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90grandoneer 06-25-2020 03:19 PM

2008 PCM/TCM in a 2006 Hemi Jeep
It's time to tinker and experiment, AGAIN!!!

I've been thinking about seeing whether a 2007-2008 PCM/TCM will work in a 2005-2006 Jeep ever since I bought my HP Tuner (HPT) and found out they didn't cover the transmission programming on the early ones. The 07-08's have a faster bus controller (NGC4 instead of an NGC3) than the early ones, and my guess is that's why the HPT folks never tackled adding it. The main thing I want to change is the transmission programming...up/down shift schedules, torque management settings, torque converter slip settings and, thanks to caulk04, I've found out that I may also be able to change the 5 speed 545RFE into a 68RFE with 6 forward speeds.....which, basically would just give me access to 2P in the early transmission.

Caulk04 recently picked up an HP Tuner for use on his 2008 WK Hemi and has been able to make some significant progress on reaching these goals. He has provided me with the PCM/TCM part number off the one in his vehicle and I have ordered a couple used ones so I can try several different approaches and experiments.....IF THEY WILL WORK. All of the wiring appears to be the same according to the FSM, the PCM plugs are all the same, the mounts are the same so, it appears that all that needs to be done is install the 08 unit, change the VIN and PCM mileage and see what happens. Sounds easy enough but, I'll be surprised if it really is.

This morning I received my first 08 PCM/TCM and, after disconnecting the negative battery cable and letting it sit for an hour or so to insure all the capacitors in the system have discharged, and then also disconnected the ABS "CAB" electrical plug, I installed the 08 unit into my 06. Tomorrow morning when it is a little cooler in the garage (it's about 95* in there right now and still getting hotter), I'll go and program my 06's VIN and mileage (if my scanner will allow me to do it) and see if my HPT can read the TCM portion of the PCM/TCM. If it does and all else appears to be in good order, I'll try to start it up and see what happens. I think, before I do that though, I'll make sure all my accessories and other components work properly......just in case ?????? If all is good, I can start programming.

I should be able to know one way or another by tomorrow afternoon, or Saturday at the latest, as long as I can program the VIN/mileage. If it does work, using my relatively good diagnostic scanner, I'll shut off some functions I don't like and see if I can add the Daytime Running Lights. With the stock PCM/TCM, my scanner goes through the motions and then says, "Wrong Country Code". It also says that once you change the Country Code, you can't change it back, so on this PCM/TCM I really won't care, because I think I can either work around it or, if not, put the other 08 PCM/TCM in when I get it.

Got my fingers crossed.

caulk04 06-25-2020 03:55 PM

I think you'll just love having access to the 2P gear, especially as a normal component of upshifts. I really hope it works out.

90grandoneer 06-25-2020 06:59 PM


Originally Posted by caulk04 (Post 41003697)
I think you'll just love having access to the 2P gear, especially as a normal component of upshifts. I really hope it works out.

I was re-reading that you said your shifter readout on the dash now says, 1-6. Does it normally go through all gears on normal up shifts or only when you up shift manually? What is the shift pattern when in Drive? If this works, I'll be one happy dude. Then I'd have to start programming up/down shift schedules, WOT shift points, torque management setting, and then start fooling around with the converter slip. I hope I can make them as good as they are with the factory PCM/TCM. I also hope that setting the torque converter slip is as easy as it was with my LX's.

I feel like getting up in the middle of the night after the garage cools off and start messing with it.

Thanks again for your help with this. If you hadn't got your HPT and started fooling around with it, I'd probably still be procrastinating on this mod.

caulk04 06-25-2020 07:25 PM

Before I had the hpt, my display would go 1-5 but it counted funny. 3 was actually 2p, 3 was actually 4, 4 was 5 and 5 was 4. Had to go back to D to have 5th gear.

Now with the hpt and the 2p enable switch on, the display gives me 1-6 and it uses 2p as a normal upshift in 'D'. Before I could only get 2p with the autostick or on programmed downshifts.

What I find funny is that the 08-10 trans operates exactly as the '65RFE' as it was called in newer versions. They also come factory with the '2-3' shift switch disabled. Literally the only difference is they stopped using the 2p name and renumbered the gears.

Something non-trans related that I 'fixed' recently was the big flare and high idle at start-up. I see the idle max setpoint to 800 and as soon as it fires it drops down instead of hovering at 1200 or whatever.

jeepjeepster 06-26-2020 06:05 AM

Do you think the high idle is to help pump oil through the engine when its cold? Or just to help it warm up? I've personally never liked the high idle at startup but my two ZJ's dont do that. I've got a honda accord that stays at 1200 forever.

caulk04 06-26-2020 08:03 AM

I'm fairly certain it's an emissions thing. Warm the engine and cats faster.

Rtbrjason 06-26-2020 02:45 PM


Originally Posted by caulk04 (Post 41003889)
Now with the hpt and the 2p enable switch on, the display gives me 1-6 and it uses 2p as a normal upshift in 'D'. Before I could only get 2p with the autostick or on programmed downshifts.

Is this option available by default?

caulk04 06-26-2020 04:47 PM


Originally Posted by Rtbrjason (Post 41004607)

Originally Posted by caulk04 (Post 41003889)
Now with the hpt and the 2p enable switch on, the display gives me 1-6 and it uses 2p as a normal upshift in 'D'. Before I could only get 2p with the autostick or on programmed downshifts.

Is this option available by default?

With HP tuners? Yes. It's right there in the trans settings, but only NGC4 controllers (07+).

90grandoneer 06-26-2020 05:08 PM

OK gang, IT WORKS, and now it's just clean up loose ends and start programming with the Diablosport (DS) and HP Tuners (HPT). If anyone wants to do this the "easy" way, you'll need to have a relatively high end diagnostic scanner with the capability to reprogram the VIN number and PCM odometer into the 07-08 PCM/TCM. Otherwise you''ll have to send it off to have someone do it....usually costs about $75-125 or so.

Some observations about the STOCK differences between the 06 and 08 programming:
--Initial cold start RPM with the 08 unit is way too high.
--My scanner (Autel MS906BT) can't find the transmission in the 08 unit, but does with the 06 unit. My HP Tuner doesn't have a problem finding it though...YAY!!!! I am thinking that on the 08, they combined them into one unit and cover both engine and transmission under the heading, "PCM", even though both the PCM and TCM are separate units within the PCM.
--My DashHawk now shows quite a few N/A's that used to work fine with the 06 PCM. I am figuring this is just a re-programming issue on the DashHawk. We'll see.
--The shift schedules on the 08 unit are somewhat better than the stock ones on the 06 unit, but still no where near the way I want them.
--The engine tune on both the 06 and 08 units really sucks when applied to my pretty well modified 5.7 Hemi. I'll bet it's down at least 50-75 horsepower.
--The WOT throttle up shifts are set at 5600 RPM with the rev. limiter set at 6000 RPM on the 08 unit....I don't remember what they were when stock on the 06 unit.

A few other things to note are that, if you do this change, you'll get a whole load of DTC's at first and most will be easily resolved. None stopped the vehicle from working as good as it could with the stock 08 PCM/TCM. The software version (Calibration Files) on the 08 NGC4 unit appear to be the latest available (05187360AI) which is a good thing. I've done fairly extensive modifying to the up/down shift schedules, torque management and torque converter slip %ages on both of my Hemi LX's, and the similar settings for the 545RFE are quite a bit different on the HPT and will probably require a learning curve or more picking of caulk04's brain.

caulk04 06-26-2020 05:57 PM

Awesome, so happy it works.

The RFE is setup far differently in as far as the tables you see. I've looked at nag1 tune files...

Sadly I think you'll be disappointed with the options for the converter compared to your nag1 vehicles, but that's just nitpicking.

mrgc2 06-26-2020 07:30 PM

Whatís the benefits of changing it to 6 speed, I have a 10 overland, any extra power or fuel economy Iím all ears I also tow a 2500kg boat on long journeys.

Sent from my iPhone using Tapatalk

caulk04 06-26-2020 08:58 PM

You can already access the 2p gear with your shifter as I've described above. You would only need to purchase HPtuners (or buy credits for someone with the hardware) to activate the 2-2p switch.

What's going on here is basically guys just playing around and adjusting things to their exact liking.

90grandoneer 06-27-2020 09:19 AM


Originally Posted by mrgc2 (Post 41004803)
What’s the benefits of changing it to 6 speed, I have a 10 overland, any extra power or fuel economy I’m all ears I also tow a 2500kg boat on long journeys.

Sent from my iPhone using Tapatalk

My guess it that you don't need it, as you already have the capability to access 2P (the sixth gear). I would think yours is very similar to caulk04's. He can probably give you a little more info. on this.

90grandoneer 06-27-2020 06:07 PM

Yes, the NAG1 was fairly straight forward and somewhat easy to work with, although getting everything to work the way I want is the problem. I've got those pretty well set now, but not what I'd call perfect for my nit picky desires.

I haven't sat down and looked at much of it yet but, can you start me with the 6 speed setup? Aside from this one change, I think I'll pretty much drive it this way until I start figuring some of it out. I may also stick my old engine tune on it. The HPT should easily be able to do that, as the only files I have for the 06 PCM are the engine files since the transmission wasn't covered.

90grandoneer 06-27-2020 06:56 PM

My "fun meter" is just about pegged out now from messing with this. I started this morning by making a little checklist on things I needed to do and the order I wanted to do them. I started by adding a modified DS 93 tune which will be what I start with when tuning the engine and transmission with the HPT. I did this with my two LX's and it seemed to work well to use the DS tunes as building blocks.

I also had a B233D Occupant Classification System (OCS) Code that I screwed up and caused right after I installed the 2008 PCM/TCM and was "clearing the codes." I didn't read my scanner correctly (duh!!) and tried to recalibrate the passenger seat weight sensor without reading how to do it. Because of this, the passenger side air bag wouldn't work when someone was sitting in that seat. I spent about 3-4 hours messing with this, as the FSM was almost totally useless.....needed to know the weight of a car seat, and the weight of an average six year old child. Of course, the FSM doesn't tell you how much weight that is.....just use their OCS weight set to do it. After trying, unsuccessfully, to wing it for a while by 'guestimating" the different weights, I finally got on the internet and found out an average 6 year old should weigh......about 45 lbs. Weights needed to be within 5%ile. I ended up putting a bathroom scale on the seat and put about 10-15 lbs. (using my hand) on it to simulate the weight of the car seat. The scanner went through the first 3 steps OK and then it was time to "put the kid in the seat". Using my hands, I pushed on the scale up to 60 lbs. (weight of kid and car seat combined) and it finally passed and recalibrated the seat weight sensor and turned off the DTC.

Next, with the HPT, I was going to make a copy the modified DS tune (engine and transmission) so I could go back to it if I ever needed to start over. This went well. Then I was going to enable the 2-2P switch so I would have the 6th speed. Apparently the HPT didn't like the fact that I changed the PCM/TCM and wouldn't let me load it. It wanted me to buy more credits so I could use these new files. So, I could read the vehicle, edit the files, but not install them. This is where I stooped messing with it and will get on the HPT website and find out why a vehicle that is properly licensed can't install files after a new PCM/TCM has been installed. Worst case scenario is that I'll have to use my last two credits to be able to do this.

My last thing for the day was to do a little re-programming of my DashHawk because on 4 different screens I had one or more items that no longer worked after installing the 2008 PCM/TCM....oil pressure, both engine banks' knock retard, transmission fluid temperature (never was accurate but a good reference), and turbine in and turbine out speeds. I tried numerous different PID's to no avail and ended up inserting items that would work.

I am done for the weekend and will probably just drive it for a while and start making notes of the things that I don't think are quite right or the way I want them, mainly up and down shift schedules, torque management settings, WOT shift points, and cold start fast idle. I think, after all is said and done, I'll end up being happy with the way things will work.

The time now is 10:41 PM.

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