Only difference in 45RFE and 545RFE is software???

[Dr. Righteous]

I ran across this while hunting tranny information.
This seems pretty strange. I can't believe that is the only difference in the 2 transmissions.

http://www.dakota-durango.com/forum/...ad.php?t=52534

[dodger1]

Yeah, how can the O/D ratio be changed from .75 to .64 with just a software app? And just how many "gears'" are in the 45RFE anyway?

[dgc333]

Those guys are smoking crack if they think they are getting a different OD ratio.

All the 45RFE's were 5 speed trannies but the software would chose between two second gear ratios 1.5:1 and 1.67.1.

The OD ratio on all 45RFE's is .75:1. The 545RFE changed the OD ratio to .67:1.

The software in the 45RFE would choose which second gear to use depending on conditions. You certainly could use different software and make it into a 5 speed by using both second gears all the time but you won't be getting a different 5th gear ratio.

[BelvedereII]

Pretty good crack too, I guess, since the claim is they could get 8 forward gears out of it if they wanted. 3 planetaries is one more than two.

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.

My '04 Dakota 4.7L 4x4 has the 545RFE, with two overdrives, and when towing I'd like to be able to limit that to just the .75 ratio to get it to stop downshifting in certain conditions. I just read that the '09 Ram lets you limit the highest gear. In my truck I can only lock out both overdrives, not just the highest. It's the tranny used behind Hemis in the Ram, so I hope it holds up well in my Dak.

B II

[Dr. Righteous]

Originally Posted by BelvedereII

Pretty good crack too, I guess, since the claim is they could get 8 forward gears out of it if they wanted. 3 planetaries is one more than two.


My '04 Dakota 4.7L 4x4 has the 545RFE, with two overdrives, and when towing I'd like to be able to limit that to just the .75 ratio to get it to stop downshifting in certain conditions. I just read that the '09 Ram lets you limit the highest gear. In my truck I can only lock out both overdrives, not just the highest. It's the tranny used behind Hemis in the Ram, so I hope it holds up well in my Dak.

B II

Our '04 Durango Hemi has the 545RFE and at first I was dubious of it because I didn't know anything about these. But all the research says this tranny is a real winner. The only problems I have come across have been nothing more than a firmware flash to alter shift points.
Yeah, one reason we purchased this beast was because we wanted to tow a trailer with it while having comfort for family members. I was quite annoyed when I found out the TOW/HAUL feature only disables ONE of the overdrive gears and alters shift points. But so far we have had NO problems with the engine lugging on hills. It works great.

[BelvedereII]

My truck has changed its shift points from time to time, driving over the same routes around home, and I figure it "learns" driving mannerisms as some claim is the case with computer control.

The one thing I'd most like to change is getting the cruise control to let the engine go to an "idle" setting. It's always feeding gas when on cruise, and that lets the truck really start rolling downhill which is "solved" by the tranny SLAMMING into 3rd to slow it down. On the same hilly road south of me, if I punch off the cruise as it crests a grade (or starts down the other side, depending on the hill itself) the engine will go to idle and the truck maintains speed or slows down. If the cruise is left on, the truck will quickly gain speed then downshift in an attempt to put passengers through the window.

Yeah, I miss my old Dakota's manual transmission.

B II