Gary Best Posted September 18, 2018 Share Posted September 18, 2018 What option are available to reduce rear gear ratio to around 3.50 to 3.73? Car in a 1940 Special completely stock. Can you use gear out of early Buicks with auto transmission ? Link to comment Share on other sites More sharing options...
Morgan Wright Posted September 18, 2018 Share Posted September 18, 2018 change your 6.5 x 16 tires to 255 / 85 / 16 1 Link to comment Share on other sites More sharing options...
Leif Holmberg Posted September 18, 2018 Share Posted September 18, 2018 You can use those Buick parts up to 1955 and get a ratio as you are asked for. .From 1956 it`s another splines on the pinion shaft. Leif in Sweden. 1 Link to comment Share on other sites More sharing options...
Gary Best Posted September 18, 2018 Author Share Posted September 18, 2018 8 minutes ago, Leif Holmberg said: You can use those Buick parts up to 1955 and get a ratio as you are asked for. .From 1956 it`s another splines on the pinion shaft. Leif in Sweden. Thank you very much. I was asking for a friend in Sweden ?. Small world . He just bought a 1940 Special Convertible. 1 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted September 18, 2018 Share Posted September 18, 2018 3 hours ago, Gary Best said: What option are available to reduce rear gear ratio to around 3.50 to 3.73? Car in a 1940 Special completely stock. Can you use gear out of early Buicks with auto transmission ? Gary, my understanding is that gears up through '55 will interchange. I installed a '55 3.36 in my '50. Good for about 650 rpm reduction in third gear.. Ben 2 Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted September 19, 2018 Share Posted September 19, 2018 Yup, I went for a 3.6 on my 1940 Super. Runs good! Cheers, Dave 2 Link to comment Share on other sites More sharing options...
Buicknutty Posted September 19, 2018 Share Posted September 19, 2018 I'll chime in here too. I have a '41 Roadmaster that had the stock 3.9's in it, and was able to get a set out of a '55 Century that are about 3.4. A tiny bit less pulling power at low speeds, but much more comfortable cruising at higher speeds. Not nearly as much engine noise either. Buick rear gears will interchange from 40 to '55, but it is a lot of work, at least in my opinion. There are various instructions available, and I believe that it has been posted on the forum here somewhere. I had a shop do mine, as I was suffering from some issues with my arm at the time and wanted to get it done. I very much recommend this upgrade, if you like to drive your car very much. You will also need to either get a unit to drive the speedo at the correct rpm, so that it reads correctly, or figure out what the corrected speed is with a GPS. Your speedo will read lower than the actual road speed. Keith 1 Link to comment Share on other sites More sharing options...
Gary Best Posted September 19, 2018 Author Share Posted September 19, 2018 32 minutes ago, Buicknutty said: I'll chime in here too. I have a '41 Roadmaster that had the stock 3.9's in it, and was able to get a set out of a '55 Century that are about 3.4. A tiny bit less pulling power at low speeds, but much more comfortable cruising at higher speeds. Not nearly as much engine noise either. Buick rear gears will interchange from 40 to '55, but it is a lot of work, at least in my opinion. There are various instructions available, and I believe that it has been posted on the forum here somewhere. I had a shop do mine, as I was suffering from some issues with my arm at the time and wanted to get it done. I very much recommend this upgrade, if you like to drive your car very much. You will also need to either get a unit to drive the speedo at the correct rpm, so that it reads correctly, or figure out what the corrected speed is with a GPS. Your speedo will read lower than the actual road speed. Keith Thank you very much Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now