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O/T, auto transmission specialist question?

Discussion in 'Uncategorized Threads' started by K-GUNS, Sep 3, 2008.

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  1. K-GUNS

    K-GUNS Member

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    We have power stroke diesels at work and when hauling heavy loads you switch to tow/haul and shift patterns change,when braking down hill the trans downshifts to hold you back. Exactly like you say you want to do with your vehicle ? Ford makes their trucks do this with diesel engine/auto trans.
     
  2. k1200ltc509

    k1200ltc509 Member

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    The Chevy 2500 diesels work the same way in tow mode. The trans downshifts to help with braking.
     
  3. maclellan1911

    maclellan1911 TS Member

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    auto will shift itself, if you are on a really steap grade you may shift into lower gear manually. most part, if you are at a reasonable speed the trans will shift to where it needs to be
     
  4. ou.3200

    ou.3200 Well-Known Member

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    I think that it is fine to lock out the overdrive on a passenger car when going down hill. You can use the lower gears but I was told by a mechanic that brakes are cheaper than transmissions. He was not in favor of gearing down in a passenger car.
     
  5. over the hill

    over the hill Active Member

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    Passenger cars these days have few if any of HD parts.

    Transmissions are light duty at best. At 1800. to 3000. for a overhaul or a new one Id be cautious if I were you.


    Regards...Gerald
     
  6. hoggy

    hoggy TS Member

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    GM's 460E transmission has a brass planetary/ring gear that can wear very quickly if you downshift and use 2nd gear for braking. I know because I destroyed this the ring in my Trans Am. You do not want to do this as all the brass particles get everywhere. The torque converter needs to be replaced because there's now way to flush out all the brass particles. This was a 1995 so maybe they changed it in later years. Also I do not know about other auto tranny's. All have a tendency to over heat if used too much for braking. I suggest you get an axillary tranny cooler. It will help.
     
  7. yenko

    yenko TS Member

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    Jan 29, 1998
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    use your brakes,less expensive.what year vehicle?what trans?model.
     
  8. Husky44

    Husky44 Active Member

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    Location:
    Calif/Idaho
    Hydraulic pressure is used to apply the clutches the hold the sun or planetary gears firmly for the ratio required for load-speed. The torque converter drives the pump that supplies pressure, when coasting the pump now drives the torque converter and may cause a reduced pressure, clutch slippage, and heat which will decrease the life of the transmission. Just simple answers for a light duty transmission, modern diesel transmissions were engineered for engine braking.
     
  9. Quack Shot

    Quack Shot Active Member

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    A lot depends on the design of the transmission and what gear you downshift into. If you go from overdrive into direct 1:1 ratio with the planetaries locked, you may actually decrease wear. Same goes for some 5 or 6 speed manuals. The 1:1 ratio usually means less gearing, thus less wear. Lower RPM usually means less pump pressure, so that can actually cause slippage and overheating.
     
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