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RPM w/ gears and35's

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TXsizeK5, Sep 25, 2001.

  1. TXsizeK5

    TXsizeK5 1/2 ton status

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    RPM w/ gears and35\'s

    I have no idea what my gears are and i have 35 in bfg mud T's... when im crusin 60 maybe 65 my spedo is prolly off w/ bigger tires. The tach reads like 2400 or so in 3rd gear wich is 1:1... is there a way to tell gears by rpm at a certain speed?

    6in 87' K5 w/ 35" BFG muds.
    Kn filter

    What I need: 4.11 gears, Lim Slip Dif, Force2 Catback, rear springs , Throtle body spacer.
     
  2. marv_springer

    marv_springer 1/2 ton status

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    Re: RPM w/ gears and35\'s

    3.73's.....

    Marv
     
  3. Rockjunkies

    Rockjunkies 1/2 ton status

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  4. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    Re: RPM w/ gears and35\'s

    jack the back of the truck up and turn your tire one full turn and count how many times the driveline makes a compleat turn say it makes 3 and 3/4 turns that would mean 3:73's 4 and 1/4= 4:11's and so on

    wheeling videoshttp://community.webshots.com/user/ssmith6333
     
  5. Rebel88

    Rebel88 1/2 ton status

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    Re: RPM w/ gears and35\'s

    I would say 3.43s too. I have 3.73s and with 36x12.50s on right now it cruises at about 1800 or so.

    Later

    Have you driven OVER a Ford lately?
     
  6. TXsizeK5

    TXsizeK5 1/2 ton status

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    Re: RPM w/ gears and35\'s

    taking off its slow as [censored] and so is giving it gas in 3rd gear... it picks up really slow... So 4.11 gears would help alot ? Im thiking of getting a throtle body spacer , tru-duals, maybe a cam. That should allhelp with off the line power right.

    6in 87' K5 w/ 35" BFG muds.
    Kn filter

    What I need: 4.11 gears, Lim Slip Dif, Force2 Catback, rear springs , Throtle body spacer.
     
  7. wakedog

    wakedog 1/2 ton status

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    Re: RPM w/ gears and35\'s

    I have 35's too, when im in od at like 60 on the speedo its at about 2000, is this 3.73or 4.10??

    <a target="_blank" href=http://www.bigredjimmy.iwarp.com>http://www.bigredjimmy.iwarp.com</a>
     
  8. Rockjunkies

    Rockjunkies 1/2 ton status

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    Re: RPM w/ gears and35\'s

    It is hard to really tell, unless you pull the diff covers, or spin the tire and count etc. etc. etc. Using my formula comes out to 4.56. But that my not be what you have. There are alot of factors, most important is the true MPH. For example, if you did not change your speedo drive gear or have you speedometer recalibrated, you are probably actually doing 67.7 mph when your speedometer is reading 60 mph. And if this is the case, I would say that you more than likely have 4.11's. But if your true speed is in fact 60 mph, than you should have 4.56's. Better check just to make sure. Also, the advertised diameter of the tire my not be accurate. It could only measre out to 34" or less wich would also affect the caculation.

    Keep it simple
     
  9. wakedog

    wakedog 1/2 ton status

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    Re: RPM w/ gears and35\'s

    thanks for the help, im going to pull the cover and count them but i just wanted to get an estimate. thanks.

    <a target="_blank" href=http://www.bigredjimmy.iwarp.com>http://www.bigredjimmy.iwarp.com</a>
     
  10. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: RPM w/ gears and35\'s

    sounds like a match to my 4.10's w/ 35" MT's... approx 2 g's

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  11. TXsizeK5

    TXsizeK5 1/2 ton status

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    Re: RPM w/ gears and35\'s

    I seriusoly doubt the spedo was recalibrated and it was going between 60 and 65 didnt really check... im tkaing it to a shop this weekend and asking them to open it up and ocunt ... if i need new gears ill get em and get a auburn posi in the rear.

    6in 87' K5 w/ 35" BFG muds.
    Kn filter

    What I need: 4.11 gears, Lim Slip Dif, Force2 Catback, rear springs , Throtle body spacer.
     
  12. mudhog

    mudhog THEGAME Staff Member Super Moderator

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