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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.

Author:	Quiksilver [ Mon Apr 29, 2013 11:51 am ]
Post subject:	Our Boxes
So I read this on another forum. Quote: 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. Is this true for our gearboxes? the whole 5 speed with the alternate second gear?

Author:	audiboy86 [ Mon Apr 29, 2013 12:06 pm ]
Post subject:	Re: Our Boxes
Yes it is you can even swap Ecms between a 45rfe and 545rfe KJ and they will work i have tried it. Also the down shift point is different depending on certain factors which i do not recall. But basically to make a 45rfe into a 545Rfe all that is required is reprogramming of the computer. Which in all honesty helped out gas mileage a ton having that extra gear.

Author:	geordi [ Mon Apr 29, 2013 3:37 pm ]
Post subject:	Re: Our Boxes
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.

Author:	Hexus [ Mon Apr 29, 2013 7:03 pm ]
Post subject:	Re: Our Boxes
geordi wrote: 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. When my f'ing liberty is running, I'm averaging around 34mpg hand tallied.

Author:	Hoosier CRD [ Mon Apr 29, 2013 7:14 pm ]
Post subject:	Re: Our Boxes
My combined city/highway mileage is typically around 26 MPG. I did average 31.5 MPG while driving to Kansas City for Thanksgiving this past year. Didn't have to stop for fuel on a 500 mile trip! Regarding the 545RFE, I thought that I read that it was 3rd gear that had the different ratios-one ratio for going through the gears at normal throttle and one ratio used for passing.

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Author:	joelukex4 [ Tue Apr 30, 2013 11:53 am ]
Post subject:	Re: Our Boxes
geordi wrote: 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. It's amazing the technology advance in 7 or 8 model years. I believe very few if any vehicles had 6 speed trannys in '05 & 06. 6 speed trannys are becoming the low end of the market. Most vehicles are getting 8 speed transmissions now. Look at the new Grand Cherokees. Now hook up 5000 LBS behind that Equinox and lets see what it can do.

Author:	flash7210 [ Tue Apr 30, 2013 12:05 pm ]
Post subject:	Re: Our Boxes
The 545RFE in our CRD actually has 6 speeds. 1st 2nd' (used only as a passing gear) 2nd (shift at about 16mph) 3rd (shift at 28mph, when OD-off you will get TC lockup at about 37mph) 4th (shift at 35mph when OD-on and TC lockup at about 51mph) 5th (OD-on, shift and TC lockup at about 61mph) For those not familiar with how this transmission shifts, TC lockup feels like a gear shift.

Author:	Billy M [ Tue Apr 30, 2013 3:46 pm ]
Post subject:	Re: Our Boxes
Interesting shift sequence. I never knew. I always thought it was shifting into 5th at 51mph and the TC was locking up at 61mph. TC lockup definitely feels like a gear shift. Billy

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