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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!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Sep 2009 Posts: 6,012 Gearhead, Stovebolt Tech and Parts Tracker, Mod for Swap Meet and GTT | | Gearhead, Stovebolt Tech and Parts Tracker, Mod for Swap Meet and GTT Joined: Sep 2009 Posts: 6,012 | According to the 1955.2 Series Truck Shop Manual the speedometer drive gear is pressed onto the output shaft u-joint forward yoke. As there is no contradictory information in the 1956 Supplement, I think it's likely that your friends should also be press fit and tightening the yoke securing nut will have no effect if the drive gear is loose/moving on the yoke. A double check of the Master Parts books shows no key for the gear listed.
It is possible that the drive gear could be moving and causing the erratic speedometer function. The only way to know is to drop the drive shaft and remove the yoke to inspect. It's possible that someone could have improperly reinstalled the drive gear to the yoke. The Shop Manual indicates to be sure that the drive gear is installed with the beveled edge towards the front of the transmission. If it was installed backwards it could be improperly seated.
Let us know how you find things when you get into it.
~ Dan 1951 Chevy 3 window 3100Follow this story in the DITY Gallery"My Grandpa Carl's Truck and How it Became Mine"1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
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