80% of the time when shifting from reverse it jumps into limp mode?

Can we run the codes to see what comes up? Here are a couple of guides to help us get the codes. You can get a CAN scanner (Controller Area Network) from Amazon. here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is a list of CAN scanners starting at about $25.00 on Amazon

https://amzn.to/3DBMlc7

It sounds like you have a reverse shift solenoid or transmission control module that is shorted out here is the location of the module so you can check it out. Check out the images (below). Please let us know what you find.