Problem with choosing the right rear axle ratio

I tried Allison as well and they could not find any issues, they even used one of they’re computer to make sure that the tans was working properly. I guess my issue started when I fist bought the truck. The DPF put the truck in inhibit range due to it being coughed up. I bought a new filter ($1400.00) and installed it the mechanic put the computer did a parked regen (through the computer) and all was well a few days later my transmission warning light would light up “overheating” I right away called Allison and took the truck for an inspection with them they stated that the reason the temp was going up was due to some wires being loose and that was the reason why it was going crazy. Before any of those problem the would drive at about 65mph max (it wouldn’t go over that) once the dpf filter was changed that when I started experiencing all those problems. I’ve been to Allison twice after having the rpm’s go up so high and also Freightliner just to make sure I didn’t need a new tranny or engine (ecm or anything electrical) etc.

 

To be honest I’m not sure but doubt they did since I was there when my mechanic did the parked regen. All he did was resert the fault codes and did a parked regen. At Allison tho they go under the truck and mess with some wires which I was not able to see what they did.

 

I cannot find any tags or plates on the rear of the truck the differential have writing with a marker but hard to read it looks like someone previously changed the rear axle.