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  1. #1
    RC Champion
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    Question how do you install the 72t spur gear?

    hey guys how do you install the 72t spur gear?

    my guess so far is to raise one end of the transmission?
    thank you
    summit /mustang /stampede-2s spc lipo

  2. #2
    RC Turnbuckle Jr. jamann's Avatar
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    You have to clearance the "well" on the chassis.as in grind out some of the material to allow the spur to fit.raising the trans will change the driveline angles causing other issues to develop


    Sent using lipo power
    Mountains cant stop me
    they have tried

  3. #3
    RC Qualifier
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    Why would you want to do this? Just gear down pinion. I think you can go as low as 11 or possibly 10tooth. If thats not slow enough then maybe the summit doesnt suit your application. A 12tooth with 68 spur would give you a similar ratio as your stock 14t with 72t spur.

  4. #4
    RC Turnbuckle Jr. noir 522's Avatar
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    Just dremel the chassis bout 4 mm
    MAN, Use Common Sense
    Funky Gecko, SumVee HDE

  5. #5
    RC Competitor
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    Pinions are available below 10t. RR makes them to 8 I believe. I have a 9t on one now. You do have to space motor back slightly to use them but you don't have to cut the chassis any.

  6. #6
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Just imagine the torque of a 8 tooth pinion and a 72 tooth spur...
    Whatever it is I just said... I could be wrong.

  7. #7
    RC Champion
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    yes i know^^^^^^

    plan is to be able to go to 11/72 for crawling......i havent summited in what it seems to be yaers(about a year now)
    most of what i will be doing is on dried dirt.....the type of dirt piles you get in construction site areas where it is hard as rock but crumbles easly....

    seems simple enought to do. thank you guys
    summit /mustang /stampede-2s spc lipo

  8. #8
    RC Champion
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    ok just got the big 72t spur last night.....so far so good the gear was rubing the trans case just the sligtest bit. do to the spur haveing a minor offset twords the transmission other then that still need to dremel up or cut the chassis

    hay noir 522 when you dremel the chassis is there still material under the spur or is it cut back untill the spur dosent touch the chassis


    thanks guys
    summit /mustang /stampede-2s spc lipo

  9. #9
    RC Turnbuckle Jr. noir 522's Avatar
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    I cut approx 2mm deep into the chassis. The center drive shaft is now visible but I have about 3-4 mm clearance between it and the spur gear . So there is complete a hole/cut from the center of the chassis to the edge of the battery box. there is still a little chassis left on the opposite side of the spur gear (near the battery box - which is still intact.) If I were to cut there another 2mm I would be into the battery box. I have at least 2 - 3 mm of free space all around the spur gear.

    I used two 5mm spacers to push the motor back in order to fit a 8 tooth pinion gear

    NUMBERS VIA CALCULATION :

    gear ratios

    stock (14t pinion : 68t spur)
    --------------
    high gear 25.34:1 - top speed 24.54mph
    low gear 70.18:1 - top speed 8.86mph

    MY Truck -SumVee HDE (8t pinion : 72t spur)

    --------------
    high gear 46.90:1 - top speed 13.25mph
    low gear 130.0:1 - top speed 4.75mph


    half the speed , DOUBLE THE TORQUE


    actually its about 17mph in high gear (tekin brushless on 4s lipo) - I rarely go more than 4 mph in low gear - the low gear really HOWLS when you push it fast.

    Hope that helps
    MAN, Use Common Sense
    Funky Gecko, SumVee HDE

  10. #10
    RC Champion
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    okay got the 72t spur on last night....silly me only had a ezacto knife ,little sloted screw drive and a mini hammer....defenently recomend a dremal ...must of took me about an hour to get it right....

    but i have found another problem that needs to be moded .the the lower wall of the motor mount hits the spur gear...
    and note cast aluminum and wire cutters are dangerious.... so i am going to take them dremal to it when i get a chance


    everything seems to be going good sofar with the exception of the motor mount
    summit /mustang /stampede-2s spc lipo

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