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Old 06-25-2012, 10:03 PM
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Changing shift points in a GM 200R4 OD transmission

When you upgrade to a 200R4 OD transmission to get the benefits of the 0.67 overdrive, it is rare that the automatic shifting sequence occurs at the proper speed. Most likely you have lower rear end gears and a cam so you want the shifts to occur at a higher RPM but the donor tranny is likely set up for a grocery getter and results in 1-2, 2-3 shifts way too slow for your setup. Thus you are stuck with manual shifting which is fun but there are times you want to set it in drive and run it automatically.

A lot of people suggest changing the shift points by adjusting the throttle cable. DON'T DO THAT! That cable needs to be set properly and left alone. It is the governor that sets the shift timing and you have to modify it.

Here is how we did it. Basically we cut down the weights on the governor which is the proper method.

We ended with perfect shift points for the street; ~2000rpm @ 1-2 and 3000rpm @ 2-3. We havent tried it yet but I assume at WOT the shiftw will rise accordingly to higher in the power band.

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Old 06-26-2012, 11:46 AM
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did you buy the recalibration kit and install the lightest weights ?
i have a 700r4 with a 4:56 and 31" tires with the same prob.

thanks , ROGER
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Old 06-26-2012, 02:56 PM
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There were several factory gov weight and spring configurations for the 700,depending on the vehicle....I believe the 4cyl trucks and the corvette had the lightest weights....a TRANSGO calibration kit PN K61931S gives you several weight/spring options to adjust shift timing.
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Old 06-26-2012, 10:26 PM
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Unfortunately the 200R4 has a totally different design governor from the 7004R. Whereas the latter has governor tuning kits and I think has access to the governor from the outside of the tranny, the 2004R has no tuning kits. You are on your own when it comes to tuning with no help from the factory or from tranny shops. You have to cut off mass from the weights by the cut and try method. The principles are the same though; NEVER adjust the throttle cable to change shifting characteristics on either tranny and lighten the centrifugal weights on the governor to raise the shift RPM.
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Old 07-05-2012, 03:22 PM
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UPDATE: I finally got a chance to drive the car. Prior to that I was taking my grandson's word for how it is shifting. The new governor is PERFECT! At light throttle it shifts @ 1800-2200rpm, right in the power range. At aggressive part throttle, shift points raise a few hundred rpm (2600-2800rpm), again right in the power range. I am confident if we needed full throttle acceleration, shift points would pop up to the right higher range.

In summary, the weight we trimmed as described above was perfect for our street setup.
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Old 07-07-2014, 12:10 PM
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perfect! will be doing this mod when I pull the trans this week - pics and article saved on google drive!
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Old 10-03-2014, 06:40 AM
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Quote:
Originally Posted by willys36@aol.com View Post
UPDATE: I finally got a chance to drive the car. Prior to that I was taking my grandson's word for how it is shifting. The new governor is PERFECT! At light throttle it shifts @ 1800-2200rpm, right in the power range. At aggressive part throttle, shift points raise a few hundred rpm (2600-2800rpm), again right in the power range. I am confident if we needed full throttle acceleration, shift points would pop up to the right higher range.

In summary, the weight we trimmed as described above was perfect for our street setup.
Do you remember how much you "shaved off" the weights? I'm assuming not much. I'm very good with a caliper and 48" belt sander! LOL 1/32? 1/16? That I can afford! LOL Can't afford the $60 kit to use only one set of each and then toss the rest in my tool box to sit for the next 20 years.

Mark
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Old 10-03-2014, 07:16 AM
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Quote:
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Do you remember how much you "shaved off" the weights? I'm assuming not much. I'm very good with a caliper and 48" belt sander! LOL 1/32? 1/16? That I can afford! LOL Can't afford the $60 kit to use only one set of each and then toss the rest in my tool box to sit for the next 20 years.

Mark
A 200-4r governor is not same design of the T-400 governor if that is what you are looking for information on.
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Old 10-03-2014, 09:25 PM
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Not sure how it got here but my 200 4r had the same problem. I cut down the small weight to 16.5 grams and removed the large weight spring. I did remove some weight from the large weight, but not much. It lets me shift at 20 mph to second when it warms up. The problem was the 2-3 shift. To get that up, I shimmed the 2nd gear shift spring in the valve body by using a small metal shim that was the thickness of a dime. That let the tranny to stay in 2nd till about 33-35 mph. I didn't do anything with the 3rd upshift valve because I hold it there and only us 4th after I'm out on the open road. Each one of these trannys acts so different depending on how it was built, weight of vehicle, gear ratio and ect. . I think the tranny pressure developed by the pump (valve sizes ), affects shifts, more than we think. To go hand in hand with all the other variables such as clearances, and the all important separator plate modifications. I'm sure if I used my stand by tranny, it would not act like the first one.
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Old 10-07-2014, 08:37 PM
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Why did you not use a BGN part or did you try it and it not work?
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