2003 jeep liberty 45rfe transmission TCM swap to a 545rfe???

[Kaden5645]

Okay, I'm just curious if anyone has heard or has done this. I heard and read about the 45rfe transmission and the 545rfe transmission being exactly the same besides the programming in the TCM. I've also read and watched some videos on people changing out there TCMs in other jeeps that had 45rfes and turning them into 545rfes. Does anyone know if it's possible to do this with a 03 jeep liberty and if it would make a significant difference regarding MPG and such?

 

[04Liberty]

I know it has been done for fact on older Grand Cherokees and Rams. You are correct, no difference but programming. Theoretically it should be doable (TCM's aren't VIN dependent) but will you actually get any use out of the extra overdrive gear (that's all it does, gives you 5th gear)? I imagine if you spend alot of time on the highway at decent speeds then it might be worth doing.

 

[mercdudecbr600]

Resurrection of this thread for a hot minute because gaining an extra gear when you have a 02-04 KJ + 4.10 gears (seemed) like a decent strategy to upgrade the KJ.

Onto the swap. I put in a 2002 WJ GC TCM PN# 56041905AD (the one every says works on the GC forums) into my 45rfe equipped KJ - I DID NOT GAIN A 5TH GEAR, RPMs were the same at 70mph and I did not detect another "shift". Good news though, this TCM shifted pretty close to the same as before, maybe a little crisper (I also have a shift kit installed). Not a huge investment into it, but a decent experiment.

I know this has been discussed before with some adding that it has do with VIN - the KJ never got the 545rfe - so the TCM won't activate. And this is confirmation of that (sadly).

 

[KJowner]

The CRD's have the 545 with the extra gear so it can be done, no idea how though!
@joshgoble any advise?

 

[mercdudecbr600]

It should be as simple as replacing the TCM, but at this point I’m not convinced it works for a 3.7 kj.

 

[mercdudecbr600]

Flash a 45RFE to a 545RFE- Anyone done it?

So I just found out this past weekend that my 2003 KJ built in May of 2003 actually has a 45RFE ****** (Backwards angled cross member, TCM mounted on passenger fender, 15 bolt ****** pan). I was elated to say the least for many reasons- I've now owned an 02 Ram 1500 4.7, 04 Ram 2500 HEMI, and...

www.jeepkj.com

 

[KJowner]

That explains it

 

[rustydread777]

As far as I've heard, you need to change the solenoid pack to the white plug with the shift selector bracket. The 45rfe and the 545rfe have a different solenoid and shift bracket internally from what I've read. TCM would be the last piece of the mods. Hopefully someone with more knowledge comes in and pays as I'm wanting to do this.

 

[2TALL1]

I’m interested in this and I don’t even have an automatic.
This would be a cool hack.
It’s like the evic install super cool and relatively easy to do.
Or the towing fan shroud and manual fan for cooling.
All great easy to do upgrades.
So definitely someone needs to figure this out or if they already have.
Please share.

 

[04Liberty]

As far as I've heard, you need to change the solenoid pack to the white plug with the shift selector bracket. The 45rfe and the 545rfe have a different solenoid and shift bracket internally from what I've read. TCM would be the last piece of the mods. Hopefully someone with more knowledge comes in and pays as I'm wanting to do this.

The 45 and 545 are the same physical transmission. Even the 65RFE is essentially the same trans but if memory serves they changed the connector (don't quote me). It's the programming that determines how it acts. Someone years ago figured out the RFE is theoretically capable of like 14 fwd gears and 2 reverse. From 1999 til about 2010 RFE's are forwards and backwards compatible and in both 2wd & 4wd versions. Lord knows I did enough of them before finally getting rid of that truck lol.

 

[mercdudecbr600]

I’m interested in this and I don’t even have an automatic.
This would be a cool hack.
It’s like the evic install super cool and relatively easy to do.
Or the towing fan shroud and manual fan for cooling.
All great easy to do upgrades.
So definitely someone needs to figure this out or if they already have.
Please share.

Yeah I already did like 4 posts ago - it doesn’t work.

 

[2TALL1]

Cool I guess I missed that part.
That was great a lot of good info.