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Thread: 901 transaxle gearing and ring pinion combo question

  1. 01-15-2013, 03:31 PM #1
    RonW
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    901 transaxle gearing and ring pinion combo question

    Hey guys, frequent lurker but infrequent poster. My project 912 is a bit of an odd duck to say the least which some may have seen around. Basically, I'm trying to change my final drive for higher speed freeway cruising. Right now I have the stock '68 901/902 5 speed. I've swapped in 3rd/4th/5th(ZD) from a 914. the ring pinion is 7:31 (4.29). with my 205/15 I am doing about 63 mph at 3000 rpm and for CA traffic, that's kinda slow but I get 30 mpg. as soon as i bump up to 3400 rpm it bumps me up to 75 mph but then i drop to 24mpg (and on boost as well). I have another good standard 901 4 speed in the garage a friend gave me and wondered if the ring and pinion that is found in the 4 speed sportomatic, 7:27 (3.857), would swap in? then i'd just put in a ZD 5th and be able to cruise at 75mph at 2900 rpm or 65mph at 2600rpm.
    Last edited by RonW; 01-15-2013 at 03:39 PM.
    68 912 - R inspired - 2.0L-4 turbo 18psi
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  2. 01-18-2013, 01:17 PM #2
    davep
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    Sportomatic diff will not fit in a manual transmission.
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  3. 01-20-2013, 08:35 PM #3
    RonW
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    alright thanks. thats answered my question and guides my next steps
    68 912 - R inspired - 2.0L-4 turbo 18psi
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