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crawl ratio

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TX Mudder, Sep 14, 2000.

  1. TX Mudder

    TX Mudder 1/2 ton status

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    I have the 205/265 combo with 3.73 axles. If the tcase is 1.96:1 and the stick is 6.55:1, then my overall crawl ratio is aprox 48:1, right?
    When I actually put it this low (granny low and 4-lo) and you step on the gas, you can rev it to red and you are still going creepy crawling slow. I can understand why this is good in certain situations.
    Now the question. Why in the world would you want to increase the crawl ratio anymore? I have seen guys go to 100:1. Why? Even on rocks (which I don't have where I go wheeling) I don't see why you would need any more gear reduction. Even in the mud where you want wheel speed, 50:1 is usually overkill for gear reduction.
    Why would someone want to install the ORD 203/205 doubler? isn;t 50:1 good enough?
    I don't get it...
    -- Mike
     
  2. Andreas

    Andreas 1/2 ton status

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    The guys using 100:1 are probably rollin´ on 40" tires and up. Just a guess.[​IMG]

    Andreas

    406cui of pure sh*t[​IMG]
     
  3. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    Here is a TOTAL guess why some one would like REAL LOW gears. When they are going down a STEP down grade they do not have to uses their brakes at all. They uses all motor and gears to walk down the surface. This way they dont have to thing about the brakes going out, or them getting hot. If that is not right, I would like to know why someone wants REAL LOW gears as well. My other thought is if your pulling a 100 foot boat out of the water that has 4 502's and you dont want to by a tractor, to move boats around that might work as well.
     
  4. BigBurban

    BigBurban 1/2 ton status

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    You wanna see a silly crawl ratio? See if you can make out what's on this Toyota's hood...

    http://www.off-road.com/rock/vernal2000/gallery/event/DSC_0055.jpg.html

    Yes, that's 195:1... It's crazy to ride in. Redlined in second is like 3mph with 35s if I recall. He can let off the gas and the thing will climb most rocks at idle... A stock four cylinder idle at that. He runs a stock Toyota transfer case in conjuntion with a Marlin Crawler unit. To give you an idea of how low this gear is, he used 2nd and 3rd on most "slow" obstacles in Farmington.

    <font color=blue>~BigBurban</font color=blue>
    http://www.geocities.com/crash607
     
  5. 6.2Blazer

    6.2Blazer 1/2 ton status

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    In really severe rocky terrain, the low gears help maintain vehicle control as you don't need as much throttle (which equals speed) to overcome obstacles. With a higher crawl ratio (50:1), there could be times when, let's say, half throttle is needed in order for the engine to make enough power to climb a large rock....the more throttle the higher the rpm and therefore the faster the vehicle is moving. If you had 100:1 ratio you could probably idle over the same obstacle and have more control and less chance of breaking parts. To get an idea of how this works, keep your truck in 4-hi and try go over some tough obstacles, I bet you have to slip the clutch a lot and it makes it difficult to climb over stuff smoothly. The difference between your 4-hi and 4-lo in making it easy to climb over stuff is about the same as comparing the 50:1 to the 100:1.
    Now, I still think 100:1 is overkill in most circumstances and is really only needed in really rocky trails.
     
  6. laketex

    laketex 3/4 ton status

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    Actually they say marlin himself has something like a 1000:1 in his personal rig, the thing has 3 transfer cases. Most say that's too extreme. But I'd say I want low gears for decending ultra steep hills, generating more torque to the ground, crawling because I want a standard but don't want my foot on the clutch all the time. I want to run a more dependable low hp engine and make up the power loss through use of gears.

    I saw a 14:1 tranny/tcase combo that is all built into one 20" case for sale on the pirate 4x4 board. For ONLY[​IMG] 2000 bones. It is designed to go after a regular transmission to create extreme low gears. My mind started wandering...I wonder how many parts I could break with that thing, a 4 speed tranny, and 5.13s....a 470:1 crawl ratio...ouch!!!!

    Bryan

    [​IMG][​IMG]
    Durant, Ok
    '79 Blaze- 350/350/203, 14B w/detroit, D44, 4.11s, 4" susp, 36" TSL
     
  7. realsquash

    realsquash 1/2 ton status

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  8. realsquash

    realsquash 1/2 ton status

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    I ahve 35's, and a built 454. I idle over most terrain in 2nd gear lo-lo. When i really wanna, i shift into granny low, lo-lo. 102:1 crawl is way too slow for most things. But i like to try it as slow as possible first.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  9. Steve_87K5

    Steve_87K5 1/2 ton status

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    My 87 is 60:1 with 35s (NV4500+205+4:88s). I use the lowest crawl when backing loaded heavy trailer over curbs and such. Saves the clutch.

    SteveB
     
  10. Brady

    Brady 1/2 ton status

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    Realsquash did you use the auto 205 for this?I have the 465 and 205 and want to put a doubler in.I have 3 203's sitting here waiting but I need an auto 205 to keep the length down.Also did you use a CV joint in the rear?Brady
     
  11. titanic

    titanic 1/2 ton status

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    I've got the Doubler and really only got it to improve front drive shaft angle. After I started using the 132:1 LO-LO gear, I realized I could climb large rock steps without having to use the throttle at all or worry about stalling out on a step hill.
     
  12. DBLAZER

    DBLAZER 1/2 ton status

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    I have the 700r4 3.8 to 1 first gear. The atlasII tcase with a 3.8 to one low range. 5.13 gears. 38" swampers.
    Why do i want to be so low. I wheeled the truck before and after. It is AMAZING the control i have over the truck. Where alot of people have to throtle over obstacles I finesse. In the mud or snow or sand, I can see where it would hinder you. But with what I do, play on the rocks, the gears are the only way to go. There is no substitute. When you can finess over an obstacle it is much better on your ride, your axels your gears, your drivelines etc etc then flooring it and just bouncing over. Slam bam . Just my .02 By the way, with my setup who can tell me my final ratio????? How do you figure it out DUH.[​IMG]

    [​IMG]
     
  13. blazer72

    blazer72 1/2 ton status

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    It all been said but I can shiftup a few gears if the 102 or so to 1 gets to slow But it shure is nice to never stall or to never have to bounce over something and trust me at 6200 lbs tha bounceing get costly!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  14. DBLAZER

    DBLAZER 1/2 ton status

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    My sentiments exactly

    [​IMG]
     
  15. titanic

    titanic 1/2 ton status

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    I'd say around 160:1 if you count the torque converter as another 2:1
     
  16. blazer72

    blazer72 1/2 ton status

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    I run a NV4500 so it 102 to 1 plus the tires which will change do to load or there air setting. I have walk around over, though thing in a controled way get past in one try that other had to take runs at. I can also almost always match the power curve to the climb!!!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  17. realsquash

    realsquash 1/2 ton status

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    Nope, I used the manual-tranny 205 and adaptor. I also used the manual-tranny 203 and adaptor. I didn't use a CV joint in the rear, but my truck is a long-box pickup. With my combination in a blazer a CV in the rear is almost required (it's required IMHO).

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  18. drivelineman

    drivelineman 1/2 ton status

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