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| | | Forums66 Topics128,042 Posts1,055,509 Members48,424 | | Most Online14,466
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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For helping keep this great
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| | | | Joined: Jun 2008 Posts: 71 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2008 Posts: 71 | I need to know what the input speed for the factory 1938 100mph pickup speedometer is. I wish to mate it with my TH350 and need to find out if I will even be able to slow down or speed up the ratio from the transmission enough to calibrate it correctly or If i need to change my diff ratio to make up that difference, etc.. | | | | | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | All known GM speedometers read 60 mph at 1000 rpm on the input shaft.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | | | | Joined: Jun 2008 Posts: 71 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2008 Posts: 71 | you are my savior. that is wonderful information... very wonderful! | | | | | Joined: Feb 2000 Posts: 5,197 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,197 | My 37 works with a T350, the odometer is real closebut the speedometer is off a bit due to the weak magnet in the speedometer head. The odometer is geared to the cable so its a direct reading. Just gear the T350 using anyone of the speedometer calculator on the web to match your tire diameter and rear axle gear ratio, it should right on or atleast really close. Joe | | |
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