Thinking about a 700R4 or maybe the 200R4

Discussion in 'Transmission & Driveline Topics' started by rocket dawg, Nov 19, 2015.

  1. rocket dawg

    rocket dawg Veteran Member

    154
    1
    May 5, 2015
    Grand Rapids Mi
    Last winter I broke my ankle so all projects were put on hold. This spring the car will get worked on. I still dont know which trans to get. This a 2nd gen car, Holley 750 but someday maybe Fuel injected. With the 700 being geared lower, does that slow the car down compared to the 350 or 200R4 off the line? Or spin the tires more? I seem to be running high RPM's even cruising at 60 mph, like 3200 >>Maybe it was my torque converter choice? This year the speed limit will be raised to 75 MPH on the highway, I really dont want it singing along a 4 grand all day long. MPG will hit an all time low.
     
  2. black_aerocoupe

    black_aerocoupe Veteran Member

    The more stable engine power is, the more easily it will absorb a larger shift percentage drop. This is a reason GM revamped the 700-R4 for the 1990s and made it electronic; it is a good match for the stronger EFI engines. Even with similar power number, an EFI engine tends to have more stable, precise fueling, and not fall out of powerband as much as a carb.

    I always preferred the 200-4R with a Q-jet, however. And a lot of softening of shift characteristics is accomplished with a higher stall converter.

    And those are my opinions. Some guys like having an engine in its' powerband all the time, hate having to downshift, and feel 4.10 gears are great. I prefer a low rpm cruise and overdrive, and mileage.

    Either way, a lockup converter can be a win- win.
     
  3. dailycruiser81

    dailycruiser81 Member

    42
    3
    May 19, 2013
    ft lauderdale
    I'm running a 2004r from monster transmission that was a very nice swap over. It is in an 81. Any questions hit me up
     
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  4. rocket dawg

    rocket dawg Veteran Member

    154
    1
    May 5, 2015
    Grand Rapids Mi
    Thanks, I will when it get closer.
     
  5. dailycruiser81

    dailycruiser81 Member

    42
    3
    May 19, 2013
    ft lauderdale
    Both shift different.
     
  6. bigdav160

    bigdav160 Veteran Member

    591
    3
    Jan 11, 2006
    Klein Texas
    Personally, I would go 700R4. I rebuilt plenty of 200-4R's back in the '80's. And that was with low power 307 Oldsmobile engines in front of them. Yes, the Grand Nationals got an enhanced version so with enough money you can build one that puts up with 400hp.

    The 700R4 are more plentiful and cheaper to build. I know some people don't like the gear ratios.
    Driveshafts are relatively cheap and easy to shorten. My 2cents
     
  7. smace

    smace Veteran Member Lifetime Gold Member

    387
    8
    Aug 17, 2008
    Ocala, Florida
    What kind of gas millage can somone expect going from a 350 to a 200-4r on a stock 350. I currently get 12.8 mpg in my stock 79. Is it even worth doing it for hwy driving?
     
  8. Gary S

    Gary S Administrator Lifetime Gold Member

    19,909
    29
    Apr 14, 1999
    Bismarck, North Dakota
    In theory, the .67 overdrive of the 200R4 should improve the mileage by that percentage. However, there are a lot of other factors that come into play. The 200R4 has a lockup torque converter so the mileage improvement on the highway should be more than the .67. So, make a guess. Would that .67 drop to .60 percentage of fuel comsumption, or would it drop even more? Again, other factors come into play. At what rpm is the engine running now at the speed you expect to drive, and at what rpm will it be running with overdrive? And, at which of those rpms is your engine more efficient?
    Taking a guess number at .60, you could expect to use 60% of the fuel you are using without overdrive. Using that "guess", you should get around 20-21 with overdrive. At 21mpg, you would burn 48 gallons of gas per 1000 miles driven on the highway. At 12.8mpg you burn 78 gallons of gas. The 30 additional gallons of gas at $2.50 a gallon cost you an additional $75 per 1000 miles driven. If you spend $2000 converting the car to overdrive, you should get your investment back in 27,000 miles. Again, that is all theoretical and many factors come into play. What will gas cost by the time you get 27,000 miles driven? Will the tranny need to downshift on the highway if you encounter hills or traffic?
    We can play the "what if" game forever and never come up with accurate numbers. The only way to get the real world numbers is to put in the tranny and drive the car.
     
  9. jthomas

    jthomas Veteran Member Lifetime Gold Member

    1,300
    21
    Dec 5, 2007
    NorthCentral PA
    Here is a real world example of what Gary described. I have 3:73 gears and 26.8" rear tires. Engine is a mild 350 (360 hp). I was getting 11.8 mpg average on the highway with a TH350. I swapped in a TH200-4R with lockup converter (same 3:73 rear gears and same tires) and now I get 20.1 mpg average on the highway. When I travel long distances I use just over half as much gas.
     
  10. ssupercoolss

    ssupercoolss Member

    85
    0
    Nov 3, 2015
    PA
    Wow....thats some good MPG. I'm jealous. i'm 330hp, 3.42, 200-4r and 15 mpg highway.
     

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