4 Hi Blinking Light Fix

I purchased my 2020 CM 1794 used with about 40,000 miles on the clock. When I purchased the truck, the 4WD worked & I tried to engage it as often as I can but not as much as the manual recommends. I am in Louisiana and we had a snow storm that is new to us & when I tried to engage 4WD then the 4 HI light would just blink. I thought it may have been a fluke and moved on. Then I was off road doing some work & ended up getting stuck because the 4WD would not engaged. This motivated me to get it fixed ASAP. I started by applying the parking brake & engaged 4HI with the truck in neutral & confirmed the TC shaft was engaged because it would not turn by hand. If the 4WD was not engaged, it would spin freely & this confirmed the TC actuator was working. I then narrowed it down to the ADD actuator because all other components looked good. Order a new OEM ADD actuator from Ebay for $180 delivered and swapped it. The part was not hard to change & I used hi-temp silicone on the new actuator. I did hand tighten the bolts & waited an hour before fully tighten them to get a good seal. I only waited about 4 hours before refilling the diff fluid. I now have my 4WD back and the problem was the motor on the actuator was seized from rust. The vent tube was in great condition so not sure how moisture was able to get in the motor. Maybe the Louisiana humidity had some part of it. I also went back with Valvoline synthetic

$39 75W-90 GL-5 Limited Slip, Ultra Long Drain 500k Miles, Manual Transmission, Gear/Differential Lubricant (1 Gallon)

75W-90 gear oil.

I wanted to share my experience to potentially help someone that may be having the 4 Hi blinking when trying to engage 4WD.