I do have harsh shifts at highway speed’s I’m not sure if it’s at the downshift or the upshift but it usually happens around the 50 and 60 mph area I believe it’s on downshift if I let my foot off the gas pedal quickly instead of smoothly the shift down you can feel as a jolt in the car

 

I am not sure where that connecter is either however mine only happens on cold starts whereas his was happening always

 

Are you sure the jolt you feel when you suddenly let off the pedal isn't the slop in the drive train that these all have? All of these vehicles have slop between the front drive shaft, T-Case, and rear drive shaft. That slop can be a clunk with sudden on or off throttle conditions at any speed.

I have learned to not suddenly get on or off the throttle to avoid the clunk. I'm sure others here have noticed this as well.

 

@Oshawa_D2 The harsh shift will be all shifts very similar to low transmission fluid or pretty thrashed one.

I checked my notes I have had that code twice, both times it was related to loose grounds, the one from the block to firewall drivers side and the other was cleared up by checking every ground. My bet is you have a bad electrical connection somewhere.

 

“P0748 - Pressure regulator check (S/C to +12V).” That’s the code

what does it mean check s/c to +12v

it something easy that I can inspect? And what would I be looking for? Or the fact that this issue only is on cold starts is an indicator of something electrical at start up? Kind of at a loss with this

 

@Oshawa_D2 The sensor is inside the transmission, so not trivial. But my bet is a bad electrical connection.