governor gear and shift points

[87geeinn]

Correct me if I'm wrong: I installed a new transmission which has a 13-tooth governor gear installed vs. the stock 11-tooth gear. I immediately noticed that the car shifts early in the RPM range. Not terrible, just lower than I am used to. Is this because the governor gear is spinning slower compared with the output shaft speed, thus requiring more RPM to cause the weight(s) to move outward?

I don't understand how shaving weight off of the small weight will raise shift points in our cars since only the small weight is held outward by a spring. I would think this would leave it up to the movement of the large weight to control things. What am I missing? Learn me.

 

[TexasT]

This is a novice view(mine). There is pressure pushing on the check ball that is being held back by the spring and the weight imposed by the centrifugal force if the weight. Lighter weight equals less force holding the check ball. That is how I see it. There is also the shift sections of the valve body with springs that regulate what speed/rpm the trans shifts. It gets deeper in the GM principles of operation manual. There are many factors that goes into where the trans shifts.

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[mikestertwo]

I think you are confusing the driven part of the gear vs. the speedo drive portion of the gear. I'm pretty sure all the governor gears have a 14 tooth driven gear off of the output shaft. The differences are the speedo drive portion. The governor is spinning at the same speed it's the weights and the springs that make the difference plus the calibration of the valvebody. Did you replace the transmission with the same code trans? Was the new trans recalibrated? Need more info on the original trans you replaced vs. the new one you just put in.

 

[87geeinn]

@mikestertwo: It's a new BRF valvebody transmission built by one of the top vendors and was dyno tested for proper operation prior to shipment. The gears available are 10, 11 (orange stock GN gear), 12, and 13 tooth governor (drive gears) and 27 through 31 tooth speedo gears (driven gears) of which are all color coded to indicate their tooth count. In my case, I have a 13 tooth drive gear and a 30 tooth driven speedo gear installed, which equates to a seven mph speedometer error reading (fast) on the highway. I tested it the other day to confirm.

I called the builder and he explained it a little more in depth and I sorta understand. In any event, I am going to swap the governor gear out from my spare trans which has a stock 11 gear governor gear in it and see if that raises the shift points. The car shifts fine and nothing seems out of the ordinary, I would just like it to shift ever so slightly higher in the RPM band in all gears. What I was getting at is that a governor drive gear with a higher tooth count would spin slower in relation to the output shaft given the higher tooth count, thus causing shift point to move to a different point in the RPM band. Now that I think about it, a slower spinning governor drive gear would--in my theory-- require higher RPMs/vehicle speed to cause the gov weights to swing outward and affect shift points. I don't know anymore. Thats' why I'm not a transmission guy.

 

[VIN7]

The plastic gear will spin at the same rpm regardless of tooth count. The spring and weights determine (for the most part) shift points based on when the checkballs unseat. The plastic gear tooth count affects on one thing, the gear on the end of the speedo cable which drives the speedo needle.

You may "see" shift points change on mph, but the reality is that the trans is shifting at the same rpm but the speedo error will report a different shift mph.

 

[87geeinn]

@VIN 7: I totally understand now. Thanks.


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[INEEDAGN]

As stated above, there's 2 sets of gears on the governor gear. The ones that mate to the output shaft are the same tooth count regardless of gear color. Different gears only affect the speedo reading.

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[87geeinn]

Yep, the way VIN 7 explained it, it made sense. I took another look at the governor gear and the light bulb in my head went off when I saw the two different sets of teeth (the one driven by the output shaft and the one that drives the speedo driven gear).


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