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  1. BAD LUCK 79'

    BAD LUCK 79' 1/2 ton status

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    diff\'s

    Heres one most of you guys should know... i curently still have the original 3:73's in my 79' ... i finally made up my mind to keep a 350 in the truck.. what would still give me decent top end for the street.. and a good bit of torque for offroad..

    BAD LUCK is better than no luck at all!!!!
     
  2. Stoopalini

    Stoopalini 1/2 ton status

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    Re: diff\'s

    what size tires are you running? Any lift?

    The 3.73's will be fine if you are stock. The 350 really doesn't play a role in your gears; at least it wouldn't if I were making the decision.

    If you are building an off-road vehilce (lift, 35" tires, etc ...) then 4.10 or higher would be better.

    Thomas.

    -- '84 K5 Blazer --
    <a target="_blank" href=http://stoopalini.off-road.ws/blazer>My Blazer Site</a>
     
  3. txbartman

    txbartman 1/2 ton status

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    Re: diff\'s

    Tire size, axles and what kind of off-roading would help to make a good call. I had 3.73s with 31, 32, and 35" tires. With the 31 &amp; 32s, all was well. With the 35s, well, wouldn't pull teh bottom out of a wet paper bag (but would go over 100MPH!).

    Anyway, I went with 4.56s and have never been happier. 4.88s would have been too small of a pinion for 10-bolts axle. 4.10s would not have given me much of an improvement over the 3.73s.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  4. BAD LUCK 79'

    BAD LUCK 79' 1/2 ton status

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    Re: diff\'s

    i guess. i should have went into a bit more detail... must be all the bondo dust and primer.... well i've got what looks like 33's now.. but they use to be 35's.. new meats are to come in the near future...and they'll be 35's ... i'm sittin on an overall 6" suspension lift, but after reading the article on shackle flips i'm debating on keeping the blocks or not.. i'm not to much into rock crawlin,, just muddin and hill climbs... but that's for later...i've still gotta talk to travis "72 Travis" and see if he want's to sell his SM465 tranny and t-case set up .. i'm sick of automatics.. the rear end is a 12 bolt and the front a 10..

    BAD LUCK is better than no luck at all!!!!
    Is it bad that my truck is older than my wife?
     
  5. Stoopalini

    Stoopalini 1/2 ton status

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    Re: diff\'s

    with a 6" lift and 35" tires, your best bet would be to go with 4.10 or 4.56 gears. Those 3.73s would be ok with the 33" tires, but with 35s you should upgrade.

    I've got 33" tires, 4.10 gearing, and a TH350 tranni (3 speed) and I love it. Plenty of low end torque and jump off the line; but anything over 70 to 75mph really gets those RPMs up there.

    If you're going to go with a manual, or a 700R4, then the 4.56 gears would be best.

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  6. txbartman

    txbartman 1/2 ton status

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    Re: diff\'s

    I agree with Thomas... go with the 4.56s. I certainly wouldn't go any taller (4.88s) with a 12 bolt rear and 10-bolt front. The pinion starts to get too small to be considered reliable. Especially if you are flying through mud with lots of tire spin and they suddenly decide to grip something. You would probably grenade that pumpkin big time!

    Anyway, 4.56s will run you some high RPMs on the highway with 33s and especially with a manual or even an auto without OD. But that will begin to be alleviated by the bigger meats.

    My opinion, 4.56s. May suffer a little at highway speeds on gas, but you will get much better off-road performance than what you will see from 4.10s.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  7. BAD LUCK 79'

    BAD LUCK 79' 1/2 ton status

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    Re: diff\'s

    cool thanks for the info ya'll, so whats your opinions on the shackle flip???

    BAD LUCK is better than no luck at all!!!!
    Is it bad that my truck is older than my wife?
     
  8. BIGCHEVY

    BIGCHEVY Registered Member

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    Re: diff\'s

    I also have a 79 chev with 3.73's. if they are the original diffs they should be a 12 bolt in the back and a dana 44 in the front. i am running 38.5 inch gumbo mudders and i have lots of take off power. of course i have a 500+ hp 454. so that helps. i drove about 700 miles about a month ago with it and at 60 mph it was at about 2800 rpm. if i could have it my way i would put 4.10's in it for the extra grunt. :)

    IF IT AIN'T BROKE,YOU AIN'T TRYING HARD ENUFF
     
  9. BAD LUCK 79'

    BAD LUCK 79' 1/2 ton status

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    Re: diff\'s

    oh befor i forget to ask... what would be a good doner at the junkyard.. can't afford new stuff yet but i got some hookups at the junkyards around here... oh and i looked at my axels again in the daylight... it is a dana 44 in the front and 12 bolt in the back..... kinda hard to see with street lights at 2 in the morning...


    BAD LUCK is better than no luck at all!!!!
    Is it bad that my truck is older than my wife?<P ID="edit"><FONT class="small">Edited by BAD LUCK 79' on 10/10/01 10:08 AM.</FONT></P>
     
  10. Stoopalini

    Stoopalini 1/2 ton status

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    Re: diff\'s

    The shackle flip is a great way to lift the truck and still have good ride quality. The 1990 and up stock K5 springs have teflon pads in between the leafs, so the ride is much smoother with these. I've got a 2 1/2" shackle flip with 1990 rear springs, and it's smoother than before I lifted it.

    For you though, you would have to use a 4" shackle flip and then 2" lift springs (or blocks .. yuck!) to maintain your 6" lift; so it might be better for you just to keep the springs/blocks you have now until you get the diff/gear issue worked out.

    Look around for a 74-79 K20 3/4 ton 4x4 pickup, or even a 4x4 suburban. I believe these will be a direct bolt in, minus a few details (like e-brake cables)

    Too bad you weren't closer to TX, I read in the for sale board that someone close to Dallas has a 14 B FF for $100!

    Good luck,

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  11. MudFrog

    MudFrog 1/2 ton status

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    Re: diff\'s

    89 has teflon pads between the springs as well. And I was under the assumption they started that around 86ish? Probably wrong but I do know 89's have them as well.

    89 K5 Silverado
    <a target="_blank" href=http://mudfrog.rockcrawler.com>http://mudfrog.rockcrawler.com</a>
     
  12. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: diff\'s

    If you are planning on a manual tranny 4.10's would be much better overall with 35's, especially if you actually drive it on the freeway. The 4 speed allows a few more ponies to get to the ground and has a numerically lower first gear than the auto. I run 36" TSL's and 3.73's with a 4 speed and it's on the edge of needing a gear swap. 4.10's would be perfect for me, but i plan on larger later so I'll eventually go with 4.56's.

    4.56's and 35's would result in a cruise RPM of 3100 RPM...just so you know. 4.10's would put you at 2800, still a tad high but tolerable. Both these rpm's are at 70 MPH...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  13. DesertDueler

    DesertDueler 1/2 ton status

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    Re: diff\'s

    I am currently running 3.08s and 35s in the Jimmy. I have no problems with it. I can wheel up just about anything, and get great gas milage driving down the freeway. I have the extra low 1st gear of the 700r4 which helps take offs,and the extra 4 lo of the 208.

    86Jimmy 4"&35"MTRs,87 burb 4"&35"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     

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