We flat tow (on all 4 wheels) a 2019 Ranger 4x4 and recently experienced a transmission failure. It was in tow mode and transmission was in neutral as required by the owners manual. It is being worked on at the Ford service department, but they said something to me that does not make sense. They said that the transmission still gets spun while the transfer case is in neutral. I am hoping someone here can explain That statement. My experience is with mechanical shift transfer cases where neutral means both drive shafts are disconnected from the transmission. Thanks in advance.
Quick review of most transfer case designs currently offered:
input shaft is connected to a set of planetary gears. Inside the input shaft is a pocket bearing.
The output shaft is inserted into pocket bearing.
On the output shaft, there is the pump to ensure everything in lubricated when truck is in motion, the sprocket for the chain which is used to power the front wheels and at every end the splines to connect the u-joint for the rear output shaft.
Over the front of the output shaft is a range gear which engages/disengages the planetary for 4 low. By carefully locating range gear, there is a position which engages neither low nor high range. How the range gear is positioned - electronically or manually is irrelevant.
Now, to the problem:
You will note that the rear output shaft is turning whenever the rear wheels are turning. Which means the shaft is turning in the pocket bearing.
Now, if the oil is thick (cold day), the tolerances of the bearing are a little on small side, the tolerances of the output shaft are a little on large side, the bearing hasn't spun in some time, i.e. you haven't used 4-lo recently*; there will be an amount of rotational force transferred from the output shaft to the input shaft.
The result will be the input shaft is spinning - which as the transmission is in neutral, will allow the transmission output shaft to turn. However, if the engine isn't driving the pump on transmission input shaft, nothing in your expensive automatic is getting lubricated. And after several thousand turns unlubricated bearings stop turning and bad/expensive things happen.
What I don't understand - why Ford is recommending leaving the transmission in neutral. Putting the transmission in Park, locks the rear output of transmission from turning. Without the transmission turning, no damage can occur to transmission. And if transfer case didn't shift into neutral, you
should notice that the wheels on the Ranger aren't turning - so go back and correct the issue.
Note: Jeep requires automatic in Park/manual in 1st.
*If transfer case is always left in high range, as the output and input shafts are always turning the same speed, they will always be in same position. The result is the oil breaks down between bearing and shaft and false brinelling occurs, effectively locking the input and output shafts. This shouldn't be an issue with your 2019, but could be issue on my wife's '02 Explorer Sport which hasn't seen 4-lo in almost 20 years.