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Compression Braking?

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

  1. Rockjunkies

    Rockjunkies 1/2 ton status

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    How much compression braking will I get with 38"s a sm465 and 4.11 gears? It will be behind a stock 350.

    Keep it simple <a target="_blank" href=http://coloradok5.com/gallery/album71>http://coloradok5.com/gallery/album71</a>
     
  2. Triaged

    Triaged 1/2 ton status

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    More than my auto trany and 3.73 gears will. I don't understand what kinda answer you are looking for. Maybe you should try to get a ride in someone that has about the same combo.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  3. 86K5TrailBlazer

    86K5TrailBlazer 1/2 ton status

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    you wil get 43.39 on the CBI but that depends on whether you have any blinker fluid or not . .


    but really what Dan said [​IMG]
     
  4. zakk

    zakk 1/2 ton status

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    and only run chrome muffler bearings. that is what i run [​IMG]

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  5. RedDwarf

    RedDwarf 1/2 ton status

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    Depends what gear you're in.
     
  6. chevidog

    chevidog Registered Member

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    I haven't personally ever broken any of my compressions, but I have seen it happen- not pretty. Are you still running stock compressions or are you utilizing high-perf. aftermarket compressions? With those 38s I would certainly be worried about compression braking too. Just feel her out, but don't push too hard, and see what happens.

    couldn't help it :)

    If you have a good crawl ratio, you should be fine. Think of how fast you can go in first-low and that should tell you about your CB capability- of course i'm assuming the question was pertaining to offroading and not highway.

    crawl ratio is calculated by multiplying axle ratio by tranny ratio by transfercase ratio. A decent/good offroad ratio starts around 50:1 or so, and the higher the better. Also, the larger the tire, the poorer the CB-just like higher gearing (numerically lower).
     
  7. hammer

    hammer 1/2 ton status

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    ? I beleave they are talking about engine braking meaning you let off the gas and the truck slows down also called brake horse power "bhp" my camaro has a lot of bhp on a long high going down it in overdrive I have to step on the gas cuz the car will just shut down from all the horse power and high comression
     
  8. 90K5

    90K5 1/2 ton status

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    I think I know what you are talking about. Engine braking? When you take your foot off on the highway, and the engien revs up because the wheels are turning too fast? I get a lot of that with my 4.11's and 33's, so you will have less with 38's

    90K5
     
  9. chevidog

    chevidog Registered Member

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    Yeah, I wasn't very clear. CB is the force created by the drivetrain that resists the vehicles motion. CB acts like a brake when the vehicle is travelling faster than the drivetrain, according to the engine rpm. I still assume that the question was pertaining to off road, though. So the top speed in (1st, low range) gear is approx. how slow the setup will allow you to go when used as a brake. The lower the gearing (crawl ratio) the better the compression braking, whether automatic or manual. Manuals, of course, will give better CB since the engine rpm is always linked to the ground - not cut out by the torque converter as in an automatic. I hope this clears things up a bit. Or let me know if someone slipped me some acid and forgot to tell me.
    caleb
     
  10. Rockjunkies

    Rockjunkies 1/2 ton status

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    Yeah, that's what I am talking about. But anybody have experience with a simillar settup. I do alot of hill climbs and decent's, and want to know what to expect when I put the 38's on. Trying to talk my self out of a doubler or gear change, but looks like I will be heading in one of those directions.

    Keep it simple <a target="_blank" href=http://coloradok5.com/gallery/album71>http://coloradok5.com/gallery/album71</a>
     

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