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700r4 problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by skyrocco16v, Feb 5, 2004.

  1. skyrocco16v

    skyrocco16v Registered Member

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    hi all! i'm new here... so to start things off... i have an 86 k5 jimmy... bought for $500, needed an engine, and a tranny rebuild. i also am a technican at a chevy/cadillac dealer. i'm only 21, so i got help with the tranny rebuild.
    i bought a b&m tranny kit, ya know, the one with all of the seals, clutch fibers, clutch steels... ect. well, we got it together, and the 2-3 shift was very slippy.... especially under load. after about 200 miles it burned out the 3rd cluch due to a rolled lip seal.
    we rebuilt the clutch pack with the updated piston with the integrated seal, and now it's still doing the same thing but not as bad. i had one of the other techs road test it, and look at the books... ect...ect... and he seems to think that i could have put the wrong spring in the 3-4 accumulator. but he's not familiar with the b&m kit.... anybody out there have any ideas? i know that the accumulator spring is easy to change out.... but i'm just looking for other ideas... any?
    thanks,
    corey in NH
     
  2. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    was it the 3-4 clutch pack that burnt? or was it the forward clutch pack? most likely it was the 3-4 clutch pack and the correct parts were not used or installed incorrectly. that clutch pack you really need to watch waht you are doing cause one little mistake will kill the tranny. what manual are you using? i dont like the b&m 700r4 kits, seems like too many people are having problems with them.
     
  3. Blue85

    Blue85 Troll Premium Member

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    My personal opinion is that the B&M kit sets up your transmission to use the Corvette Servo and will not work correctly with a stock servo. If by "slippy" you mean the rpms flared up before third gear was fully engaged, then this is probably the culprit. I'm not sure exactly how, but their kit slows down engagement of the 3-4 clutch. Since the Corvette servo is bigger, it is slower along with having more holding force. That means the 2-4 band releases slower and eliminates the flare up in the 2-3 shift. The 2-3 shift is the most difficult one to get right in the 700, since it is the only one that uses crossover with one clucth disengaging while another one engages. The other shifts just get slightly earlier or later as the clutches speed up and slow down, since only one thing is releasing or engaging. With a crossover, you get binding if the timing is too tight and flare up if the timing is too loose.

    This worked for me, anyway. An accumulator spring won't solve flare up problems, it's just for fine tuning the firmness of that shift.
     
  4. skyrocco16v

    skyrocco16v Registered Member

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    yeah it is a flare on the 2-3 shift. i thnk the way that the kit changes the shift timing is that we left out the #4 checkball (i don't have my technicians guide to tell me what one that is...) and also we drilled an extra hole inthe valvebody for i believe it was the 2-3 shift valve. i had asked the tech that helped me with the rebuild and he seemed to think that if the 2-4 servo was sticking that it would cause a tie-up inthe tranny as oppesed to causing a flare. but i will keep the servo in mind. thank you for the help, if you can think of anything else let me know. thanks again.
    corey in nh
     
  5. Blue85

    Blue85 Troll Premium Member

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    Think about it. The 2-3 shift is releasing the 2-4 band while simultaneously applying the 3-4 clutch. The flare up happens because there is too much overlap. When the servo slows down (Corvette servo has more surface area, so more fluid has to move for the servo to engage or disengage), this reduces the overlap. Changing the servo is easier than trying to speed up the 3-4 clutch because you don't even have to open the tranny case.

    If the servo was sticking, that would probably cause binding, which could lead to a whole new world of hurt.

    Like I said before, I think the B&M kit is tuned for the larger servo, which is why a lot of people get the flare when reusing the stock servo.
     

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