Hey, I have a 94 Yukon 6.5l 4L80E with 225000 miles on her. Here is the issue. Normal driving flat ground shifts fine. If i give it some diesel from a stop or if i am climimg a hill from a stop, the shift from 1 to 2 seems to come late and the engine defules then has power again then defules then has power again in rapid succession. Until it finally shifts into 2nd. Then its fine again. I have stood on the brake and stepped on the accelorator to see if 1st would slip and i dont believe it did. So i replaced the shift solenoids to see if that would help but no. still the same. Now i am thinking it is the speed sensors but before i replace them I would like a little input/suggestions from the gurus please. Thanks

Take it to a technician who has a techII scanner. Explain your problem.
I can guess it could be your Throttle position sensor. They cost a bit much to replace. Snap diagnosis is not the key here and replacing a part without verifying the problem can cost mucho dinero.

Hey, I need to update the issue. I drove it arround pretty hard last night to see if i either get it to break or set a code. the problem is not only in 1/2 but i believe all gears if i really get on it and if im in say second and give it more diesel but not enough to down shift. It acts like the engine defules for a second or 3 then takes off again in the middle range of that gear. I have a teck I tool and hooked it up. No codes trans or engine and everything I saw in there seemed correct. Anything speciffic I should look at? I guess next ill hook up a pressure guage and see if the pressure solinoid amps matches the guage by the table in the book. I believe the problem is in the tranny or something to do with the load the computer thinks the tranny is under. I will take it to a trany shop if i have to but i really like fixing these things myself. I it comes down to a rebuild of the tranny i believe i can do it but as you say these things are not cheep. Thanks