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#1 |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
I have an I6 250 with a 3 speed Saginaw transmission which was converted to the floor shifter. Since getting the truck, I've been annoyed at how tall the first gear ratio is. I have to really ride the clutch for what seems to be forever to get going into first gear which just seem ridiculously tall and hard on the clutch.
I've read in a few threads that the gear ratios were different in the 3 Speeds from factory depending on your engine choice. I eventually want to go with a small block 327 or 350 and plan on keeping the 3 speed. Is it reasonably doable to change the first gear out to something less tall? Is this a common problem or does everyone just live with this really tall gear matted to the I6's?
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1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#2 |
Senior Member
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Location: Colfax-California
Posts: 8,523
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
What is the rear axle ratio? Would be easier to replace the transmission than rebuild it with a different gear set
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#3 | |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
I would hate to replace the entire tranny though, I do like the feel of the 2nd and 3rd gear
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1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#4 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
1st gear in a truck 3 speed was lower than 1st in a car 3 speed
I agree you would be better off swapping rear gears if it "bogs" or you have to feather clutch in 1st currently. You can jack up rear end, rotate rear tire 1 revolution and count how many times the drive shaft rotates to see what gear ratio you have I currently have 3:73 in my 250 3 OTT 72, was considering 3:08's as my 1st gear is low enough and the Hwy RPM would be better. YMMV |
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#5 | |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,194
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ Last edited by Keith Seymore; 11-29-2022 at 12:45 PM. |
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#6 |
Senior Member
![]() Join Date: Mar 2015
Location: washington
Posts: 2,236
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Stock, non-optioned, gear ratio for your truck is 3:73.
If the SPID is still in the glove box and it doesn't show and option for the differential that is what you should have. As with any 50 year old truck it could be anything. |
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#7 | |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
__________________
1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#8 | |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
__________________
1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#9 |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Yeah, doesn't say anything about gearing on the glove box. I'm guessing 3.73's but hope to confirm when I do the axle gasket and fluid change
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1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#10 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
beyond the different gear ratios offered for a Saginaw 3 speed, it is my understanding the trucks got the 2;85 1st gear (aka no lines) vs the 2.54
Saginaw 3-speed 1st 2nd 3rd n/a n/a Saginaw 3-speed – 1 Line 2.54 1.50 1.00 n/a n/a Saginaw 3-speed – 2 Lines 3.11 1.84 1.00 n/a n/a Saginaw 3-speed – 3 Lines 3.50 1.89 1.00 n/a n/a Saginaw 3-speed – No Lines (grooves) 2.85 1.68 1.00 n/a n/a IDK to what extent the cases or other internal parts are different, if they even are, other than the gear ratios You would have to pull trans, put in 1st and rotate input shaft and count the revolution of output shaft to see |
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#11 |
Who Changed This?
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Location: Simi Valley, CA
Posts: 10,392
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
A better way to go is to substitute a different trans, as mentioned. Should be cheaper than gutting the old one, because it's going to take a different cluster gear as well.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#12 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
another way of checking 1st gear ratio without pulling trans.
remove DS. put in 1st. Use a FW/Flexplate wrench to turn the motor 1 turn. Count how many times tail shaft turns. Or have a helper rotate engine by damper bolt and you count tail shaft turns |
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#13 |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Finally go around to doing my rear diff oil change today and did the tire spin while counting the axle spins to try and figure out my diff gearing.
I tried the one full rotation of the rear tire and counted my drive shaft rotations which didn't even get around twice which I thought was weird. I then googled a video and one guy said you have to rotate the rear tire 2 full turns to find your gear ratio which seemed to work much better. By using the 2 full turn method, my drive shaft rotated 3 full turns plus a sliver. I'd guess that to be 3.08 or 3.10 gearing. Is the two full rotation the proper way of doing it? That's pretty low rear gearing but it would explain my having to feather the clutch a lot to get going in traffic as well as the PO putting on larger tires making this worse. I was hoping for something more in the 3.73 range but don't think it's worth changing the gearing out now cause I just put $60 worth of Royal Purple in there and the diff gears looked really really nice when I opened it up.
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1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#14 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
well maybe someone swapped them to 3:08 or you have a higher gear ratio 1st gear Saginaw than the 2.85 truck saginaw
I have 3:73 and would like to swap to 3:08's but my understanding is 3:73 use a 4 series carrier and 3:08 use a 3 series carrier so I would have to find a 3 series to go 3:08 |
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#15 | |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
__________________
1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#16 | |
Who Changed This?
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Location: Simi Valley, CA
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#17 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
I never liked a 3spd transmission due to the high first gear, as well as such a wide range between gears. Making some turns in 2nd can mean lugging or slipping the clutch a bit. I just always felt they were a bit below minimal gearing, a bit deficient. Not a hater, but that has always been how I have felt. The best thing and first thing I'd do is slap a 4spd to get proper gearing. I keep a 4spd Saginaw around for just that reason, in case I end up with a 3spd truck. You already have the shifter moved to the floor, so visibly there is no change except way better driveability. The best part about it is a 4spd slips right in as if the truck already had one
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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
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#18 | |
Registered User
Join Date: Oct 2022
Location: Regina, Saskatchewan
Posts: 343
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
You're definitely right about the 3 speeds being wonky on some turns! Lol. I don't mind mine, its kinda fun to drive but having a better 1st gear would be ideal
__________________
1971 Chev C10 - 250ci L6 w/3 speed on the floor Upgrades: Power Steering 3 Core Radiator 7 Hole Gauge Cluster Power Brakes (Incoming!!..) 1971 350 (Incoming!!..) |
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#19 |
Post Whore
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Location: Portland Oregon
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
You might look to see if at some point in the past someone swapped a car transmission in. I'm no expert on these transmission (Or any transmission really) but there should be a way to determine what version you have without pulling the transmission. Casting numbers probably won't tell you what gear set is installed but there should be a tag or some stamped numbers/letters to indicate how the transmission left the factory.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#20 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
A pic of the drivers side of the transmission will help.
Could be a Saginaw or a Muncie. |
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#21 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
>>................ because guys were saying the 1st gear was useless for daily driving. <<
They were talking about a truck 4-speed such as a SM465 with a granny low. Special-k was talking about a car 4-speed.
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'67 GMC 2500, 292, 4spd, AC |
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#22 | |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
Quote:
yeah OP may have a passenger car 3 speed |
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#23 |
Senior Member
![]() Join Date: Mar 2015
Location: washington
Posts: 2,236
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
"want to go with a small block 327 or 350 and plan on keeping the 3 speed."
I would consider ignoring the transmission issue for now. Make the motor change first. The extra torque may make the whole thing mute. A modern truck five speed may be your best answer. Gets rid of the clumsy linkage and you get an overdrive. A win win. Cheers |
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#24 |
Post Whore
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
I'm afraid I don't know what you're referring to when you say "lines". Are the lines machined on the gear sets?
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#25 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 756
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Re: Saginaw 3 speed Transmission - Reasonably Possible to change 1st Gear Ratio?
My understanding is the grooves (marks) denoteing what gear ratios are on the input shaft so you would need to pull the tranny to see them.
Saginaw three-speed transmissions featured gear ratios of 2.85:1 for first, 1.68:1 for second and 1.00:1 for third when matched with L6 in-line six-cylinder engines. For small-block V-8s, like the 350, the three-speed used 2.54:1, 1.50:1 and 1.00:1. The four-speed matched with the straight-sixes were 3.11:1, 2.20:1, 1.47-to-1 and 1.00:1. For V-8s, it was 2.54:1, 1.80:1, 1.44:1 and 1.00:1. |
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