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Overdrive

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tecton, Feb 26, 2003.

  1. tecton

    tecton 1/2 ton status

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    ok...im stupid when it comes to trucks...ive only had my liscense for a year in june...and im ignorant. But i want to learn and ive learned alot from here. So here is my attempt to learn some more.

    I had a 83 chevy scottsdale that didnt have overdrive...thing had D-3-2-1....my 86 k5 has OD-d-2-1...someone explain the difference....should i drive in D and use overdrive only on highways? is one better on gas? help here.
     
  2. BlazinRojo

    BlazinRojo 1/2 ton status

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    Yes, both trannies are overdrive. I'm pretty sure the 4th gear (someone back me up on this) regardless of what your dash says, is an overdrive gear with a ratio <1:1. Your '3' on your Scottsdale should be your drive gear (1:1), as well as the 'D' on your 86. My '83 K5 has an overdrive tranny, and I'm 99% sure the dash just says 'D'.

    I always drive in overdrive, never had problems with gear hunting that some people talk about. I got a long life out of my last tranny (130K+ with one crummy rebuild) driving in OD unless towing or on a steep grade. Driving around town, my tranny never gets above 170 degrees, drops to 145 when its at high speed (i.e. in the actual overdrive gear, not just the selector position) due to the torque convertor lockup in a 700r4. And the stock tranny was still going strong after 130K, but wanted a new one that I was sure could handle the new engine's power.
     
  3. nevercomplete

    nevercomplete 1/2 ton status

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    Your sure the '83 didn't have overdrive? My '83 does, if it had 4 gears it does. It would have been a 700R4, which would be the same tranny as the '86. Basically overdrive is just an extra gear. It lets your engine run at lower RPM's. It's my opinion you should only run your truck in overdrive if your going at a constant speed like on the highway. Driving around town in overdrive just causes your tranny to shift more, and that causes wear and heat. Hope this helps. So your in Beckley, I am too, home on leave till the 5th. Where exactly are you?

    Jon
     
  4. tecton

    tecton 1/2 ton status

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    im about 3 miles north of beckley near bradley

    truck had 700r tranny...thing is tho...in my truck, i could never get past 65mph....and in the blazer ive come home on the interstate pushing 80 (spedometer goes to 85)

    whats this about leave it out of OD to go up hills and stuff
     
  5. nevercomplete

    nevercomplete 1/2 ton status

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    Sounds like your '83 had a 305, I had an '85 with a 305 and it wouldn't do much over 65mph. The tranny shouldn't have anything to do with speed, most likely it was lack of engine power or rear end gearing. Your truck should automatically downshift going up hills, if it keeps "searching" for gears I put mine in 3rd. Other than that I leave my truck in Overdrive on the highway.

    Jon
     
  6. bee32

    bee32 1/2 ton status

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    [ QUOTE ]
    whats this about leave it out of OD to go up hills and stuff

    [/ QUOTE ]

    Going up hill you tranny will downshift to try and keep up the speed to stay in OD. It can shift alot (up and down) causing alot of wear and tear. When ever your are going up hills or towing just leave it in 3rd gear. Saves the tranny. And keeps it cool. As far as you only going 65, what gear ratio is in your rear diff? Sometimes that can factor into your top end speed.
     
  7. tecton

    tecton 1/2 ton status

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    tell me how i can determine it and ill tell you
     
  8. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    ok...im stupid when it comes to trucks...ive only had my liscense for a year in june...and im ignorant. But i want to learn and ive learned alot from here. So here is my attempt to learn some more.

    I had a 83 chevy scottsdale that didnt have overdrive...thing had D-3-2-1....my 86 k5 has OD-d-2-1...someone explain the difference....should i drive in D and use overdrive only on highways? is one better on gas? help here.

    [/ QUOTE ]

    OK you got some good answers, but just to clear something up.
    In 81 or 82 when GM introduced the 700R4 which is an overdrive tranny with 3 being a 1:1 and the D being the actual overdrive at 0.67:1 I am not sure about the axact ratio but I believe that is it, they didn't mark it on the shifter as OD.
    in later years they started this OD, D, 2, 1.
    So if you have an auto with 4 gears it's an overdrive.
     
  9. BlazinRojo

    BlazinRojo 1/2 ton status

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    On my 83, on my fender, where the jack sits under the hood (or possibly on the drivers side fender) was the 'Service Parts Identification" sticker, that listed all the options my truck had (paint, A/C, tires....etc) On my sticker it lists my rear axle as one of the options, something like '3.08 rear axle'. Hopefully that will tell you your rear end ratio (i.e. 3.08:1 for me)
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Close! 700R4 OD ratio is .70, the 200-4R is .67 /forums/images/graemlins/smile.gif
     
  11. imiceman44

    imiceman44 1 ton status

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    Well I knew I was close, I have the 200-4R in my Olds, and the 700R4 in my Van, so I confuse them.
     

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