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Thread: 12 bolt rear end gears

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    New Guy
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    12 bolt rear end gears

    Hi Now that I have installed a turbo 350. In my 65 flat glass I need to get some highway gears for my rear end. Thought I would order thru summit racing. Has any one done that yet I would like to know the part numbers that worked I currently have a 12 bolt from a 65. Hj1221 373. The engine races at 50 mph. Suggestions appreciated.

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    Certifiable Vanatic RAY68108's Avatar
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    An overdrive trans may have been the better choice swap...70mph @ 2000 RPM. JMTC, Ray
    Last edited by RAY68108; 04-01-2020 at 06:53 AM.
    68 108 panel parts donor
    69 108 sportvan deluxe 350 4bbl 700R4 3:36 posi
    68 108 sportvan custom 350 4bbl 700R4

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    Welcome

    Welcome aboard. Sorry, I don't know the answer to your question but I do have some of the same issues with gearing. I'm looking for 2 series carriers now. If you've already picked out the size rear tires you want and the transmission you want, then I think the rear axle ratio would be the last piece of the puzzle. The best ratio for your van would depend on the rpm you want at a given highway speed. If you know or can find out the torque curve for your engine, I'd set your preferred highway speed just above peak torque. As for the ring and pinion ratio, the most cost-effective option would be to stay with the same carrier. You probably have a 3 series carrier (?) which is the most common so 3.08 would be the highest gear set (lowest numerical) you could install on that carrier. You said the engine races at 50 mph, what is the RPM? If you're not sure or have no tachometer, be sure that "racing" is not fixed blade fan noise.
    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.

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    12 bolt rear end gears

    New gear set https://www.motivegear.com/auto-parts-catalog/ ; they have a 3.08 set...
    Gary
    1965 Display

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    VCVC Member kookykrispy's Avatar
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    our vans use "truck" 12 bolts

    Just be aware that our vans use "truck" 12 bolt rear ends.. not the car type such as found in chevelle/nova/camaro etc. When ordering parts, be sure to select "truck" if there is an option. Some parts, such as the carrier, is different "truck 12 bolt" vs. "car 12 bolt"



    64' wikivan 230/4 onda tree/2.56 posi
    '64 Red Baron no engine/trans
    '66 "Lucky" 230/3 onda tree/project

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