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A tale of two Governors (or which is best?)

Discussion in 'The Garage' started by BadDog, Sep 6, 2004.

  1. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    The two th350s in my possession have different governors in them. The governor from my old th350 (built to unknown specs) has much lighter springs than the new one. The new one has noticeably heavier springs. I know what the governor does, and I suspect the one from my old tranny is the one I'll want to use, but is there any way to figure out exactly what the differences are going to do after the fact (i.e. Not having a set of springs to choose from, but just taking what happens to be there). Are the springs color coded? Looks like the ones in my old governor were white if that matters. And I thought heavier springs would raise the shift points, and lighter ones would lower it. Is that right? If so, maybe I want the springs from the new governor?

    If I do want to keep my old governor (which is what I think I want to do) the drive gear is busted and shaft is scored from the broken case. If I'm right, I can just use the head assembly (weights and springs) from mine and the shaft from the new one and that should get me what I want. Correct?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes you can use the weights and springs, it should act exactly as it did in the old transmission.

    Heavier weights increase the shift RPM, but I don't know how the springs play into it. I could be wrong, but I have a feeling they are just there to keep things in place, as opposed to affecting shift timing, at least as compared to the weights.

    Someone (TCI? B&M?) makes governor kits, to change shift points, might want to look into those to see what pieces they include. Can probably even find a writeup online about governor operation that might help you make a decision.
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Update:

    Looking more carefully at mine, I realize that one spring is white, the other is yellow. /forums/images/graemlins/crazy.gif

    And the one from the new trans is clearly purple once I got it in a good light.

    Are there markings on the weights to differentiate them?

    And I thought it was lighter weights move the rpm up, thereby reducing the centrifugal force on the stem. To reach the same force, higher rpms would be required, thus raising the shift point. No?
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I believe you are correct. I have heard of people grinding their weights to increase shift points.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Since it works on centrifigal force, heavier weights take longer to swing out, which moves the valve, no?

    I was told I was wrong before, I thought lighter weights moved shift points up. But since heavier weights would take more RPM's toswing out than lighter, it made sense to me. Right?
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Heavier weights would take LESS RPM to swing up. Force = Mass x Acceleration /forums/images/graemlins/thumb.gif
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    That is my thinking exactly.

    But it was bothering me that I did not understand exactly how it works. So I went out and played with it a bit. This is what (I think) I figured out...

    The governor works by balancing centrifugal force against hydraulic pressure.

    RPMs are controlled by output shaft.

    The shaft has two primary pieces, the shaft body (also a bearing surface) and the stem inside.

    The head is composed of a pair of assemblies, each consisting of an outer weight, a spring and an inner lever. The spring is oriented between the inner lever and outer weight such that the inner lever is pushed out by the weight swinging out. But the lever is "L" shaped and the leg hangs into the center over the stem so that the weight/lever combo swinging out pushes the stem down into shaft.

    The stem inside is actually a simple multi-surface piston/valve combo. There are 3 slots in the shaft which allow fluid under pressure to enter and push the stem out into the head. As the stem moves out, the weight/lever assembly is pulled in. The slot opening also controls fluid access to drive parts of the throttle body.

    When the head spins, the outer weights want to push out radially along the rotational axis. This force is countered by the stem trying to push out toward the head (due to hydraulic pressure) against the inner levers, thereby attempting to pull the rotating head in (against the centrifugal force). The only coupling between these inner levers and the outer weights is the spring which attempt to keep the inner lever moving along with the outer weight.

    So, here are (as I see it) the relevant adjustment points.

    1) Lighter weights would raise the shift points by allowing the stem to have sufficient strength to push out on the levers which, in turn, passes the force along the springs and pulls in the weights which lack the mass to overcome the hydraulic force on the stem. Once they do get sufficient RPMs to over come the stem and push it in, a shift occurs and fluid/pressure is rerouted to push it back out again (by pushing harder - more piston heads and more area under pressure) till it overcomes the weights and/or the springs again, resulting in another shift.

    2) At first I couldn't figure out how heavy/light springs would affect things. Basically the only thing it can effect is the relationship between the lever and the weights. One possibility is that lighter springs will allow the inner lever to be pulled in more easily (by the stem pressing out) without having to bring the outer weights with it. It seems that this would allow the weights to swing out sooner than their mass vs. the hydraulic pressure would allow, effectively reducing the maximum strength of the weights against the stem. However, it seems that if this were the case, then it would get into a state where the weights were out, but the stem would not be pressed in by them, so there would be no shift and you effectively have a sort of stale-mate; unless other internal forces are at work that would break it…

    Not sure yet exactly how that applies…

    Maybe softer springs speed the stem's journey back out after a gear shift, thereby hastening the transition from one state to another (with respect to the valve function of the stem). In other words, there would be less lag time between shifts. What I am guessing is that heavier springs would (more-or-less) force the weights to come in, fighting centrifugal force and inertia, before the stem could move full circuit. And lighter springs would allow the stem to move quickly, and then the springs drag the weights along a moment later.

    Or maybe the weights work for part of the equations, say at lower RPMs, and at higher rpms, the CF simply grows too high and the springs provide a somewhat steady rate to work against for the upper RPM work? There is also the possibility that the smaller levers themselves act as much lighter weights applying their centrifugal force in concert with the springs to help overcome the stem when the weights are already fully extended by compressing the springs. In this case, it would seem that the springs/levers control the higher gear shifts at speed, with the outer weights controlling things at lower rpms.

    Does this make sense?

    I'm hoping someone who knows tranys will clear this up for me. I suppose it would be useful to go through the hydraulics diagrams to see what gets/receives pressure via. the governor when, but it's getting late and I have to work tomorrow.

    Bottom line is I've got 2 governors of unknown origins. Each appear to have the same weights, but they have different springs. My old one is much lighter and has 2 different rate springs in it. It is known to have been "built" but the exact spec is unknown. The one I was going to put (in until I found out the bell is cracked) is supposed to be stock (to the best of the seller's knowledge) but has a matched pair of considerably heavier purple springs.
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Are either of your governors from the Diesel engine that came in the CUCV?

    When tj comes back tomorrow, he's good with autos, hopefully he can help you out.
     
  9. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    No, the diesel governor is still in my Th400/205 in the boys truck.
     
  10. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Just go to your local auto parts store and buy a new complete governor assembly, they are cheap at only $20.00. I can buy it new from the dealer for $25.00 even.

    I know you haven't said anything about it but my tranny shop told me how to make a tranny shift harder as well. All you need to do is remove the spring from behind the servo piston. What a difference that makes. Mine was shifting waaay too hard so i reinstalled the spring and now it shifts much softer and doesn't feel like my tranny is going to break in half anymore. /forums/images/graemlins/thumb.gif
     
  11. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    to tell you the truth, ive never really studied about the governers much.

    what i do know is the fluid pressure keeping the valve in place is compressing the springs as the outer weights swing out and once the inner weights over come the fluid pressure is when the valve moves and it shifts.

    as the engine RPMs increase, so does the line pressure, so the weights are working harder to overcome the pressure. but as the output RPM increased the weights spin faster and can push the valve back easier.

    a stronger spring or heavier weight is gonna work against the fluid pressure's side so its gonna shift sooner. a lighter weight or weaker spring is gonna make it shift later, simulating a harder shift because its higher into the RPMs where the fluid pressure is greater.

    im not sure about the whole spring/weight thing. i think they go hand in hand, lighter spring gets a lighter weight, but i coud be wrong.

    i have 2 governers here, 1 is out of a th350 that shifted quite hard aided by i believe a B&M shift kit, and the other is a stock 700r4 governer. the 700r4 has heavy weights, the th350 has light weights, with one weak spring and a strong spring. the 700r4 spring rates are closer together than the th350 spring rates.

    the th350 and 700r4 governers are identicle except where the weights are at.

    the springs are color coded, not sure on what the rate is for each color. i have a red and green one in the th350 gov. and what looks like white and brown in the 700r4 gov.

    i would take the springs out of your old gov and put them in the new gov. if the wieghts looks the same, then they probably are.

    hope this helps any. /forums/images/graemlins/waytogo.gif
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    If you've got time, check gnttype.org out, if they still exist. Haven't had cause to go there in some time.

    That seems like where I had seen it, but somewhere on the net, I KNOW there is an article about shift timing and modifying the governor for how you want it, and it applied to GM trannies.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, these guys don't even mention the weights, but they do say change the springs:
    Transmission Place

    All I found through a quick search.
     
  14. Blue85

    Blue85 Troll Premium Member

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    It seems that you have it right. Lighter weights raise the shift points. Lighter springs will tend to lower the shift points, but it is not that simple.

    The springs control the interaction between the hydraulic pressure and the centrifigal force on the weights. This effects how much the line pressure effects shift points. For instance, is there a big effect on shift rpm with throttle position or do the rpms not vary as much?

    The governor weights and springs have no effect on the shift firmness, only the shift point. When the comparison of TV pressure to governor pressure is right, a shift relay valve will slide in the valve body. This is what triggers the shift. The firmness is controlled by line pressure, accumulator setup, apply piston size, etc.
     
  15. Beast388

    Beast388 1/2 ton status

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    If TCI color coded their springs the same as GM, the colors are as follows....

    Low RPM Quick Shifts……….. ……® Shift Points Spread Apart
    Heavy -> Purple - Blue- Green - Yellow - Orange - Red -> Light

    TCI also shows how their weights affect shift point:

    Earlier Shifts…………………………………………® Later Shifts
    Heavy 1—--2-—-3—--4—--5--—6 Light

    All of that info can be found here. /forums/images/graemlins/waytogo.gif
     
  16. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Scott:
    I don't need a governor. I just want to figure out how these work and what the diff is between them. And I know about removing the accumulator spring (not a good thing really) which is a different thing all together.

    All:
    Thanks for the info. Looks like I was pretty close in my pondering. So, the inner levers do act as centrifugal weights as well. But I think there is more. Based on my understanding of the replies, the outer weights could be rigid and it would work the same.

    [Edit]
    In any case, I'll be using the springs and weights (just in case) from the old trans since the new governor appears to be stock with stiff purple springs. Of course that's assuming I can even use the new one which turned out to have a cracked bell housing...
     

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