I have been towing a 7800 lb enclosed trailer for several years w/Escalade ESV. Lately OD would occasionally slip, came home Sunday pm w/o any problem and dropped off trailer. Went to use it today (w/o trailer) and no OD. Ran a scan log and it would not shift into 4, and no VSS speed. The speedometer works correctly and 1, 2 & 3 work fine. Is it just the VSS, fluid, 3/4 clutch pack or ?

 

Check connector on VSS first (passenger side of tailhousing). Or... Maybe the little screw/bolt that holds the sensor in place isn't securing the VSS. W/O the VSS, the trans' shifts won't be as accurate as normal parameters would.

 

Finally got around to changing the sensor. That did the trick...thanks for your help.