3rd Gen Ram Tech2002-2008 Rams: This section is for TECHNICAL discussions only, that involve the 2002 through 2008 Rams Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
I'm trying to get some definitive information about the 545RFE (aka.
5-45RFE) transmission available in the HEMI Ram. It's billed as a
five-speed auto, but I've read that it's really a four-speed with two
second gears, depending on whether you're upshifting or
downshifting. I've also read that it's a five-speed PLUS a
kick-down gear. When trying to figure out the various gear ratios
I can get my '04 Ram 1500 QC into, I count at least seven, including TC
lock-up in the 1:1 gear and overdrive.
Somebody please set me straight. How many different forward gear
ratios are there in the 545RFE? How many different gears can I
kick-down into at any particular speed? Any good reference sites
or documents available online?
I may be way off but I was under the impression that it's a five-speed,
but 4th and 5th are both "overdrive" gears. When you stomp on it
at speed, it's actually dropping into 3rd (or 2nd I suppose, if
you're towing or going up a steep hill!)
Chrysler's newest transmission in trucks is called either the<FONT color=#000000> 45RFE </FONT>or 5-45RFE. RFE stands for rear wheel drive, fully electronic. These transmissions despite having different names are basically the same, except that the 5-45RFE has an extra overdrive ratio. the 5-45RFE does indeed use 5 ratios in its normal shift sequence. the 45RFE only uses 4 speeds in a normal shift sequence. BOTH trannies have alternate second gear ratios for kickdown. for instance when you floor the throttle at highway speeds the tranny will downshift to the taller numerical second gear ratio to help smooth out the downshift. Since the 5-45RFE goes through 5 ratios in a normal shift sequence, chrysler can call it a 5 speed automatic. Chrysler calls the45RFE a multispeed tranny simply because of the two second gear ratios, but in a normal shift sequence it only uses 4 gears.
The 5-45RFE is supplanting the 45RFE in *******ly all the trucks. Presumably that extra overdrive ratio in the 5-45RFE helps fuel mileage. Chrysler is able to "electronically" get another ratio out of the 45RFE planetary gearset. The extra ratio makes the tranny a 5-45RFE!
The 45RFE four speed plus kickdown automaticAn electronically-controlled transmission with five forward ratios including an alternate second gear ratio for improved performance for passing and better fuel economy was designed specifically for Jeeps (but was used later in Dodge trucks) starting with the 1999 Grand Cherokee V8.
The transmission features a tall, 3.00:1 first gear that gives the driver better initial acceleration. Real-time driver adaptive shifting fine-tunes the shift pattern to the driver, while an alternate second gear ratio gives the driver five forward ratios. During acceleration, second gear has a ratio of 1.67. Depending on speed and throttle position, both this gear and an alternate 1.50 second gear ratio are available for kick-down operation, making the down-shift smoother. Its reverse gear ratio is equal to the first gear ratio, to allow for heavier loads.
Other features include three planetary gear sets that combine the widest range of gear ratios available in any transmission in its class. Combined with precise step selections, this brings smooth shifts and maximum power and optimal fuel economy.
The transmission is built at the Indiana Transmission Plant in Kokomo, Indiana, in an all-new 1.2-million square-foot facility.
Thanks for the replies! When I first read the text you quoted from allpar.com,
it wasn't clear to me that there were SIX available forward gear
ratios, five used during upshift and a second Second gear (1.50:1) used
during downshift. Pretty smart transmission!
Any idea what they meant by stating, "... [with the 5-45RFE,] Chrysler
is able to 'electronically' get another ratio out of the 45RFE
planetary gearset"? What electronic wizardry gets us another
ratio? Is it truly five unique planetary gear combinations on the
way up? Is the second overdrive an additional physical ratio?
I really appreciate the education. When you've got the first HEMI
on the block, you get lots of questions from friends and
acquaintances. I need to UNlearn the misinformation (ie. the
dealer said this was a Mercedes 5-speed, which allpar.com specifically denies) and replace it with actual facts.
ps. I also renamed the thread from "545RE" to "545RFE". Typos don't
I found this on another site from CW who is a Chrysler Tech:</P>
Yes it is possible to update the controller to 5-45rfe specs. I think the 02 is that way out of the factory. Think there is a bulletin for exhaust drone at highway speeds and the flash to fix it updates the 45rfe to 5-45rfe programming. All it does is give you a double overdrive trans and lower cruising rpm on the highway. </P>
Form another user:</P>
1st - 3.00:1
2nd - 1.67:1 (upshift)
2nd - 1.50:1 (downshift)
3rd - 1.00:1
4th - 0.75:1
In Dodges it comes with a 3.55 or 3.92 diff ratio, Jeeps it came with a 3.73.
Yes it can magically make another gear in the transmission. If you know how a planetary gear system works it is easy to do. There are no bands in the 45rfe just clutches that hold and release certain parts of the plaetary gear. giving you different ratios including the double overdrive in the 5-45rfe. There are three planetarys in the 45rfe. All done with the computer telling which solenoids to apply or release in what ever order you want.
I took a little calculating but the 45rfe has the possibility of 8 forward gears and 3 reverse.
Well, if they stayed true to tradition, the first number (kinda messed up by the 5-45 of course) indicate the number of gears, the second number represents the amount of torque it is designed to take. So a 45rfe would be a 4 speed tranny rated at 500 ft lbs of torque.