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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!
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| | | | Joined: Apr 2015 Posts: 11 'Bolter | | 'Bolter Joined: Apr 2015 Posts: 11 | I have a 63 c10 with stock 230 and the granny 4 speed, I also have access to a 68 Saginaw 3speed with 3 grooves.
When I compare the ratios of 2nd on the granny and 1st on Saginaw, they are pretty close.
My issue with the granny 4 speed (I always start out in 2nd) is when going uphills the length of time to Shift from 2-3 or 3-4 is so long that I lose the RPM’s for the next gear to be effective and i end up downshifting to gain momentum. I’m thinking the Saginaw would allow quicker shifts in the power band rpm range and be a better option
Any thoughts or experience with this would be helpful
Schetk
| | | | | Joined: Apr 2005 Posts: 2,102 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,102 | Some things to consider: You will need to modify the drive shaft to fit the Saganaw transmission. Also, find a 3 speed column with all the rods & levers or install a floor shift conversion. The three speed does have somewhat closer ratios than the SM420 and it is fully syncronized.
Fred
1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine
| | | | | Joined: Feb 2004 Posts: 29,875 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,875 | Before you start doing major surgery, what kind of gear lube are you using in the SM-420? 90 weight straight mineral oil is the recommended lube- - - -if you're using some type of fancy synthetic gear oil, it might be so slippery the synchronizers can't get a grab on those heavy gears and you'll have to shift slowly to prevent grinding. Try flushing the transmission by filling it with Diesel fuel, idling for a few minutes in neutral, then refilling. 90 weight Ford-specification transmission oil for an 8N tractor is the correct lube, or any other straight 90 weight without hypoid additives will work OK.
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: Jul 2014 Posts: 1,293 Moderator for Tons o' Fun , Co-Moderator Driveline Forum | | Moderator for Tons o' Fun , Co-Moderator Driveline Forum Joined: Jul 2014 Posts: 1,293 | You really ought to try the mineral oil as Hot Rod suggested. For roughly $25 for the oil and whatever diesel it would take... might save you a whole lotta work.
Ron - - Dusty53 1954 Chevy 3604In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell."
"They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel." | | | | | Joined: Feb 2004 Posts: 29,875 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,875 | I saw a You Tube video a few days ago with a truck in it that was running two- - - -count 'em- - - -SM 420's in tandem, one turned backwards. The guy was using 3rd. gear on the reversed transmission as an overdrive, and 4th. was his direct drive. He had a "shift on the fly" synchronized Brownie!
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: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | Wow. That is amazing.
Last edited by Fox; 03/24/2021 5:05 AM.
| | | | | Joined: Feb 2019 Posts: 4,511 AD Addict & Tinkerer | | AD Addict & Tinkerer Joined: Feb 2019 Posts: 4,511 | I saw a You Tube video a few days ago with a truck in it that was running two- - - -count 'em- - - -SM 420's in tandem, one turned backwards. The guy was using 3rd. gear on the reversed transmission as an overdrive, and 4th. was his direct drive. He had a "shift on the fly" synchronized Brownie!
Jerry I bet the linkage on that was really interesting!
Last edited by Phak1; 03/24/2021 12:30 PM.
Phil Moderator, The Engine Shop, Interiors and Project Journals1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc BrakesProject JournalsStovebolt Gallery Forum | | | | | Joined: Feb 2004 Posts: 29,875 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,875 | He just put a couple of torch bends in the shift lever of the second transmission and cut a hole in the floorboard of the truck between a pair of bucket seats made from 30-gallon oil drums!. That project was a few levels below "Rat Rod" stage!
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!
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