If you tow with rear wheels down (turning) you either must disconnect driveshaft or keep the engine running.. otherwise you will destroy tranny.
there is no lube with engine off...
unless you are going a "very" short distance
this is true for gm or ford...
the parking unit also through ford and chevy sell only the complete unit
you can buy aftermarket parts but make note...there is no internal parking pawl in the transmissions equipped with driveshaft lock...so if it fails ...wave goodbye to your rv.
Hydraulic pressure releases brake...a fail safe type mode.
have your unit inspected by a pro...
