1. DentalDart

    DentalDart Well-Known Member

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    I fought with my KD and throttle cable for a while due to a flare up between 2nd-3rd shift.

    Replaced TC and adjuated throttle cable and KD cable. I have no flare ups. Shifts are crisp but high mph compared to stock. I believe I have the correct speedo gear, its yellow... I counted the teeth before but it was a while ago.

    Per google... stock 1st-2nd shift should be around 18mph and 2nd-3rd should be around 28mph. When I get my shifts around those speeds the 2nd-3rd has a flare up.

    My 1st-2nd shift is at 22ish mph and 2nd-3rd is at 44mph. Tight 3500-3800ish stall TC (its a good TC one from GTX John). Cheetah vb and shift kit. Double wrap front band, 904 transmission rebuilt (Tony helped me rebuild it). 5.0 lever and 2.74 low first gear ratio (I think thats what it is called) 3.23 gears, sure grip rear end.

    Do my shift speeds need to be brought down? I believe there is a governor in the tailshaft of the transmission? Is this what can be changed to bring the 2nd-3rd shift speeds down? Or
     
  2. oldkimmer

    oldkimmer FABO Gold Member FABO Gold Member

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    Adjust the kd cable some more. Also it can be the way your valve body is set up. Kim
     
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    • AJ/FormS

      AJ/FormS 68 Formua-S fastback clone 367/A833/GVod/3.55s FABO Gold Member

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      yur in trouble.
      The Speed-O gear has NOTHING to do with the upshift speeds; it's one and only job is translate driveshaft rpm to mph for your Speed-O.
      The governor only works in auto shift mode.
      Since yours is still working; It commands all shifts when "Drive " is selected.
      When you manually select Second or First, the governor is told to buzz off.... more or less.

      While the governor is on line
      , ( in auto-shift mode)
      The Line-pressure plus the Throttle pressure, together, oppose the governor, to delay the upshifts, by increasing their combined pressure. They combine to become ONE. Your throttle position controls the throttle pressure, but line pressure is set before the pan goes on.
      NONE of these have anything to do with flare ups, unless grossly maladjusted.
      Flares are caused by the inability of the clutches or bands to progressively lock up; or by the shift control valves waffling around the shift pressure, or sticking valves, or a screaming internal pressure leak.
      Sometimes the Second gear band needs adjustment, because it is outside of the working range of the servo. Sometimes the 2-3 flares because the Hi-drum is too slow to engage or the clutches are worn out, or the oil is too slippery.
      With your foot-feeder fixed, both shifts should occur at about the same engine rpm. These shifts are controlled by the spring calibration of the shift valves, as they oppose the governor. If one shift occurs considerably later (especially if it is the 1-2,lol) , this is very annoying.
      The BAD NEWS is this, shift flares are almost always gonna need a tear-down.
      You may be able to crank up the LINE- Pressure to overcome some of the flare, but the trans will shift harder in the process. You may be able to adjust the throttle-pressure to overcome some of the flare, but the other shift will become harsher.
      IMO, a pressure test per the service manual may point you in the right direction, but the results will be directly meaningful only with the experience of the guy doing the test.

      That's a personal preference;
      as for me;
      I like to be in top gear by 30 mph, under "normal" acceleration, but at more throttle, a 4000rpm shift is ok. But it has to downshift by itself at Part Throttle to pass at 55/60 mph.
      I do NOT like the trans to be hunting for a shift, while in traffic. And I especially don't like a screaming engine below 32 mph or thereabouts. And I like each shift to occur at or near the same rpm, at a particular throttle-setting. In your case with the Hi-stall TC, IDK if you can make it work the way I like it to, with 3.23s.
      yes, you use that governor by altering it's weight and timing. But that governor is synchronized to your driveshaft rpm. It should NOT need to be changed unless you change the rear gear, or it is synchronized to a previous rear gear ratio.
       
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      • fishmens67

        fishmens67 FABO Gold Member FABO Gold Member

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        Rear tire diameter will have an effect on accurate speedometer reading.
        Your speed may not be what you think.
         
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        • DentalDart

          DentalDart Well-Known Member

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          I understand some of this..

          Currently i do not have a flare up. Just high shift speeds. My rear end used to be 2.76, changed to 3.23 a while ago, revuilt the transmission and necer could adjust the flare up out of the transmission...

          Now put in new tc, new valve body and adjusted the bands per the manual and then adjuated the kd linkage. No more flare up shift just high shift speeds.

          I have part throttle kd and it works, as far as I know. When I slam on the gas it downshifts lol.
           
        • DentalDart

          DentalDart Well-Known Member

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          I'll adjust a touch more.
           
        • CudaFactHackJob

          CudaFactHackJob Well-Known Member

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          Your improper kd adjustment is covering up the real problem causing the 2-3 flare. Is there an orifice plug in your case?
           
        • DentalDart

          DentalDart Well-Known Member

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          No there isnt, but the directions for the shift kits said that is only required in a 727, not a 904.
           
        • abodyjoe

          abodyjoe Well-Known Member

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          my 904 shifts at about 15mph and 30mph at light throttle. no flare ups at all.
           
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          • CudaFactHackJob

            CudaFactHackJob Well-Known Member

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            Is your reverse delayed? That is; when you put it into reverse, does it take a second or two more to drop into reverse compared to drive? If so, the direct pack clutch clearance is too much.
             
          • DentalDart

            DentalDart Well-Known Member

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            No, when I shift to reverse it goes right in gear and will start backing right up if you let off the gas.
             
          • DentalDart

            DentalDart Well-Known Member

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            Mine would shift at those speeds too... if I had a full manual vb... or just did a manual swap...:rofl:
             
          • CudaFactHackJob

            CudaFactHackJob Well-Known Member

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            Is your band set too loose? What was the front clutch clearance?
             
          • CudaFactHackJob

            CudaFactHackJob Well-Known Member

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            18 and 28 is a little late for normal driving.
             
          • DentalDart

            DentalDart Well-Known Member

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            Shoot you are asking questions... lol. I'll have to go back and look.

            Picture of front clutch, we were a little tighter than factory clutch clearance spec. (I believe factory spec is somewhere around .028 clearances)

            I readjusted the bands to rear band 4 turns out and front band 1 1/2 turns like turbo action directions say.

            This is the vb and kit, I should note, it was not letting me manual shift last time I took it out.

            I hate transmissions... i should have a professional do this lol. Who lives by Springfield missouri? :lol:

            I'll mess with the kd adjustment tomorrow and take it for some spins.

            20220609_202307.jpg

            20200422_215349.jpg
             
          • CudaFactHackJob

            CudaFactHackJob Well-Known Member

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            What is that last pic of? Did you install that drum like that exactly?? There is NO retaining ring. What is going on here???
             
          • DentalDart

            DentalDart Well-Known Member

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            There is a retaining ring, was just showing a picture of when we did it and how tight it was.
             
          • oldkimmer

            oldkimmer FABO Gold Member FABO Gold Member

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            Was it like the pic with 18 thou and then u installed the snap ring? Or? Kim
             
          • Bewy

            Bewy Well-Known Member

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            The 727 is a beefy trans but Ch made a monumental error in the design. The 2-3 shift: trying to 'time' the disengagement of a band that is underload & then have a clutch engage with perfect timing so that there is no flare up or bind up is an exercise in futility when you also factor in varying speeds, fluid pressures, friction material wear, etc.
            Ch fiddled with varying ratios of k/d levers, but it is the concept that is at fault. And having a band try & stop a huge, heavy, spinning drum.....At least they made the adjustment external for the inevitable wear.
            GM got it right, they used sequential clutch application.
             
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            • CudaFactHackJob

              CudaFactHackJob Well-Known Member

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              But in that pic, there's no room for a ring to fit into the groove. Who told you .028? I'm thinking your direct clutch is fried. The pic and your explanation make no sense. Have you looked at pics of other assembled direct drums? That looks like a slant six drum that you tried to put an extra steel and friction in like a V8 drum. If you try that, you have to use an extra lower pressure plate from a forward drum. That drum has a lower retaining ring groove than a V8 drum. And that's not even a pressure plate on top; that's just a steel.
               
              Last edited: Jun 10, 2022
            • oldkimmer

              oldkimmer FABO Gold Member FABO Gold Member

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              He must of just been checking to see if he could fit an extra clutch and steel. He will have to remove the top steel, the clutch plate and the next steel to be able to fit in the pressure plate. So assuming steels are .062 each and a clutch plate is .075 so that is .199 thou that he removes. Pressure plate approx .180 thou he saves .019 though. No room for a .60 snap ring yet. Of curse in just assuming these measurements. Kim
               
            • toolmanmike

              toolmanmike Moderator Staff Member FABO Gold Member

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              Adjust the bands. it might help. You might have a internal seal leaking that is being camouflaged with increased line pressure.
               
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              • CudaFactHackJob

                CudaFactHackJob Well-Known Member

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                Nah, his tranny is a mess inside.
                 
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                • oldkimmer

                  oldkimmer FABO Gold Member FABO Gold Member

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                  Let’s give him a chance to explain. Kim
                   
                • CudaFactHackJob

                  CudaFactHackJob Well-Known Member

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                  Ok, hold my beer..."A picture is worth a thousand...'explanations'...." He thought it was easy....and it was...but he went the extra mile and screwed the pooch. People, these transmissions are SIMPLE...the very simplest (is that a word?)..But AT LEAST put it back together the same way it WAS....or come in here and ask one of the helpful samaritans on board...I still can't believe the first trans (a 904) that I managed to get bolted back together (1980) actually worked at all, but no leaks, had reverse and third back and it shifted very well...I had no idea except that I KNEW it wasn't going to work..but it did.
                   
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