I found this on Wikipedia:

The 45RFE and 545RFE automatic transmission in the WJ was notable. It included three planetary gear sets rather than the two normally used in a four-speed automatic. This gave it six theoretical speeds, and it would have been the first six-speed transmission ever produced in volume, but it was programmed to only use five of these ratios. Four were used for upshifts, with a different second gear for downshifts. Although five of the six ratios were used, Chrysler decided to call it a "4-speed automatic". In 2001, the programming was changed to make use of all six ratios. Rather than have six forward gears, the transmission was programmed to act as a five-speed with the alternate second gear for downshifts. The rpm at 70 miles per hour (110 km/h) on a 545RFE is 2000 rpm, 200 rpm less than the 45RFE programming. 1999 and 2000 model year WJ owners can have their 45RFE transmission's programming flashed to enable the extra gear as both transmissions are physically the same. The 42RE 4-speed automatic remained the transmission for the Inline 6 engine. It had slight changes from the previous model Grand Cherokee.

Very interesting.

If Chrysler had half a brain, they would have made it an ACTUAL 6-speed for the diesels, with an even deeper overdrive ratio for the #6 gear. The diesel has plenty of torque to do that, but the CRD also has the wrong gearing in the pumpkins. I don't think my RPM was 2000 at 70mph, I seem to remember it was higher, like 2200-2300. That would be getting outside the torque curve.

My family just bought a Chevy Equinox (2013) with the 2.3l (I think) 4-cylinder squirrel-drive. Not a hybrid, and slightly bigger than our previous Mercury Mariner / Ford Escape hybrid with a 2.3l engine and CVT transmission. The thing has a true 6-speed and at 70mph, is turning LESS than 2000 rpm.

The hybrid weighs about the same, and struggles to find 28mpg at 70mph. This thing gets 32 at 70mph - and doesn't feel underpowered in the slightest.

Meanwhile, the Jeep Libertys are smaller, weigh more (by several hundred pounds), and also struggle to find 30mpg downhill. Sad - they have more than enough power for that.

If Chrysler had half a brain, they would have made it an ACTUAL 6-speed for the diesels, with an even deeper overdrive ratio for the #6 gear. The diesel has plenty of torque to do that, but the CRD also has the wrong gearing in the pumpkins. I don't think my RPM was 2000 at 70mph, I seem to remember it was higher, like 2200-2300. That would be getting outside the torque curve.

My family just bought a Chevy Equinox (2013) with the 2.3l (I think) 4-cylinder squirrel-drive. Not a hybrid, and slightly bigger than our previous Mercury Mariner / Ford Escape hybrid with a 2.3l engine and CVT transmission. The thing has a true 6-speed and at 70mph, is turning LESS than 2000 rpm.

The hybrid weighs about the same, and struggles to find 28mpg at 70mph. This thing gets 32 at 70mph - and doesn't feel underpowered in the slightest.

Meanwhile, the Jeep Libertys are smaller, weigh more (by several hundred pounds), and also struggle to find 30mpg downhill. Sad - they have more than enough power for that.