First off, this is the best, most informable thread I have come across yet after 3 years of searching. Im still not 100% understanding my situation and what is wrong or what steps I need to take to fix my issue.

I have a 2006 Chrysler 300 (base) had the 2.7 w/4speed trans in it. I recently picked up a 3.5l w/ 5speed trans and the PCM / ECU (whatever it is on the passenger side under the vent )out of a 2007 300 Limited.

I installed the motor, not the trans nor the pcm. I know one problem is that I do not recall the year of the vehicle (magnum) I got the harness from BUT aside from the crankshaft sensor pigtail having to be switched with the one from my stock harness, everything else was simple plugin.
The problem I am having is im stuck with reverse and 2nd gear only.

Although I stated that this is the informable thread I have come across, Im so aggravated with the whole thing and my nerves are shot, Im not 100% certain Im reading these posts correctly but it sounds like im kinda screwed here right? Why dont I have all 4 gears?

 

1If it is in fact a 2007 harness, that's your problem. 2007 is its own year of harness and other things. It is a unicorn year.
The reason it only has reverse and 2nd gear is that it is locked in Limp Mode. This means the transmission side of the computer is not seeing a signal correctly. 2005-2006 have to use the respective year harness. If you had to swap crankshaft sensor plugs, you have the wrong year harness. 2005-2006 are their own engines too. They use larger camshaft and crankshaft sensors and you can't swap them out to the 2007+ sensors. The front cover is different and the block is different for the AC compressor rear mounting hole.
2006 had 2 different 4 speed transmissions. This is probably your problem. The first 1/2 of 2006, they experimented with what is called a VLP(variable line pressure) solenoid in the transmission. Then for the last 1/2, they discontinued it. VLP transmissions have an extra plug on the drivers side of the transmission. It is a brown plug with like 7 wires in it. It sounds like you have the VLP transmission and computer but a non-VLP wiring harness. This will for sure lock you in Limp Mode. You need the 2006 harness for a 3.5l with a VLP transmission. And that is almost impossible to find if not impossible. You may have to make one by adding the VLP wiring to your harness. And that can be a trick to do to.
VLP transmissions have an internal counter that counts 2-3 shifts. You get 1000 shifts or 2000 miles before it locks it into Limp Mode. Usually in BFE nowhere in the dark 100 miles from home. The only way to get it out is with a high end scanner that has a reset function for the counter. You can put a 100 transmission in that car and they will all do the same thing until you reset the computer counter. Disconnecting the battery won't reset it either.

 

I’ve almost completed a swap of a 3.5L HO V6 out of an 08’ Chrysler 300 limited into a 08’ Dodge magnum that came with the 2.7 boat anchor. Last thing holding me up is the wiring for the SRV valve. (5 wire valve for 08-10’ model years) Ran all the wires dictated by the diagram and I have 5V constant on my signal wire to the SRV plugged in or not and it is one wire ran directly from pin 21 on C1 connector at PCM to pin 5 at the SRV connector. My sensor ground, 5v supply, SRV control circuit, and ASD relay connections are good and there’s no cuts, scrapes, dings, or dents in any of the wires to cause a short and I believe the 5V should be drawn down by the ground when it’s all connected and running but it is not. Just 5v all the time confirmed on a scan tool. The voltage also doesn’t change when turning the valve by hand (valve disconnected but wires plugged in). What am I missing??? Any thoughts would be appreciated!

 

Not sure which wiring harness you used, that is pretty critical. If you used the correct one, you shouldn't have had to run wires. So, that makes me question a lot of things.
The 5v supply should be on Pin#6. It is not the "signal" wire. Pin#5 is the "signal" wire. Pin#1 is the control wire. If these are not connected correctly, you will have problems. Wiring on some years was kind of weird. The wires don't run directly from the SRV to the computer plug. There is another connector, C100, that 2 of the wires run through. Then to the C1 connector. I had to add the 2 wires directly from C100 to C1 because the 2.7l didn't use them. I attached plug views and diagrams. loop

 

This is an excellent thread, and should be "a sticky" on the main page. Along with it, the thread that discusses how the often forgotten 4.0L engine can be easily swapped in place of the 3.5L when things go awry there.
It's a win-win, since the pricing on the 4.0 is less than the 3.5L (less demand), and you pick up just a little scoot with that extra half a liter.

My proverbial hat is off to you gentlemen for taking on such a project. Those of us old enough to remember the "old" days when you could swap in a small block V8 in place of an inline 6, or a larger cube V8 in place of a smaller one without all of this computer/harness nonsense.

Back in the mid 80's, my friend had a really clean '79 or '80 Firebird Esprit with the dependable but power lacking 301 engine. It would run 100 mph all day long, but took forever to get there.

We found a Pontiac 400 out of a '72 Grand Prix, took it down to the bare block, added lots of go fast parts, and it went right in. The immediate difference was fantastic, but it lacked giddy up off of the line. Once we figured out that the rear end was a tree tall 2.41, we located a 3.23 posi rear end, and man what a difference. It went from being floored and taking off, to wheel spin and a bit less throttle on those hard take offs.

Don