1940 Buick rear gears

[Gary Best]

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 ?

[Morgan Wright]

change your 6.5 x 16 tires to 255 / 85 / 16

[Leif Holmberg]

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.

[Gary Best]

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.

[Ben Bruce aka First Born]

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

[Daves1940Buick56S]

Yup, I went for a 3.6 on my 1940 Super. Runs good!

 

Cheers, Dave

[Buicknutty]

 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

[Gary Best]

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