2007 GMC Sierra 1500 4wd Shift Issue

[Boomer Coleman]

I have a 2007 GMC Sierra 1500 5.3 4wd NBS that is having shift issues. It is shifting hard into 2nd gear from first and when it starts doing this the trans starts to slip. The speedometer also will bounce along. Today it ran great for 30+ miles, I stopped to get fuel and when I went to crank it back up, it struggled and now the Tach doesn't work.

 

It does not shift hard all the time. There is no constant variable that is present when it starts to shift hard. Will the speed sensor on the transmission start this? I have drums in the rear and do not see a sensor anywhere back there. I am changing both front hubs this week do to deer season is coming up and one is starting to make noise but my problems were present when the hub was good.

 

Thanks

boomer