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Click on image for the lowdown. 
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| | | Forums66 Topics128,140 Posts1,056,776 Members48,454 | | 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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on the Internet for over 30 years! and not clogged down with Ads! Again, thanks! | | | | Joined: May 2010 Posts: 132 Wrench Fetcher | | Wrench Fetcher Joined: May 2010 Posts: 132 | I have searched to find info about the speedo drive gears in the 4 speed SM 420, and have learned that there may have been several different matched sets available. I have found gears for sale, but want to confirm what I have in there, I found this picture from Denny's post http://www.pbase.com/dennygraham/image/148256197So, does the yoke just pull out if I remove the big bolt on the end? Or will I need to remove that end cover plate too, to confirm what is in there. ? | | | | | Joined: May 2010 Posts: 132 Wrench Fetcher | | Wrench Fetcher Joined: May 2010 Posts: 132 | Thanks for the list. That will help. Does the yoke just pull out if I remove the big but on the end? Or is more involved disassembly required? | | | | | Joined: Oct 2006 Posts: 9,671 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 9,671 | Yep, just pull the bolt and the yoke will slip right off. Now removing the drive gear will be a challenge if you need to do that. They are pressed on and no room behind to get a grip with a standard bearing puller. You didn't mention why you're looking for a different gear set??? The 3100 only had one rear end gear and that was a 4.10:1.
Denny Graham Sandwich, IL
Denny G Sandwich, IL
| | | | | Joined: Sep 2001 Posts: 29,270 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,270 | 3100 Advance-Design enclosed drive-shaft ratios that might have been used with an SM420 transmission.
3100 1948-1953 4.11:1 3100 1954 3.90:1
| | | | | Joined: May 2010 Posts: 132 Wrench Fetcher | | Wrench Fetcher Joined: May 2010 Posts: 132 | I have a later drive train setup, so not sure what's in there. The engine is a 1956 235, and the SM 420 with an open drive shaft.
The need to get a speedo drive gear, and want to confirm what gear is in there to mate to. | | |
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