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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: Oct 2013 Posts: 34 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2013 Posts: 34 | I found a 308 posi from a mid to late '70's GM PICKUP 1/2 ton with spring perches that are same as my 49 original perches. The overall length is very close as well. The truck has the original 3 speed transmission and torque tube. Would the gearing be OK for the 3 speed transmission as is? The tires are tall thin tires on original 16 inch rims. Thanks | | | | | Joined: Oct 2013 Posts: 34 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2013 Posts: 34 | | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | It depends on your engine. If you have the original 216 it will be too high of a gear ratio to pull it. A good strong 235 might be OK with out big wheels but probably still be too high. If you had a 350 V-8 or 292 or even a 261 it would work OK.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Apr 2005 Posts: 2,098 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,098 | The torque tube transmission only works with the torque tube rear end. If you are going to use an open driveline rear end you will need a transmission that was designed for an open system. You will also need a driveshaft.
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: Oct 2013 Posts: 34 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2013 Posts: 34 | how about a 420 4 speed and a 235 rebuilt full pressure? Will this work with a 308 | | | | | Joined: Mar 2004 Posts: 6,214 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,214 | The SM420 is still a direct drive transmission with 1:1 ratio in 4th gear, just like most other manual transmissions. You might be better off with the 3.73 the seller has listed if your staying with a 6-cylinder engine. Mike B  | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | I agree with 3.73 gears, what is your intended use-that should have some input.
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 2010 Posts: 10,281 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,281 | I ran a 3.08 behind a high pressure 235/3 speed Saginaw transmission(1:1 final) with 28 inch tall wheels.
It had no issues going 70 MPH.
It had serious issues getting out of its own way in first gear with a load in it, or on a steep incline.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Feb 2004 Posts: 29,814 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,814 | Something in the 3.50 range is about as high geared as a stock 216 can handle, unless you're planning on driving downhill all the time.
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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