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| | | | Joined: Jan 2005 Posts: 310 Shop Shark | | Shop Shark Joined: Jan 2005 Posts: 310 | The odometer in the '51 has quit working. Of course, the '51 has an 80 mph speedo. I have a spare 90 mph speedo that I'm planning on fixing up to use. My question is are the gears in the transmission the same for the two different speedometers? Or, if I use the 90 mph speedo, am I going to wind up with a big error in its reading?
Thanks in advance for the help!
-Tim
'51 Chevy 3104 w/'56 235, 848 Head, HEI Dizzy, Corvette Cam, Split Manifold and Dual Carter YF's
| | | | | Joined: Jul 2006 Posts: 240 'Bolter | | 'Bolter Joined: Jul 2006 Posts: 240 | Don't think you will have a problem, but if you do you can take it to a speedo shop where they can make a adapter to correct the error.
You Learn more Listening than Talking
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Speedos are all calbrated for 1000 rev per mile. Any speedo will read the same.
Last edited by Wrenchbender Ret.; 02/11/2012 12:23 AM.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Sep 2011 Posts: 1,452 'Bolter | | 'Bolter Joined: Sep 2011 Posts: 1,452 | Speedos are all calbrated for 1000 rev per mile. Any speedo will read the same. It's just a matter of ratios, propshaft rev per mile tire rolling circumference & axle ratio)will dictate what speedo drive / driven gears or ratio adpater you will need to get that speedo cable spinning 1000 rpm @ 60mph!
BC
1960 Chevy C10 driver 261 T5 4.10 dana 44 power loc
1949 GMC 250 project in waiting
1960 C60 pasture art
Retired GM dealer tech. 1980 - 2022
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | The easy answer is that the 80 mph and the 90 mph speedometers will give the same reading as long as nothing else is changed.
If you have no big error now, you will have the same no big error with the 90 mph speedometer.
The same speedometer gears were used from 1948-1954 in 1/2 ton rucks using the same rear end, same transmission and same tires.
| | | | | Joined: Jan 2005 Posts: 310 Shop Shark | | Shop Shark Joined: Jan 2005 Posts: 310 | Thanks for the replies! You all told me what I was hoping to hear. My current speedo is fine (except for the odometer problem). The "new" speedo seems to be fine, so I'm going to just swap the two. There is no speedometer shop around here, so I won't be getting that involved with it.
Thanks again for the info!
-Tim
'51 Chevy 3104 w/'56 235, 848 Head, HEI Dizzy, Corvette Cam, Split Manifold and Dual Carter YF's
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