My son in law'* 95 Suburban started not shifting up without lifting off gas. He said it was like that for about a week and now it will only pull in reverse and first. It is just like you shift to neutral on upshift. I unhooked the battery for reset, no help. No codes on scanner (OBD 1), TPS tests good, A & B shift solenoids check good, 1-2 accumulator looks good. I don't have a pressure gauge, but it pulls strong in reverse and first, no slipping. I have the 2-4 servo out. The Teflon seals look perfect but the red o-ring has an odd looking place on it and the servo piston bore is discolored at the bottom and shiney clean the rest of the way around.Am I looking at my problem here?

I know this is going to sound weird but I would check the ignition switch. I've seen where the switch wears out and won't provide enough amperage to operate the solenoids in the transmission.

Thanks, but don't, seem to be anything there. I have also looked at the plugs and they appear clean. Also looked at the wiring harness for any damage and haven't found anything. Still pulling out my hair.

Just for giggles I would wire up something like a fog light and see if the power feed to the transmission will light it up. There was also a post on here not to long ago about a guy who replaced the transmission and it still had a problem and it turned out that the driver in the PCM was bad so I would check out the integrity of control circuits from the PCM as well.