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35's + 4.10's + '91 K5?

Discussion in 'The Garage' started by southernspeed, Jan 4, 2006.

  1. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    When I put these 35's on my '78 with 3.?? gears the speedo was expectedly way off. When I put 4.10's on there the speedo was just about spot on.
    I'm now putting the 4.10 axles with the 35's on my TBI'd '91.
    My question is, will I need to mess with my DRAC (been reading up on them) or will my ECU just see the 'normal' input because the gears are turning everything at a fairly normal rate??. I'm thinking of speedo accuracy, trans function and RWAL function.
    Has any one got this combo on a '89 to '91 with 700r4 and 241? Did you have to mess about with DRAC?
    Thanks, Mark.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    If lockup is controlled via vehicle speed (makes sense, just never studied it) then your TCC will be messed up along with your speedometer. I have no idea if having wrong speed input will really hurt regarding VSS and the idle input it has.

    DRAC is easy to play with, you won't have a problem getting it right. :)
     
  3. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    That's easy for you to say 'oh knowledgeable one'!:D
    Think I'll run it as is and see, then mess with the drac if need be!
    Thanks.
     
  4. cbbr

    cbbr 1 ton status GMOTM Winner

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    Close - 4.10's, 35's and a th400. the 35'5 threw the speedo off by a few mph, but not many (about 5 at highway speeds) and have not really affected anything else that I have noticed except for dropping hwy RPM's a little.
     
  5. ProJunkRacing

    ProJunkRacing 1/2 ton status

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    look around ask lrazer he has that same combo with 4.56's no problems with his trans as far i asi know
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, if you can stand the speedo being off a bit, and it's that close, it probably won't make a difference for you as others have experienced.

    I use my trip odometer all the time, so it helps to figure actual gas mileage to have the speedo read right.

    It really is simple. Here's a post if you end up needing the info: http://coloradok5.com/forums/showthread.php?t=124012&highlight=drac :)
     
  7. Chaddy

    Chaddy 1/2 ton status GMOTM Winner

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    I have that same combo....90 blaze, 700, 241, 4:10's, and 35's.....my speedometer reads 5 mph over at all times.
     
  8. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Does the trans shift ok & at the right times? Cruise work? RAWL seem ok?
    Thanks,
     
  9. Chaddy

    Chaddy 1/2 ton status GMOTM Winner

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    everything has been perfect for around 5 years now
     
  10. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Cool thanks!
     
  11. wayne

    wayne 3/4 ton status

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    I would skip 4:10's unless you already have them. 4:56's seemed to work a lot better for me when I had my 89 Jimmy set up with 35's and 4:56's. I was actually getting better gas milage around town because it didn't have to work near as hard. I never checked exact numbers but I know it took less gas to make the same trip from stock to modified. My speedo was also pretty close to being correct too, it was only off by about 2mph.
     
  12. ProJunkRacing

    ProJunkRacing 1/2 ton status

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    yeah my friends is close too
     

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