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

[Jeepguy43]

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 03 Dakota CrewCab 4.7 all that had the 45 or 545RFE ******. I've plowed commercially with both the Ram 2500 and Dakota putting this ****** through it paces. I never once had a problem with it and know for a fact that its built for a much heavier, larger, and powerful vehicle.

Downsides- I hate the gear spacing when placed in a Dakota/Ram and the programming leaves much to be desired.

Anyways, I belong to other forums for the trucks and back in 2007ish guys were realizing that you could Flash the TCM of trucks to make the 45RFE to have the second overdrive of the 545RFE lowering highway RPM's by about 300RPM. Guys with Ram's and Dakota's were netting 2-3mpg on the highway with this mod. When I realized that the Liberty had this ****** I knew it could be done.

Thankfully my company is licensed by GM/Chrysler/Ford to do warranty work on our fleet meaning I have access to all factory flashes and TSB's, etc. Here is what I found - TSB# 18-025-01

"THIS REVISION TO THE TCM SOFTWARE ADDRESSES THE ABOVE SHIFT QUALITY CONDITIONS FOR ALL VEHICLES AND ADDS A FINAL GEAR RATIO TO THE 99 & 2000 GRAND CHEROKEE TRANSMISSION ONLY"

Fact is, they all use the same TCM. After 2003 the transmission programming was integrated with the ECM, any years before that using the 45RFE ****** can have this flash done.

I plan on bringing my Jeep in this week to work and flashing the programming in.

Just throught I'd post this info up in case you guys weren't aware of this. I know that my Jeep will benefit from this as a lot of our roads are long and higher speed (55mph speed limits).

 

[tjkj2002]

You still stuck in the '70's? The speeds limits have been much higher then 55mph for decades and going higher soon.

That 2nd OD is a bit much for the 3.7 to handle,puts the rpm's to low and the engine lugs getting worse mpg's.Just because your turning higher rpm's does not mean your using more fuel then running the same speed at a lower engine rpm.

 

[Jeepguy43]

You still stuck in the '70's? The speeds limits have been much higher then 55mph for decades and going higher soon.

That 2nd OD is a bit much for the 3.7 to handle,puts the rpm's to low and the engine lugs getting worse mpg's.Just because your turning higher rpm's does not mean your using more fuel then running the same speed at a lower engine rpm.

I meant our back roads are higher speed roads than a normal 30-40mph Roadway. Most of the roads up here are 50mph or higher.

I understand the difference between lower (numerically) gearing vs the engines efficient range of RPM's which is why I get annoyed when magazines keep talking about 3.55 gears or lower as the best way to get mpg's. Regardless, at 60-70mph my liberty is turning I believe at or above 2000 RPM's, dropping that by 300RPM's will not lug this engine and I believe it will turn better mpg's overall.

 

[tommudd]

dropping it to 1700 I would say will in fact start to lug it. You would notice a huge difference just from experience. Same as installing taller tires, mine was a complete dog at 55 with 32 inch tires, couldn't even run overdrive at that speed

 

[tjkj2002]

I meant our back roads are higher speed roads than a normal 30-40mph Roadway. Most of the roads up here are 50mph or higher.

I understand the difference between lower (numerically) gearing vs the engines efficient range of RPM's which is why I get annoyed when magazines keep talking about 3.55 gears or lower as the best way to get mpg's. Regardless, at 60-70mph my liberty is turning I believe at or above 2000 RPM's, dropping that by 300RPM's will not lug this engine and I believe it will turn better mpg's overall.

It will lug big time.With the 3.7 you want your engine turning as close to the torque peak as possible for best power and mpg's,which is 4200rpm's.The 3.7 needs higher rpm's to return the best mpg's as it's trying to move a 4000lbs brick.

My best highway mpg's are when the engine is turning about 2800-3000 rpm's.Gets way worse mpg's dropping down to 2000-2400rpm's,even as low as 2600rpm's, as it is constantly hunting for the correct gear ratio.

 

[Jeepguy43]

I guess we will see. If it doesn't work, I'll just re-flash it again. I will let you guys know how it turns out, I'm planning on bringing it in tomorrow.

 

[tommudd]

:shrug:

 

[wmcreyno]

Hey guys, I have a quick question. I have a 2002 Liberty with a 2.5 inch Ome lift and 245-75-r16s on it. I have had a 2004 Grand Cherokee TCM in my liberty for a while. But I just recently did the lift and tires. Is this transmission controller actually enabling the 5th gear ratio? Or is it just changing the shift points line pressures and torque converter lock up? Is this going to hurt my transmission in any way? And will this Grand cherokee provide any benefit to fuel economy or the vehicle with the new lift and tires? Or should i just go back to the old factory liberty TCM? And finally i did the Torque management wire snip. Is that hurting my transmission?

I am somewhat new to modifying KJ'S your help is greatly appreciated!!!!

 

[Ranger1]

It's been tested by a few over the years, using newer TCM's with 5th enabled in older 45RFE vehicles. The TCM's for the 45/545RFE are basically the same hardware, with several versions of software over the years. Some have tried taking the TCM from a 545RFE Grand Cherokee and installing it in 45RFE equipped Liberty's only to find that 5th gear (.67) OD did not activate.

I've personally installed a 2005 Liberty CRD 545RFE 5 speed TCM in my 02 Liberty and found the same result. No 5th gear and increases sloppiness in shift quality over the 02 Liberty code. I found a hint as to why in an old DC transmission training manual (that I no longer have). The ECM to TCM communications on startup includes an interrogation message by the TCM to the ECM, to determine the vehicle model it's in. The TCM has more than one set of shift maps installed, so they say in the training course. When it derives the vehicle type (from the VIN IIRC), it uses the correct shift map for that vehicle. This enabled the same basic hardware in a range of model years to be used for the same transmission in Jeeps, Dodges and possibly other 545RFE equipped models.

The training course details how the correct shift map is derived by the TCM once it "knows" which vehicle it's in, not whether the 2nd OD is enabled or not.

This seems to be because the same 2005 CRD 545RFE 5 speed TCM only uses 4 speeds in my 02 45RFE. It apparently worked on the 99-2000 models of Jeeps and some Dodges when fitted with a newer software TCM because the VIN range fit the newer maps that were supplied with the TCM's sometime in 2001.

I know of one case where a CRD owner tested a Dodge 545RFE TCM in his vehicle and found that the 5th gear was still enabled, but the shift points were at lower rpm's on some gears. Clearly, if the TCM programming doesn't have a later model VIN range to match with, it still uses a set of shift maps.

I'm guessing that it's possible that if you found an older TCM(circa 2001) with 5th gear enabled, it might not have the VIN range for the Liberty in it and may default to something other than what the 2002 and early 03 Liberty's used.

It would cut down the range of TCM's to look at because if the training manual is correct, if the software knows the 2002-03 Liberty 45RFE VIN range, it's going to use the correct shift maps for the 45RFE.

 

[rockymountain]

What would a 545RFE program do anyway actually. Its not like it would just simply add a 5th gear and if it did then you would be wasting your time. It would suck on the highway with the same gearing and everything. There's a lot more to it than that I believe. This would have to "spread" out the gears not just add one. All the shift points would change and you would then end up with nearly the same rpm at highway speed. Each gear would just be a little lower and shorter simply speaking. That's where you make up MPG, not just cruising on the highway. The more gears you have the easier it is to put the engine in the most efficient rpm range.
That said simply "adding" a 5th gear would be the same as putting on bigger tires. On the highway it would suck.

 

[warp2diesel]

2003 5.7L Hemi Dodge Ram 1500 TCM in '06 CRD

Ranger1 provided me with the master list of TCMs and PCMs and I plowed through it, then I read a lot of posts on TCM swaps. My 2003 5.7L Hemi Dodge Ram 1500 TCM took a lot of time to train in the slow learn mode to get where it is today. Since the CRD with an Inmotion Stage II tune has lots of torque it works well and there are only two things I have to do to make it work well: 1) Do not floor the accelerator, just press it down so it does not rev over 3,800 RPM and I can blow away Tahos and most other Gasser SUVs. 2) Turn off the OD when I tow 5000# to 7000# when driving under 60MPH.
Does the CRD engine lug, only if I tow 5000#-7000# under 60MPH with out shutting off the overdrive. Under normal or lighter towing, it never lugs.
Suncoast/BG-Chrysler experimented in flashing 545RFE transmissions to make them into a 6 speed and the only truck that got it to the best of my knowledge was Chris Wolverton's (Ron's son). It took 2nd and 2nd' and made them into two separate gears. One day Chris loved it and the next day he hated it. On the 68RFE transmissions that are 6 speed units, the owners hated the close gears and as part of the Suncoast/BG Chrysler Stage 2 TCM tune for the Dodge Cummins Rams with the 68RFE, they made it back into a 5 speed to make better use of the torque the modified Cummins put out.

When I had the time and shop facilities to play around with engines more than now. I would connect a Knock sensor screwed into a piece of 1/4" X 1" bar stock 6" long and clamp it onto the engine lifting eye with a pair of Vise Grips. Connect 1 wire to the Piezo Electric Knock Sensor and one to ground, run wires into the cabin to my volt meter and set it to the lowest voltage setting. If the engine lugged or detonated the Piezo Electric Knock Sensor would put out a ~0.5 Volt signal. The Knock sensor was off a Mid '80s Labaron Turbo, other Knock sensors will work.
Another way to check for lugging is to connect a vacuum gauge to the intake manifold. With the old Carb engines anything under 10" was lugging unless you were under hard acceleration, with fuel injected engines they can be run below 10" of vacuum with out problems, i would draw the line at 8" of vacuum for steady highway cursing and use the Knock Sensor to verify there is no detonation.
Now you all know my tricks I used to analyze gearing options and ignition timing. One could go for what is best for the engine, not some EPA officials regulations.

If you want to cough up the $1,000 plus in cash, Dave at BG Chrysler will be happy to develop the flash to make the early 545RFE transmissions that are TCM neutered into a real 545RFE. Ranger1's idea of trying an earlier TCM that predates the Liberty 3.7L would be a more economical option. All you need to do is a lot of research and wait for someone with the right GC to get drunk, drive, and get into a wreak.
I was able to do the TCM transplant, and now it works. But like a teenager, it takes some time a patience.