brought truck back in for a 3rd replacement ofmy power mirrors. One mechanic mentioned the " slip yoke" in the trucks are causing problems ? All Chinese to me
This is exactly what it feels like on my truck. If I come to a stop, regardless of a quick/hard stop, or soft and slow one - I get a 'thump' as soon as I let off the brakes. This would happen on drive shafts with slip yokes (think a splined attachment on the drive shaft, that slides in and out of the transmission, done intentionally to account for the natural movement of the axles and suspension while driving) as they aged or the grease on the splines themselves dried up. It just doesn't make sense on a brand new truck with <10,000 miles.
What happens once the splines are dry, is you'd get some binding as the slip yoke tries to go back to its neutral position. When the drive shaft is able to overcome the resistance/binding, it slams into place, either at the tail end of your transmission, or at the split between the drive shaft itself (these drive shafts are at least 2-piece units, maybe even 3 if there's a set of slip yokes under the rubber boot on the rear part of the shaft).
In my case, if I put the truck in neutral before coming to a stop, it doesn't do it, until I put it back in drive - which has led me to believe it's a cascading effect of the way the transmission and torque converter behave, and uber-long drive shaft set up on a 244" long vehicle.