"PATC has developed a 6-pinion planet gear set for 700R4 / 4L60E transmissions. This will be the biggest thing in 700R4 advancements in years. These will have a 2.66 to 1 first gear, 1.55 to 1 second gear, 1 to 1 third gear and .64 to 1 overdrive ratio. This is a 36% overdrive making this one of the best overdrive ratios around. The 1st to 2nd RPM drop between gears would be slightly less than the RPM drop on a 200-4R transmission. This is what people have been asking for, for years. These will work on any 4L60E type transmission without a gear ratio error code, if the PCM is modified. This gear set is used to reduce torque multiplication / rotating speed in the transmission in first gear. This improves track applications that overpower the rear tires upon launch. This is common with numerically high final drive ratios. (IE 3.06). Now you will have a choice between the wide ratio or the new close ratio gear sets. It has been reported that the 2.66 gear set could lower your quarter mile time as much as 4/10 of a second over the 3.06 gear set. Plus better mileage and lower RPM with the .64 to 1 overdrive. The first 50 are in production now and the approximate release date is 2-1-2008. "
http://www.gmfullsize.com/forum/showthread.php?t=106786