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Jul 21st, 2025 | | | | Joined: May 2009 Posts: 107 Shop Shark | | Shop Shark Joined: May 2009 Posts: 107 | Hi all,
I was wondering if you could convert a SM420 4 speed from floor shift to column (3 on the tree)? Or is there any other transmission with a non sync 1st 7.05:1 spur gears that give it that unique sound?
Thanks for what ever help you can provide!
Steven
Take care,
Steven
No one can drive us crazy unless we give them the keys.
| | | | | Joined: Dec 2015 Posts: 2,061 Big Bolt Forum Moderator | | Big Bolt Forum Moderator Joined: Dec 2015 Posts: 2,061 | I have never seen any conversion. Column shift us a complete different style transmission. | | | | | Joined: Apr 2015 Posts: 336 Shop Shark | | Shop Shark Joined: Apr 2015 Posts: 336 | You can replace the 4 speed with a 3 speed, but you'll have to get the shift linkage that goes from the tranny to the shift box, the shift box and the shifter that mounts to the steering column and attaches to the shift box. You may need to change out the steering coulum if it doesn't have the tapped holes for the screws that are needed to attach the shifter to the column (unless you drill and tap 2 holes). Also, you'll need to fill in the floor where the 4 speed shifter was.
Last edited by Cablesmill; 05/28/2017 6:19 AM. Reason: Correct the mispelled word my happy fingers made when I wasn't looking.
1959 3100 Apache Fleetside
| | | | | Joined: May 2009 Posts: 107 Shop Shark | | Shop Shark Joined: May 2009 Posts: 107 | need the granny non sync. the 4 speed offers. Also gearvenders makes an od for the sm42o and not for the 3 speed.
Take care,
Steven
No one can drive us crazy unless we give them the keys.
| | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 | need the granny non sync. the 4 speed offers. Also gearvenders makes an od for the sm42o and not for the 3 speed | | | | | Joined: Mar 2010 Posts: 10,059 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,059 | Why do you want a three on the tree type shifter? They have too many moving parts which are prone to wear and are a challenge to correct.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | I agree with Carl. I hate three on the trees. Sure, it's a built in anti theft nowadays and a neat discussion point for the uninformed, but I had nothing but problems in my 70 C10 years ago despite fixing it. Never again. | | | | | Joined: Jan 2000 Posts: 731 'Bolter | | 'Bolter Joined: Jan 2000 Posts: 731 | The big advantage to column shift, as cabs got bigger and roomier in the 1950's, was not having the big stick in the floor bumping legs. Recently swapped my 3-spd for SM420 and amazed at how far left you have to move shifter for reverse. I'm not a big guy but I can't imagine a 6 ft 200 pound guy with big legs being able to get the shifter over that far.
Also, column shift seems a bit faster because your hands are already on the wheel and don't have to come off it and search for a knob with longer throws down below your line of site. Admittedly, I'm still learning the 4-in-the-floor after 35 yrs of a 3-on-the-tree i could shift in my sleep, smooth as butter.
Love the lower first two gears in the SM420, and for that reason, plus the overall heavy duty nature of it, I'm very happy with it.
Last edited by Skooter; 05/29/2017 5:01 AM.
Matthew 6:33 1952 Chevy 1/2-ton 3100 Late '55 235/SM420/torque tube 3.55 Dalton Highway survivor (using original 216) www.truckwithaheart.com | | | | | Joined: Mar 2010 Posts: 10,059 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,059 | Aren't 4 speeds top loaders? Can't see how you could ever make that to shift on the column. Maybe Deve is lurking out there. That is right up his ally.
Last edited by 52Carl; 05/30/2017 2:45 AM.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | The big advantage to column shift, as cabs got bigger and roomier in the 1950's, was not having the big stick in the floor bumping legs. Recently swapped my 3-spd for SM420 and amazed at how far left you have to move shifter for reverse. I'm not a big guy but I can't imagine a 6 ft 200 pound guy with big legs being able to get the shifter over that far. Actually, it's not that bad. I'm 6'4". around 280 lbs, never really had any trouble with the SM420. Now if you really want to talk about a cramped situation, picture a guy my size trying to drive a '71 Duster 340 with a Pistol Grip shifter. Found out the hard way that I can't put it in reverse and have my foot on the brake or gas at the same time.
Bill Burmeister
| | | | | Joined: Sep 2013 Posts: 1,288 'Bolter | | 'Bolter Joined: Sep 2013 Posts: 1,288 | LONGBOX55 said; "Actually, it's not that bad. I'm 6'4". around 280 lbs, never really had any trouble with the SM420. Now if you really want to talk about a cramped situation, picture a guy my size trying to drive a '71 Duster 340 with a Pistol Grip shifter. Found out the hard way that I can't put it in reverse and have my foot on the brake or gas at the same time."
For those that don't know, the Dusters 4 speed has reverse down and left. I've been driving mine lately and can see how this might pose a delicate problem.
Ron
1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1964 CJ5
| | | | | Joined: May 2009 Posts: 107 Shop Shark | | Shop Shark Joined: May 2009 Posts: 107 | I have a medical issue that makes the sm420 R painful so the tree option would be better for me.
My mom had a 77 dodge van she got new and sold in 89. Never had any trouble with the tree. Granfather drove a 54 GMC pickup w/ 4spd.
Both shifter options are fun to drive in my opinion, - the medical.
sm420 is a toploader.
Take care,
Steven
No one can drive us crazy unless we give them the keys.
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Perhaps heating and bending the shift lever to a more comfortable position would work for you?
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Mar 2004 Posts: 6,189 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,189 | Whay size is your truck and what engine do you have? If you really need the Granny Gear and shifting is painful, maybe you should find an Allison automatic truck transmission. Mike B  | | | | | Joined: May 2009 Posts: 107 Shop Shark | | Shop Shark Joined: May 2009 Posts: 107 | a 66 c10 1/2 ton sb.
283ci
i'll take a look at the Allison auto....
tx,
steven
Take care,
Steven
No one can drive us crazy unless we give them the keys.
| | | | | Joined: Apr 2005 Posts: 7,442 Bolter | | Bolter Joined: Apr 2005 Posts: 7,442 | Better have a fat wallet for the Allison.ðŸ›
Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | There are other 4 speeds that will fit and have other reverse shifter positions-435, 465.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jan 2010 Posts: 378 Shop Shark | | Shop Shark Joined: Jan 2010 Posts: 378 | Why would you want to get rid of the 4-speed? Just asking. | | | | | Joined: May 2009 Posts: 107 Shop Shark | | Shop Shark Joined: May 2009 Posts: 107 | I wish someone like gear venders made a gearbox for the 3 on the tree....
Take care,
Steven
No one can drive us crazy unless we give them the keys.
| | | | | Joined: Jul 2015 Posts: 203 'Bolter | | 'Bolter Joined: Jul 2015 Posts: 203 | Someone will have to pry my T5 out of my cold dead hands someday. Having said that, why not look at a 200-R4 or 700-R4 automatic?
1953 GMC 1-Ton Pickup with 350 and 700R4
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