Speedo correction still in limp mode

[GNiederb]

I have a 2005 Chrysler 300c. I've talked to the tech department already, and the more I dig into my issue, I'm beginning to think the tuning is fine, but my car has its own physical issue, but some symptoms are weird and I wonder if the community might indulge me a second and see if y'all have any ideas on my troubles.

So my rear end diff leaked fluid and ate itself to death. It's a discontinued part, so I found the cheapest thing close to fitting and ended up with a assembly meant for a v6 car, so the ratio is different. Same axels and hubs, all I had changes was the center section. Had to swap pinion flanges but otherwise it fit. So leaving out some irrelevant parts of the story I eventually tried to adjust for the new ratio with the predator 2. The new ratio is 3.90, the tuner allows me to choose 3.92 which is of course close enough. The shifts are smooth but when I hit fourth gear it throws codes and goes into limp mode. Codes for improbable wheel movement, incorrect gear ratio, and generic tcm code. On one test drive my esp light came on. I tried other ratios and the shifting seemed harsher, like it didn't have the right shift points. The part that is weird is that no matter, stock, 3.92, or any other setting, the speedometer is still registering correctly when checked against gps. Also the rpm does match the speed for a 390 ratio.

So doing my research, I'm thinking the shop probably messed up my abs tone rings, they are rubber rings on the axel shafts at the hub, and probably 15 years old, so when they pulled the axels, I bet they got messed up, and could cause those same codes, but the speedo has me weirded out. I wonder if it's possible it reads speed off the tranny but then verifies and corrects from wheel speed, and my front wheel abs speed sensors probably work fine. I also wonder if I disable the abs if I can drive the car home, or if it will still be in limp mode.