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| | | | Joined: Nov 2012 Posts: 15 New Guy | | New Guy Joined: Nov 2012 Posts: 15 | Hi . My buddy has a 2 ton 53 with a sm420 trans. and an open drive shaft. I have a sm420 set up for a torque tube. Can we change the rear bearing retainer and use my trans as a replacement? His has a parking drum on the rear of the box. Are the output splines the same? Will the PTO bolt up? I guess i'll find out when it gets warm enough to pull his out. His won't stay in 2nd gear . Thanks, Chip | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Novak has 420 rebuild kits.
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: Feb 2004 Posts: 29,841 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,841 | Yes, everything ahead of the bearing retainer is the same. I got involved in the conversion recently, but the other way- - - -changing an open driveline 420 to torque tube drive. Do not discard the front universal joint yoke used with the torque tube- - - -it's unique to the 420 transmission, and it's very scarce! The joint cross and the rear yoke are the same as a 1/2 ton, but not the front!
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jan 2013 Posts: 1,518 'Bolter | | 'Bolter Joined: Jan 2013 Posts: 1,518 | Good info to pass on Jerry, I might add that if he plans to retain the parking drum and related appurtenances, of his bigbolt he will need the top loader off the original transmission unless the donor trans has the shaft for the brake handle. I have never seen a fine spline sm420 but a couple late models have them.Also even the sm420s found in 1/2 ton had a side cover pto provision that is identical. Basically sm420 from 1/2 tons on up to 2 tons are identical sans the rear bearing cover and ujoint for the enclosed driveshaft, and top cover for the hand brake.
Like Jerry says save the yoke and bell type rear bearing cover found in 1/2 and 3/4 ton trucks pre 55, getting hard to find.
Last edited by sstock; 01/17/2020 5:36 PM.
1953 Chevrolet 3100261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY GalleryVideo of the 261 running1964 GMC 1000305 Big Block V6, sm420, the next cab off restoration
| | | | | Joined: Nov 2012 Posts: 15 New Guy | | New Guy Joined: Nov 2012 Posts: 15 | Thanks for the replies. I'll keep you posted when we get into it . Baby it's cold outside! Snowing in Maryland | | | | | Joined: Feb 2016 Posts: 1,994 'Bolter | | 'Bolter Joined: Feb 2016 Posts: 1,994 | It got cold here for a couple of days, eight inches last night now raining, too sloppy to get the truck out of the barn.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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