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Thread: rear end gear swap questions

  1. #11
    VCVC Member jrinaman's Avatar
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    I have heard of a couple second gens with 308's bit the 336 is much more common. 10 bolt posi isn't as common either. swapping first to second requires moving the spring perches. keep I mind that these are all 50 years old, a low milage 308 probably doesn't exist.
    '64 chevy, 292 40 over, 206/526 cam, 2004r trans. 9.75:1, dual webbers, Langdon cast headers, 1.94 valves

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    Sometimes low milage still show up bought a 67 parts van couple years back 42K sad part was kids had shot it full of holes. Rear end ended up in fathers hot rod
    1964 gmc handi vortec ls 5.3 whipple supercharger supter t-10 4 speed 9" ford builder of the first saturn power steering set up

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    Rear End gear question

    Quote Originally Posted by Vanner68 View Post
    You can identify the axle by the cover. Scroll down in this link to find GM axles.

    http://www.differentials.com/technic...dentification/
    Perfect for an issue I was working - thank-you for the link
    Gary
    1965 Display

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    VCVC Member joyrde's Avatar
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    a simpler swap would be an OD tranny and tall tires

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    Yes

    Quote Originally Posted by joyrde View Post
    a simpler swap would be an OD tranny and tall tires
    Yes, I agree.

    I've done both of those swaps and still I want more, but it will cost me. I've been running 215-70 15 Michelin Defenders on all four corners and a Saginaw 3 speed with Borg Warner OD. As far as the rear axle, I started with a 3.08 and when that started making noise, swapped it out with an available 3.23. I lost about 1 mpg on the highway with that change. I'm convinced that the best way to get good fuel economy with these six cylinder engines is to keep the engine speed nice and low so for me "more" would be a 2 series carrier with a ratio numerically smaller than 2.54. I haven't checked what's available since it's a project so far down the road.
    108VanGuy...
    1969 Chevy Panel, 250 CID, 3 Spd.with OD, 3.36 "WedgieVan" Daily Driver
    1967 Chevy Panel, 230 CID, 3 Spd. 3.36 "UtiliVan" 292 TFI coming. Owned since 76
    1964 GMC Panel, 194 CID, 3 Spd. "CrunchoVan"
    1965 GMC HandiBus Custom, 194 CID, 3 Spd. "MilkVan" Seized Engine
    1965 Chevy Panel 350 CID, 3 Spd. "RustoRoof" Runs but wiring bad
    1969 Chevy 108 Display 307 CID THM 350 Power Brakes 3.73 Posi
    1965 Chevy Panel, V8, 3 Spd. "Gold Hills Van" Best body of my 65s
    1965 CamperVan, V8, 3 Spd.

  6. #16
    VCVC Charter Member Vanner68's Avatar
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    Quote Originally Posted by 108VanGuy View Post
    Yes, I agree.

    I've done both of those swaps and still I want more, but it will cost me. I've been running 215-70 15 Michelin Defenders on all four corners and a Saginaw 3 speed with Borg Warner OD. As far as the rear axle, I started with a 3.08 and when that started making noise, swapped it out with an available 3.23. I lost about 1 mpg on the highway with that change. I'm convinced that the best way to get good fuel economy with these six cylinder engines is to keep the engine speed nice and low so for me "more" would be a 2 series carrier with a ratio numerically smaller than 2.54. I haven't checked what's available since it's a project so far down the road.
    108VanGuy...
    Oh, maan- my 86 Dodge has a 2.73 gear with a 318.... godawful gas mileage and could not top 80mph even with miles of straight, level road... I put an Edelbrock top end on it and got a big increase in top end and mileage... the stock 318's HP and torque were on par with a 230 inline six and the weight would be somewhere below a 'fully loaded by Mark' early. I just don't know if a six is going to have the beans to run at freeway speeds geared that way, unless the trans had a super low first gear to get rolling. A Saginaw first gear and a 2.43 rear would make for 0-60 times measured with a calendar, lol.
    Gregg Groff


    There's no place like 127.0.0.1

    1968 Chevy G20 108 panel Now with 454 power!

    1965 Chevy G10 panel- OHC Pontiac inline 6

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    Wide Ratio

    Gregg is so right, that's why I favor the Saginaw with the three ring input shaft and BW OD. That gives me a trans ratio of 3.50 in first gear and .67 in overdrive. That's as low as I can easily go in 1st gear and as high as I can go in OD and stay with the stock transmission linkage and driveshaft. With that combination, I can do 80 mph if I don't mind dropping my fuel economy by 3 or more mpg. There is still some slipping of the clutch from a dead stop, especially when you're hauling 2,000 lbs of rally related gear from Branson. Once you're at that speed with a ton of pots and pans is when you can truly appreciate the M1D effect on the brake pedal.
    108VanGuy...
    1969 Chevy Panel, 250 CID, 3 Spd.with OD, 3.36 "WedgieVan" Daily Driver
    1967 Chevy Panel, 230 CID, 3 Spd. 3.36 "UtiliVan" 292 TFI coming. Owned since 76
    1964 GMC Panel, 194 CID, 3 Spd. "CrunchoVan"
    1965 GMC HandiBus Custom, 194 CID, 3 Spd. "MilkVan" Seized Engine
    1965 Chevy Panel 350 CID, 3 Spd. "RustoRoof" Runs but wiring bad
    1969 Chevy 108 Display 307 CID THM 350 Power Brakes 3.73 Posi
    1965 Chevy Panel, V8, 3 Spd. "Gold Hills Van" Best body of my 65s
    1965 CamperVan, V8, 3 Spd.

  8. #18
    VCVC Charter Member Vanner68's Avatar
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    I've got one of the three ring Saginaw 4 speeds laying around, had considered using it in the 68 until the big block went in.
    Gregg Groff


    There's no place like 127.0.0.1

    1968 Chevy G20 108 panel Now with 454 power!

    1965 Chevy G10 panel- OHC Pontiac inline 6

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