Electrical 2008 GT Automatic to Manual Swap - No Crank


New Member
Mar 14, 2022
Hello all,

I have a 2008 Mustang GT that I've swapped a TR3650 manual transmission into following this guide: https://www.stangnet.com/mustang-forums/threads/auto-to-manual-trans-how-to-guide.783401/

Before putting everything back together, I decided to try starting it up. It started just fine with the automatic computer. I then swapped the manual computer into the car, which came from a 2007 manual GT and programmed new keys using Forscan. Forscan told me it was successful and that two keys were programmed now. All of the lights come on with the keys and everything works, except for when you go to start the car. It does not even attempt to crank. The PATS light is not flashing with the keys I just programmed, so it seems programming was successful. I inserted an unprogrammed key just to verify and the PATS light does flash.

The next thing I did was I double checked my connections at the battery were tight and clean and verified the cables at the starter were also tight and clean. I put a jumper box on the car and tried starting it with no luck. I also put it on a charger overnight and tried the next day with no luck. I took the starter off and jumped it and it does in fact work. I just wanted to make sure that it didn't just happen to go out. I've checked all of my fuses and I've swapped my fuel pump and starter relay with no luck.

I am kind of at a loss here. The only thing I could think of is maybe it's a neutral safety switch thing that I didn't wire up. I followed the wiring in the how-to guide I linked above. I was under the impression that the red/light blue and white/pink wires from the auto transmission harness were the neutral safety. I checked for any wires in the driver foot well by the clutch pedal and the only thing I found was an open plug pointing straight down with three wires on it. I thought maybe this was the neutral safety switch so I cut two of the wires and connected them together. This did not work either. The third wire on that connector was a black wire and I have not touched that one yet. Do the autos have a neutral safety switch harness near the pedals? I cannot find any other empty plugs.

I'm wondering if anyone else has done this swap and has run into a similar issue or knows if there's anything additional I need to do or if anyone has any ideas? I will try to provide as much information as possible and can provide pictures as well.
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Update: I figured it out. in the 07+ it seems you have to jump the neutral safety switch...which is what I thought but I misunderstood and thought the wires from the transmission in the guide were the ones I had to do. I actually had to connect the black and grey/yellow wire from that connector I found underneath the dash. I had not tried the black wire and I should have before posting. This makes sense now why it started with the automatic computer but not the manual computer. Posting this in case someone else has problems in the future.