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| | | Forums66 Topics128,161 Posts1,056,956 Members48,458 | | 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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| | | | Joined: Nov 2010 Posts: 12 New Guy | | New Guy Joined: Nov 2010 Posts: 12 | I have a 48 one ton and I would like to change the gear ratio so I can drive highway speeds, any suggestions or hints?? It's an ex-ambulance with low mileage but I will be upgrading to a 261 later on. Your help is appreciated, http://profile.imageshack.us/user/fraser88/ | | | | | Joined: Apr 2005 Posts: 396 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 396 | HO52/72 4.11 gearset from a 1967-1972 chevy 3/4 -1 ton, auto trans will get you to 65 MPH.
Jerry
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | The most common fix is to install the "pumplin" from a 1967 to 72 3/4 Ton truck with an automatic. They had a ratio of 4:10. I did this swap and I can drive at 60 mph with no problem. I also have tall 16" tires on mine. Here is a writeup on the procedure: Old GMC.com Site Article | | | | | Joined: Nov 2010 Posts: 12 New Guy | | New Guy Joined: Nov 2010 Posts: 12 | Thanks for your help, I'll track down a 67 to 72,,, | | |
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