I have an 05 sierra 1500 sle w/ a 5.3 157000 miles on her. I bought the truck a year and a half ago with 125000 miles on it. Only issue in that time was front axle hubs needing replaced. I noticed yesterday significant slippage in shifting from first gear to second while moving. when its about time for the engine to shift it acts like im in neutral and revs high with no power supplied to the wheels and after a couple seconds shifts. if i stay on the throttle it will take longer for it to shift up, and if i lay off it will shift quicker. im concerned the transmission may be goin out, i have not touched it since i bought the truck out of concern of fixing something that wasnt broke. the only thing i can think of that may have caused this is loading 2200 pounds of concrete in the bed (i know, i was a little worried but figured it could handle a ton right?) but only drove a couple miles loaded. if anyone could let me know what they are thinkin is goin on i would appreciate it, id like to stay on top of this issue if its something that needs to be addressed.

 

Sounds like you have a sticky valve or two in the tranny. If the tranny fluid has not been changed I suggest you pull the pan and change the fluid and filter. When putting the fluid in add a bottle of Lucas Transmission Fix. If you don't see an improvement you will need to take it to a shop for repairs.

 

should i keep the fluid i just drained from there and put it back in after i replace the filter or should i put new fluid in there?

 

Put new fluid in.

 

thanks for your advice, ill see how it goes this weekend

 

Exactly what I did with my 97..Fixed it right up.....I was getting a p1870 code (trans component slippage)....Are you getting any codes?

 

havent hooked it up to any diagnostics, just have a buddy that is a fleet mechanic for a large company with military training and he said the issue is either bad fluid or shift solenoid. or just an old transmission ya know