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| | | Forums66 Topics128,108 Posts1,056,227 Members48,436 | | 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
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Oct 2011 Posts: 36 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2011 Posts: 36 | I finally have my 51 one the road only to find out that the 4 speed transmission whines and vibrates like crazy! I know that rebuild kits are available, but what about replacement gears. Does anyone know a source for parts for a tranny rebuild? | | | | | Joined: Aug 2012 Posts: 566 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 566 |
"As I lay rubber down the street, I pray for traction I can keep, but if I spin and begin to slide, please dear God protect my sweet ride." -Amen 56 Chevy 3100 | | | | | Joined: Oct 2011 Posts: 36 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2011 Posts: 36 | Thanks. I'll see if that is theright transmission.
| | | | | Joined: Sep 2006 Posts: 3,596 'Bolter | | 'Bolter Joined: Sep 2006 Posts: 3,596 | The transmission in your truck unless modified will be the SM 420 which was offered from 1948-67. There is a member here who completely rebuilt his with NOS parts and they are available. Novak rebuilds a lot of these transmissions and has upgrades available to make them bulletproof. Here is a step by step slide show of the rebuild process. https://www.flickr.com/photos/advance-design_parts_co/sets/72157632620943718/ | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 |
Brad,
Do you know the manufacturer and model number for the 1947 and earlier (41/42-47, I think) 4-speed transmission?
In another thread: "Before 1947 1/2 GM used the non-synchronized 4 speed SM420, as a new feature in mid 1947 (about May)the SM420 added the synchronized 4 speed, but still called an SM420."
| | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | SM420's seldom cause vibration or noise. It is much more likely you need pinion bearings, torque tube bushings, and rear U' joint yoke.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Sep 2006 Posts: 3,596 'Bolter | | 'Bolter Joined: Sep 2006 Posts: 3,596 | I will look Tim, I have lots of AD stuff but not as much on the 41-46 models. | | |
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