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-   -   Changing shift points in a GM 200R4 OD transmission (http://www.hotrodders.com/forum/changing-shift-points-gm-200r4-od-transmission-221004.html)

willys36@aol.com 06-25-2012 09:03 PM

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.

THERACER 06-26-2012 10:46 AM

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

rick 427 06-26-2012 01:56 PM

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.

willys36@aol.com 06-26-2012 09:26 PM

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.

willys36@aol.com 07-05-2012 02:22 PM

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.

Fstarocka 07-07-2014 11:10 AM

perfect! will be doing this mod when I pull the trans this week - pics and article saved on google drive!


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