Okay so I understand that I can either get my TCM reflashed and make my 4spd a 5spd or upgrade the TCM with a 2003 545RFE and get 5 gears.

 

not quite

in late 2002 and 2003 MY trucks the TCM and PCM was put into ONE UNIT, for example (ill try and take pictures tomorrow) my 2002 had i believe 4 plugs on the PCM and no separate TCM module(earlier MYs have a 3 plug PCM and a separate TCM). I have heard of people swapping TCMs from jeeps w/ the 4.7 and 545 in order to get the 5th speed to function, these can be pulled out of junkyards or find a vin in a junkyard and go to a dealer to get the module.

 

Since I changed my spark plugs i've been getting about 18mpg highway and 15 city. I'd just love an extra gear to drop my O/D down from 2k RPM at 65 mph. I might even be able to manage 20mpg if i could use my Cruise Control. If I had a 5th maybe even a 23mpg.

 

you probably wont get over 20 my best ever mpg read out using OD and cruise was 19.85 mixed driving (30% city, 70% highway) so i was doing over 20-21 on the highway because i was getting 17-18 around town at that point, be happy i fyou can get it up to 20, also i can cruise at 75-80 turning 2k rmps

 

So youre saying that all I need to do is go to a junkyArd and find a PCM to a jeep with the 4.7L/545 and swap it out with mine and I should get a 5th? Sorry to sound so ignorant on the topic, but transmissions aren't my specialty.

 

that is what i have heard yes will it actually work? i see no reason why not, but i havnt tried it myself.

 

This discussion got me to look this all up and see if people have tried it and what they got out of it. It does work if you find the exact TCM that you need. I thought about doing it on mine, but I don't think it would help in stop and go traffic, or with city driving, which is where my gas mileage is really bad. Depending on whats going on, I get about 13-15 MPG on average. One time with a lot more highway driving than normal, I got 17. I know mine gets about 20 ONLY when doing 100% highway driving, and thats only when the cruise control is on, I don't have a steady enough foot. When I'm going about 75 the engine is going about 2200, I think, and about 17-1800 maybe at 65. I'll have to look more closely. I know at 45 its not too much above 1400. My Neon had the engine going about 3200 at 85, but that was a tiny I4 engine, not a V8

And if you do decide to buy a TCM (new or used) this is the one you need: RL041504AG Its out of a 2001-02 Grand Cherokee, and apparently the letters on the end make a difference, it has to be the AG. And a 2003 Durango PCM won't fit, yours (and mine) uses a separate ECM and TCM, rather than a 1 unit PCM, which makes all the wiring different.

 

Do you have a link to where I could go to get one? just tried to fine a TCM on a jeep wepsite and none of the years (01-03) even show they had a 545RFE. I want a 5th more or less for when I drive to Lincoln Ne at 80-85 MPH. If I could get the RPMs lower it would help a lot.

 

That I don't have, chances are you'll have to check with some junk yards, maybe if there's a place around there that sells used parts, or the dealer if you want to pay for a new one.

Speaking of Lincoln, I'm going to end up out there a week from today. We're taking the LONG way to Kansas City because my friends thats going with me has to stop in Omaha to pick some stuff up.

 

Very nice, I live in Omaha. have found that I need part# 56041905ad from a 2002 grand cherokee 4.7. A local junkyard can get me one for $100. I'm just worried (like I was with my T/S lift) that things wont come together like I want them to. I'll go check my Trans code and my TCM just to make sure everything will fit properly.