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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Oct 2006 Posts: 12 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 12 | I have a 41 GMC. Stock 4 speed. Got it all back together and took it for a drive. The speedo doesn't work and the odometer runs backwards........ What did I do wrong??? | | | | | Joined: Mar 2010 Posts: 10,271 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,271 | Did the speedometer ever work properly before?
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: May 2015 Posts: 11,004 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,004 | Speedometer drive gear in backwards in the tranny taillshaft?
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Oct 2006 Posts: 12 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 12 | Speedo cable was not hooked up when I got truck. I have had the trans out and the tail shaft off. Didn't know I could put it in backward. | | | | | Joined: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | Are you driving in reverse, you showoff? 😉 | | | | | Joined: Mar 2014 Posts: 4,479 Moderator, Electrical Bay | | Moderator, Electrical Bay Joined: Mar 2014 Posts: 4,479 | Honestly most of the time I've seen this is because somebody at some time installed the wrong speedometer drive gear. Some point one way and others point the opposite way.
~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
| | | | | Joined: Feb 2004 Posts: 29,750 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,750 | If you disconnect the speedometer cable at the transmission and look at the end of the gear that drives the cable, it should be turning clockwise as the wheels turn in a forward direction. Jack up one rear wheel and either have someone spin the wheel by hand or let the engine idle in 1st. gear. If the gear is turning the proper direction, try the same check by disconnecting the speedometer cable inside the cab. There might be a speed change gearbox somewhere between the transmission and the dash that is assembled incorrectly.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Mar 2010 Posts: 10,271 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,271 | Is there any indication that the speedometer has been rebuilt? The last time I had one open, it looked like that it is possible to reassemble it incorrectly. I do not know if that will make it go backwards.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | Is the speedo cable attached to the drivers side?
If I remember correctly the driven gear can be installed to come out either side of the transmission. If the cable is attached to the passenger side it will turn the speedo backwards.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Oct 2006 Posts: 12 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 12 | Thanks, Ill try this first. I is on the pass. side | | |
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