After a lot of reading about doing a TCM swap with a grand cherokee to get the extrs overdrive gear I finally went ahead and did it. Today I went to a junk yard and picked up a TCM out of a 2002 grand cherokee with the 4.7 and put it in my truck. It only took 10 minutes and I did it in the parking lot of the junk yard. I saw a difference as soon as I started driving it. The truck likes to hold onto the lower gears for a bit longer and rev up a bit but once I turn off OD and it locks the TC it holds the lock a lot better going up hills and accelerating. With OD on the TC wont lock up until about 55 mph but when I does I know Im in the 2nd OD gear and it holds the gear good, not noticably better than before but it did bring my rpms down by about 300 on the highway and I saw an instant improvement in the overhead display. Ive been thinking about it for a while but finally went ahead and did it because Im going up north a few hundred miles for memorial day so its a good time to save on gas with all the highway miles. It was beyond easy and well worth it, if you guys need anymore info let me know. As a side note my trucks at the shop waiting to go in for new bearings and seals in the diff and a detroit truetrac, gonna be an interesting weekend with all the new goodies on the truck.

 

As much as I hate to admit that I'm wrong, there might actually be something to this.

 

The dakota and durango guys have been doing this for years as well as some ram owners. From what I saw, I was always under the impression that the TCM had to be reprogrammed to use in a ram, but today I found differently. I just plugged in the new TCM and drove 50 miles right after, no check engine lights, no rough shifts, just my truck driving the way it should have from the factory. Although I do wish they programmed it to lock the torque converter more, like in 3rd and 4th gear without turning OD off, but I guess you cant always have it all.

 

Cool! is there a specific part number for this TCM? There are a bunch available for different years, etc...

 

I got mine from a 2002 grand cherokee 4.7, an earlier year may work but you wont see a difference unless its been updated with the new 545RFE software. In a write up on another forum the guy used one out of a 2001 and had it updated, but this one was plug and play. The part number is 56041905AD, I found mine on car-part.com. Just enter the car as a 2002 grand cherokee and for the part name scroll down to transmission computer, most junk yards have em for about $50.

 

So far everyone I've seen who's done it has been happy about it. And why not? An extra OD gear always comes in handy, especially if you change the gears.

 

I found something on DT about the guy getting 2.8 mpg increase with the Jeep PCM.


I am still trying to convince my dad he needs it.

 

For $50 and only a few minutes to install its hard to go wrong. I wish I woulda done it sooner with all the drives between home and college 2 hours away, it probably woulda paid for it self in gas savings already.

 

If I had ended up with an 02 4.7 it probably would've been one of the first (maybe top 5) mods I did to it.

 

Made the swap yesterday and drove about 110 miles after. I believe the 3 mpg increase. Also made a huge difference during transmission shifting from all gears. Feels way more solid shifting wise. Went to the salvage yard and got a TCM off a 2002 Jeep GC. No cel light. Thanks for the tip!