This is even with the impact driver coupled with the JIS bits?
How was this determined? Battery tester or multi meter or just listening to the sound of it trying to crank over? Have not read through this whole thing so apologies if this was mentioned already.
You might think about getting the battery properly tested and then source a new battery cable set if the original set is still on the truck.
@Fourrunner I believe still makes a nice kit.
The kit costs $155.00 shipped (within US). International shipping is available. The kit includes 5 cables and battery terminal connectors. This kit fits FJ60's and FJ62's. See below for additional kits (FJ40, FJ80 and FZJ80) Kit includes: Battery positive to starter cable (with protective...
forum.ih8mud.com
Made my truck come alive from an electric power standpoint. I use an Optima RedTop from 2016 which has served me well but not sure those are what they used to be nowadays. But I think any Group 27 battery works fine. Folks have had good success with Interstate. HTH.