told me I couldn't get a large enough driven gear.I sure hope he knew you can change the drive also!! If our speedometers are 1000 revolutions per mile the calculator said ther should be a combo that would work. Anyway to late for that I already orderd the reducer. If it leaks or is still off I'll try changing the gears. Thanks a lot, Boyd __________________ 79' C10 Short Step 355/TH375 W/3.73 & Eaton Posi 1.5"/3" Drop What I have I owe to udders!

05-18-2003, 09:16 PM	#5
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Try playing for the closest gear ratios you can with this web site. http://www.tciauto.com/tech_info/speedo_gears.htm __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

05-22-2003, 05:43 PM	#6
Cowboyd Registered User Join Date: May 2003 Location: Galena, Illinois Posts: 9	TTT __________________ 79' C10 Short Step 355/TH375 W/3.73 & Eaton Posi 1.5"/3" Drop What I have I owe to udders!

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