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Ideal Setup for running 38's?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SAVAGE1, Aug 18, 2000.

  1. SAVAGE1

    SAVAGE1 1/2 ton status

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    Ideal Setup for running 38\'s?

    <font color=blue>What whould I need to do to my stock 85 to be able to run 38" tires. I don't plan on doing any hardcore rock crawling but I'm looking for a combo(gear ratios/ axle/ lift) that would be able to handle the tires. I need some input before I hit the bone yards. thanks</font color=blue>

    BLAZE IT UP!!!
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Ideal Setup for running 38\'s?

    This is the combo I think would work well for running 38's. 6" suspension lift, with 2" body lift (or 6" and some creative trimming). Gear ratio between 4.11 and 4.88 depending on what kind of tranny you have and what kind of wheelin you want to do. I would upgrade the axles as well. There are a few options here but I'm biased so I would say a FF 14 bolt rear and if you can afford it a D60 front ( a D44 front might live for a while, depends on how you drive it!) Better brakes would be next on the list here, a truck with 38's is not going to stop on a dime. Rear disks would be a good set-up.
    Just my 2 cents here, I'm sure there are a lot of different combos out there that work real well. [​IMG]
    Good luck!


    [​IMG]
     
  3. 84k5

    84k5 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    I would get at least 4.56, if not 4.88 gears. The FF 14 bolt is the best option for the rear, for the front I would say go with the Dana 60, even if you don't wheel hard. The stress of those big meats will break parts on a Dana 44 or 10 bolt. For the lift, it depends on what you want to do with it. If it was my truck, I would put a 6" lift on and cut the fenders, but if you're anti fender cutting you could use a body lift too. You could also use a suspension lift over 6", but most people will agree those don't ride very good, and offer little flex.

    Brian
    84k5, 4"Skyjacker lift,33x12.5 Goodyear MT/R, 15x10 Bajas
     
  4. riz

    riz 3/4 ton status

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    Re: Ideal Setup for running 38\'s?

    I agree with the 6" suspension and 2" body lifts.....although 4" suspension and 3" body would be fine too. I would go with the first combo since I don't much care for 3" body lifts. But that's a personal preference.

    L8r,

    .Riz.
     
  5. 4GUNZ4X4Z

    4GUNZ4X4Z 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    6"lift(fender trim),14corpff,dana60,4.11gears,203t-case(converted part time), and rear disc brake's(like said earlier)good idea. Hope you got a FAT wallet.
    just my .02. Remember if body lifts r not installed properly you might snap your distributer.

    <font color=blue>Professional <font color=red>JEEP EATER</font color=red>, it's a population control thing</font color=blue>[​IMG]
     
  6. Scoobydoo

    Scoobydoo 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    NO WAY 4.11 with 38"s ! Minimum 4.56's
    Ideal is the word you used, so I say 4.88's everything else sounds right! especially that wallet part[​IMG]
    by the way the D60 and the 14boltFF are probably the ONLY things you may find in the boneyard!
     
  7. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Re: Ideal Setup for running 38\'s?

    Well, since I plan on 38's in the future, here is what I am going to do:

    Big time fender cutting.
    Front: 5" suspension lift (4" springs in the front with 2" longer than stock front shackle neting 1" of lift, I have these on the shelf here at the ColoradoK5.com mega shop).
    1980 F250 front shock towers.
    Rear: 4" ORD flip (it sits higher in the rear with the top off, I will see if it is level after the front shackle install) and flip the overload.
    Dana 60 4:88 gears, ARB locker
    Full-float 14-bolt with 4:88 thick gears, Detroit locker, TSM disk brake kit.
    4L80E overdrive with manuel valve body.
    NP205 (maybe the NP241 with 4 to 1 kit and fixed yoke, not sure yet).

    If you are not a big wheeler you might get away with beefed up Dana 44/12 bolt, 6" susp lift, trimming. Also, I am not a big fan of large lifts just to clear big tires.


    [​IMG]
    5,000 Pounds of American Rolling Steel
     
  8. titanic

    titanic 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    Hey Steve,If you plan on having a total lift of 6", a D60 will raise the front end up more than the stock axle-6" lift will be more like a 7-8"
     
  9. laketex

    laketex 3/4 ton status

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    Re: Ideal Setup for running 38\'s?

    Here's what I did to mine, and my next set of tires will be 38" swampers or 37" boggers.

    14 bolt FF rear, 4.11 gears, detroit, new bearings/seals/brakes
    D44 front, 4.11 gears, open, new bearings/seals/brakes/u joints
    Rebuilt TH350 tranny/ hardened sprag/ shift kit
    Stock NP203, still fulltime
    4" tuff country front springs, actually net 5.5" new
    4" custom shackle flip rear (truck actually sits level though)
    some major fender cutting, when I actually go to 38's, I'm fully prepared to hack as much as nessessary, even if it requires custom inner fenders

    What is next on the list:
    383 engine
    doubler case
    then a D60 if the 44 becomes a breakage problem. haven't decided on a front locker.

    I do admit that 4.11 gears are a tad high for my tires but they came stock and I didn't want to fork an extra 600 bucks for a new gearset. I'd actually love 5.13, but this truck won't see much street time at all.

    Just my .02

    [​IMG][​IMG]
    Durant, Ok
    '79 Blazer in progress
     
  10. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Re: Ideal Setup for running 38\'s?

    Thanks Steve, I know the 60 has higher perches, I will measure Shawns to see the diff between the 60 and 44, I just installed the ORD flip yesterday and it raised the rear another 1/4" and it sat a little high in the back to begin with. I have 4" springs in the front and will be trying out a 1" (2" longer than stock) height front/rear shackle so if I get more height from the 60 perches I could be looking at almost 6" of lift in the front with only 4" springs, not bad at all. I think my 14 bolt perches are a little higher that the 10 bolt, that might be why it sits up higher in the back, that and my top is off - for good.

    [​IMG]
    5,000 Pounds of American Rolling Steel
     
  11. ggallin13

    ggallin13 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    I would lift no higher than 6", and I would avoid a body lift (I personally don't like them, I have seen some freaky breakage on other trucks). Just trim the fenders as needed! You won't have to trim as much as you think, if you are not going to crawl over big rocks.

    I would go with at least 4.88s, since you said you aren't going to crawl too much you shouldn't need anything lower. I would get rid of you 10-bolts ASAP. I ran 35s with a 10-bolt rear for about three weeks cringing the entire time, waiting for that horrible CRACK! sound.

    [​IMG]
     
  12. dpearson

    dpearson Registered Member

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    Re: Ideal Setup for running 38\'s?

    Hey Steve,

    Have you already bought the tranny for the 4l80 manual valve body dropin and how much is the whole thing going to cost? I'm sure you will be posting the results, cant wait!!
     
  13. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Re: Ideal Setup for running 38\'s?

    Nope, just in "looking at my options mode"

    [​IMG]
    5,000 Pounds of American Rolling Steel
     
  14. SAVAGE1

    SAVAGE1 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    Thanks guys. Looks like Running 38's will give me more trouble than I can afford. I just found a killer deal on some Swampers and wanted to get an idea of the work I have to do before I can actually install them. I'll probably just get the tires anyway and see what I can do from there. Preferebly the biggest I'd run would be 35's. Ahhh... too many choices!!!

    BLAZE IT UP!!!
     
  15. ken

    ken 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    I really believe that running large tires and the accompanying low gears is too hard on the overdrive of an OD auto tranny. Even the 4L80E will probably not be able to handle the constant stresses placed on it by pushing a brick wall of a truck down the interstate at 65 MPH with low gears and wide, tall tires. Those tires take lots of HP to turn. When the tranny is in OD, the input turns slower than the output, thus as long as you have enough HP to "grunt" the slow input speeds, the tranny takes this up to produce a higher output speed. In other words, the tranny takes most of the abuse. Maybe a 4L80E will last, maybe not, but I'm not willing to spend $2,000+ to find out…my TH400 works just fine! And, do you really expect to get that much better gas mileage to warrant the expense of a 4L80E?? That $2,000+ will buy a lot of gas!! It'd take you close to 100,000 miles to pay for the difference!!

    What I've done to my '77 Sub:

    Dana 60, 4.56 Powr-Lok (tight clutches)
    14 bolt rear, 4.56 Detroit
    454, mild RV build, ported, polished, balanced, etc,
    TH400 trans, shift kit, deep pan
    NP 203 with Doug Nash shaft conversion (may do the Doubler thing)
    12" National spring packs, SOFT ride, EXTREME flex!
    Rancho RS9012s, set on '2'
    ORD front shackles with 9/16" spring bolts
    39.5" Swampers, 12" Weld Racing wheels


    ken
     
  16. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Re: Ideal Setup for running 38\'s?

    Ken, good point on the overdrive, how is your RPM range going down the highway with the 400?

    [​IMG]
    5,000 Pounds of American Rolling Steel
     
  17. ken

    ken 1/2 ton status

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    Re: Ideal Setup for running 38\'s?

    Well, since my factory tach isn't hooked up yet, I would guesstimate about 23-2400 at 65 MPH, remember the 39.5" tires aren't but about 38" or so! I get 10 MPG, not too bad for a 454 with 39" tires, and 12" lift! I figure if I put in a 4L80E I might get 12 MPG, all the while worried that I'll have to rebuild it long before the TH400!!!!

    ken
     

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