| |
Click on image for the lowdown. 
====
| | | Forums66 Topics128,035 Posts1,055,557 Members48,426 | | 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!
| | THANKS!
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: Nov 2010 Posts: 339 Shop Shark | | Shop Shark Joined: Nov 2010 Posts: 339 | Does the speedometer drive just screw into the SM420, if so does it come out easy? I have a speedometer that jumps around a lot but I think its the speedo head itself. but thought I would check the gears on the drive to make sure. 53 3100 root | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | There is a gear that can be unscrewed from the case of the transmission (to inspect the teeth). There is a gear inside the rear of the transmission and it cannot be removed without removing the u-joint yoke at the rear of the transmission. | | | | | Joined: Oct 2010 Posts: 202 'Bolter | | 'Bolter Joined: Oct 2010 Posts: 202 | It does on the SM420 on my 54 3100.
Checking the gears is a good idea. I had to use a deep thin walled socket to remove the speedometer cable drive. The other gear is held in place by the u-joint yoke. Speedometer gears rarely wear out though. The problem your having is more likely a wore out speedometer head, as was the case on my truck, or it could be the drive cable. Jim Carter Truck has refurbished original speedometer heads. I would avoid the Chinese reproductions. they also have the cables.
Walt Williams
| | | | | Joined: Oct 2006 Posts: 9,671 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 9,671 | Well Walt, I think you've miss understood what Tim replied. The 'drive gear' is pressed on to the yoke or U-joint flange and can only be removed by removing the yoke and pressing the drive gear off. http://www.pbase.com/dennygraham/image/148876672If your's slips on and off the flange then something is worn. If it were not a press fit, what would keep it from slipping on the flange when in motion? So....I believe you're thinking of the 'driven gear' which can be easily removed with a 15/16" box wrench. http://www.pbase.com/dennygraham/image/160677688dg
Denny G
Sandwich, IL
| | | | | Joined: Nov 2010 Posts: 339 Shop Shark | | Shop Shark Joined: Nov 2010 Posts: 339 | My bad, yes it is the driven gear. I will remove and check it out for damage. Thanks y'all. root | | |
|
|
| |
