'04 5 speed transmission

[glennco1]

2 weeks ago I bought a '04 GC with a 4.7L and the 5 speed transmission 1200 miles. So far I have yet to see a discernable shift into 5th gear. is this normal?

Secondly, when I hit the OD/Off switch the engine goes up to around 3000 when cruising at 70, is this normal?

I started getting concerned when I read in a Dakota message board that the 545RFE transmission is the same as the 4 speed, but with a different software package to enable the 5th gear. Then it occurred to me that when switching out of OD, the system was actually going to 3rd gear instead of 4th.

Does anyone have any experience with this, and understand the workings of this 5 spd at all?

I talked to my dealer, they were no help.

[msrjeep]

OD is like a second gearbox on a transmission. when you have overdrive ON the OD shifts to a taller gear and locks the torque converter to the engine RPM for cruising on highways. that's why you turn off OD for towing. I know the 4 and 5 speed transmissions have an extra gear for better acceleration at high speeds for passing, etc.

[glennco1]

Ok, my owners manual states that 4th and 5th are overdrive gears, which I'm not quite understanding, also I still haven't felt a discernable 5th gear shift.

Any more thoughts?

[xj31]

the ratios are so close that its almost impossible to tell the difference between 4th and 5th.and you are correct,that trans is a 45rfe(4speed) with different software so its now a 545rfe(5speed)the early ones can also be reprogrammed into a 5speed.By the way it also has 2 different 2nd gear ratios.one for upshifts and one for downshifts

[glennco1]

Yeah, I had read somewhere that 4th gear was .75 and 5 was .67. That is so close that I can't imagine it doing much of anything at all. Thanks for confiriming all this for me.

[glennco1]

Another quick follow-up. Are the ratios so close that I won't even feel it kick into 5th?

thanks again

[xj31]

yeah its pretty hard to feel it go into 5th.plus that trans shifts pretty smooth to begin with.Ive driven more than just a few of them,I'm a tech at a jeep dealer.if its broken youll get a check engine light.

[xj31]

also i know this thing is programmed to act a little different until its broken in,like the torque converter clutch is pulse width modulated and it wont fully apply right away im not 100% sure how many miles it takes until it lets it operate normally. im wondering if theres something going on with it not letting it go into fifth until its broken in.i dont have any manuals with me but if i find out next week at work i will post it.

[afgunn]

I realize this post is old but I have some first hand experience having owned a 2005 Dakota and now a 2004 Dakota both with the 545RFE transmission.

First in the 2005 Dakota the button in the end of the shift lever turns on/off the Tow/Haul mode (and the indicator). In the Tow/Haul mode the fifth gear (second OD .67) is locked out and the shift points are higher (firmer?). The difference between 4th (.75) and 5th (.67) is about 200 RMP. It was great driving in town or traffic with Tow/Haul on!

In the 2004 Dakota I have noticed a difference! The button in the end of the shift lever turns on/off the OD (overdrive and the indicator) - BOTH of them! Hence going into 3rd gear (1.0). And yes the RMP jumps about 1000 RPM at highway speeds. After switching off the OD cutout, I see the RPM drop about 800 (4th) and then 200 (5th). Very different operation than the 2005 and later models. And I really like the operation of the 2005!

Does anyone know if/how we might update the 2004 to the 2005 mode?!!! Buy a new TCM maybe?!!!