Good news for 5-45RFE and 45rfe owners

ManicMechanicJoe · **Posted:** Thu Feb 09, 2006 4:08 am

So I have been doing a lot of searching online to find the spline count on a 45rfe and a 42rfe transmission to see if I can swap my t-case for a 231 from savage...

anyways I found this tidbit from a dodge forum:
45RFE:
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.

5-45RFE:
1st - 3.00:1
2nd - 1.67:1 (upshift)
2nd - 1.50:1 (downshift)
3rd - 1.00:1
4th - 0.75:1
5th - 0.67:1

From CW:

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.

Here is a link to the forum I found it in:

http://www.dodgeforum.com/m_7948/mpage_1/tm.htm#8017

So the 45rfe really has 5 speeds and the 545rfe has 6 speeds. Since the planetary gears are controlled by solenoid which is electronically (computer) controlled. Seems to me if someone reflashed the tranny's computer we could get a lot more gears for fuel economy and a drivetrain that is better suited for the wide variety of terrain our Jeeps see. What do you all think?

BTW-if anyone has a service manual-could you please tell me the spline count on the output shaft of both the 42rfe and the 45Rrfe?

uvalax236 · **Posted:** Thu Feb 09, 2006 10:14 am

So are you saying that I can have 5 gears in my 02 KJ?

the1jferg · **Posted:** Thu Feb 09, 2006 10:33 am

I'm ready for it.

ManicMechanicJoe · **Posted:** Thu Feb 09, 2006 11:25 am

uvalax236 wrote:

So are you saying that I can have 5 gears in my 02 KJ?

Yes and no. Since two gear ratios are used for 2nd it is still considered a four speed because you only shift 4 times each way. So really it is a 4 speed but with 5 ratios. I don't understand the advantage to this yet...
But it is cool that you can add gears as you choose with a little programming know how.

Jeepjeepster · **Posted:** Thu Feb 09, 2006 1:23 pm

This tells me nothing for my poor little 42rle?!? :cry:

ManicMechanicJoe · **Posted:** Thu Feb 09, 2006 1:50 pm

this tells you that you need to dump your 42rle and get the stronger 45rfe with TWO second gears and a possible 8 forward gears and 3 reverse (you could do 60 in reverse :twisted:

) !!!!!!!!!!!!!!

Jeepjeepster · **Posted:** Thu Feb 09, 2006 5:47 pm

ManicMechanicJoe wrote:

this tells you that you need to dump your 42rle and get the stronger 45rfe with TWO second gears and a possible 8 forward gears and 3 reverse (you could do 60 in reverse :twisted:

) !!!!!!!!!!!!!!

If I had the money ManicMechanicJoe I would.

NU ARTY BOY · **Posted:** Thu Feb 09, 2006 7:11 pm

I remember reading that when that trasmission first came out in the WJ the reason behind it was for towing/ need for heavy acceleration. At higher speeds (45+ mph) the trans would use the higher ratio "second" gear but under lower speeds, or when the OD has been turned off the trans would use the lower ratio "second" gear. A lot of it was to get the WJ to have better fuel economy and yet better acceleration.

BlackOps · **Posted:** Fri Feb 10, 2006 1:48 am

What does my 2004 Rennie have? Got the limited slip if that makes a difference....

--BlackOps

NU ARTY BOY · **Posted:** Fri Feb 10, 2006 2:45 am

All 2004s have the 42rle.

jeepkj02 · **Posted:** Fri Feb 10, 2006 11:19 am

NU ARTY BOY wrote:

All 2004s have the 42rle.

I thought my 2002 sport had the 42rle :?:

the1jferg · **Posted:** Fri Feb 10, 2006 11:30 am

45RFE on my 2002

kjrenegade · **Posted:** Fri Feb 10, 2006 12:13 pm

I've known this about the 45 for a while, but I've yet to hear of anyone being able to make it work..

Plus, I wonder why they limited the 45RFE in the Lib to just the 4 forward gears, instead of the 5 in the 5-45RFE used in the WK.. Would it have something to do with the power of the 3.7 vs. the 4.7 or Hemi?

Guest · **Posted:** Fri Feb 10, 2006 12:50 pm

kjrenegade wrote:

I've known this about the 45 for a while, but I've yet to hear of anyone being able to make it work..

Plus, I wonder why they limited the 45RFE in the Lib to just the 4 forward gears, instead of the 5 in the 5-45RFE used in the WK.. Would it have something to do with the power of the 3.7 vs. the 4.7 or Hemi?

I know for the CRD we got the 5-45RFE because the diesel is only effective in a very limited rpm range. The extra gear helps us keep in the sweet spot of 1600rpm to 2000rpm better for normal driving.

Jeepjeepster · **Posted:** Fri Feb 10, 2006 1:17 pm

kjrenegade wrote:

I've known this about the 45 for a while, but I've yet to hear of anyone being able to make it work..

Plus, I wonder why they limited the 45RFE in the Lib to just the 4 forward gears, instead of the 5 in the 5-45RFE used in the WK.. Would it have something to do with the power of the 3.7 vs. the 4.7 or Hemi?

You are correct about the power, the 3.7 doesnt have any torque at low rpm's.

kjrenegade · **Posted:** Fri Feb 10, 2006 7:36 pm

alljeep wrote:

I know for the CRD we got the 5-45RFE because the diesel is only effective in a very limited rpm range. The extra gear helps us keep in the sweet spot of 1600rpm to 2000rpm better for normal driving.

Yeah, that must be it.. I don't think 1600-2000rpms would be considered the 3.7s "sweet spot" :roll:

ManicMechanicJoe · **Posted:** Fri Feb 10, 2006 8:09 pm

then it would seem to me that we would want a granny gear or something lower then first (say 4:1 giving us a crawl ratio of 40.5 versus 30). More gears and lower gears can over come anything.

kjrenegade · **Posted:** Mon Feb 13, 2006 10:40 am

Adding the 2nd OD gear, and changing the diff gearing to 4.10 would be a pretty sweet combo IMHO.

ManicMechanicJoe · **Posted:** Mon Feb 13, 2006 11:36 am

a second overdrive would be nice (maybe an extra mile per gallon or two) but I want a lower then first gear with a 4.10 in the diffs. a 4:1 first gear with a 4:1 low range in the transfer case would give us a crawl ratio of 65.6... or double what we got right now.

LibertyCRD · **Posted:** Mon Feb 13, 2006 11:43 am

I had the 545RFE in my Dodge Ram V8, and now I have it with the CRD in this Jeep. I HATED this tranny behind the gas engine. It was terrible. Two overdrive gears = worthless! The truck would have to downshift just to drive up a small hill! It got so annoying having to go into and out of the throttle just to maintain a constant speed. With the CRD it's not quite as bad because the torque peak is at 1,800 where it belongs. But it is still noticeable. I would take a good 4-speed automatic (with 4th being the only overdrive gear) over a 5-speed any day of the week. I had a 5-speed auto. in the Ford Ranger I had back in '03 and I hated it too. In theory it more gears seems like a good idea, but in the real world it's not. 5-speeds hasn't helped fuel economy numbers one bit, and it's harder to drive. Just my opinion.

Good news for 5-45RFE and 45rfe owners

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