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Gears, anyone?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fbronson, Feb 25, 2004.

  1. fbronson

    fbronson 1/2 ton status

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    My '83 K5 and I are both new to the world of modifications, and I have a question concerning finding the right gear ratios for the axles. Recently, I installed a 4" lift and 33X12.50's. Everything else in the driveline is stock... this translates to 6.2L, 700R4, and GM 10 bolt axles, front and rear. I've already decided that the next time I buy tires, they'll be 35's. So what is the best ratio for the axles, 3.73, 4.10? Also, I have heard about the 10 bolt being a little on the weak side. In replacing the oil seals in the rear axle it occured to me that if the axle shaft broke, there would be nothing to prevent the broken shaft and wheel from just sliding right out of the axle. Is it worth my time and money to find some beefier axles? /forums/images/graemlins/ears.gif
     
  2. Derf00

    Derf00 1/2 ton status

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    Here is the best gear calculator I have seen, plug in the #'s and you can see what you need to do.
    Gear Calculator
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    Is it worth my time and money to find some beefier axles? /forums/images/graemlins/ears.gif

    [/ QUOTE ]

    yes
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    Either 4.10's or 3.73s with a diesel, 35's, and 700R4 would be about right. 4.56's and you get to many RPM. I think that 3.73's would be better for the RPM's if you want to cruise at 75 and need to kickdown.

    Harley
     
  5. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Yes 10 bolts are weak! You want 14BFF & D60 setup /forums/images/graemlins/peace.gif!
    Bill
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    FF14B suck w/ 35s if you plan on wheeling & a D60 is overkill w/ 35s. What are you plans for this truck? Give us your plans and we can give you a better answer.
     
  7. fbronson

    fbronson 1/2 ton status

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    Here's what I plan on in the forseeable future. Not too much more on the driveline besides the 35's, and the existing 4" lift. I would really like to get rid of the stock GM style steering drag link, and put on a link that is parallel to the axle, and connects to the passenger side knuckle. This will facilitate losing the sway bar as well. A rear disc brake conversion looks like it could be extremely useful as well. Other stuff will include bumpers, rollcage, winch, etc... Of course, as time and trails go by, I'll probably end up doing more /forums/images/graemlins/thumb.gif
     
  8. jakesdad

    jakesdad Registered Member

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    FYI, I'm running 4.10s in my 91 Sub with 35's and 408/4L60/10 bolts. The over-all gearing ends up being close to when it had 31's and 3.42 gears (stock). The speedo is almost dead on. If you tow, you might want the 4.56's. I'm considering the switch. Just my opinion.
     
  9. dodgedude99

    dodgedude99 1/2 ton status

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    something isnt working out right for me with that gear thing.
    when i pick the 700r4/241/4.10 combo its saying 4328 rpms at 66 mph with 40" tires.
    am i keying something in wrong?
     
  10. jakesdad

    jakesdad Registered Member

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    I got the same thing. Looks like you have to take the t-case low value out, then it works. You got the rpm at that speed in 4-Lo.
     
  11. fbronson

    fbronson 1/2 ton status

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    I just checked out the gear calculator. That is a really cool page! It does list the T-case high values even if you leave the low range in there, you just have to scroll down past 4th gear T-case low. How is towing with the 4.10's. Do you think that the extra weight of the 'burb makes a difference, i.e. would I be able to get away with pulling something up a hill with the 4.10's? Also, for anyone who has some experience, if I plan on some mild rock crawling, am I going to seriously risk breaking those 10 bolt axles? /forums/images/graemlins/ears.gif
     
  12. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    10Bs hold up ok to 35s if they are properly maintained. If I was starting over knowing what I know now I would have used a D60 in the rear. Or if i couldn't find one for a good price (which is unlikly because there are tons of them out there, more than the FF14B) I would have used a SF14B. I like the 60 better though because of the FF shafts. Another option (more expensive, though) would be the rear out of a late model F150, 9.75 R&P and IIRC disc brakes. D44/10B fronts do fine w/ 35s, keep good u-joints in the shafts and if you add a locker add better shafts as well.
     

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