Does tire size and gear ratio change make a big differences in shift point on a 4l60e transmission . Example stock tire 28 inches 3.42 gear ratio , change to 26 inches with 3.73 gears ratio . Will the 26 inches and 3.73 gears ratio change cause the transmission to shift fast and the rpm to be higher . Next question how do you adjust the transmission shift point's on a 4l60e transmission after a gear ratio transmission change.

gear ratio & tire diameters changes will cause the shift points to change. The PCM shifts the tranny at certain programed settings & input from various sensors on the vehicle. If you install larger tires the PCM will think the vehicle is traveling slower, when it is at the same speed that the OE tires produced.





Custom programming or changing the parameters in the PCM with availible softeware for that purpose.

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At the Bonneville Salt Flats... 130mph is known as First gear ...............

yes you will have to change the program the ecm came go to your local gm dealer and ask them to reprogram the pcm it takes about five to ten minutes find a cool shop and ask them to help you out should do it for free if not some dealers charge 1 hour labor me i dso it cause i like to do it drive up to santa barbara ask for chico @ hughes pontiac gmc volvo you need a tech2 to do this after market scanners do not have the capability good luck