I drive 1994 gmc sierra 5.7 SLT it idles fine in park and in gear at a stop light. Now when I take off from a light it seems to have little to what power and it takes forever to get up to speed.
Now when I take off and get up on it it shifts
from 1st to 2nd at 3500 rpm is my
transmission going out?
Could be a torque converter, or the pressure seals are getting brittle inside the tranny and leaking necessary pressure to make it shift when it should. You can try servicing the transmission and add a can of TransX then fill to specs then drive it as you normally would, the TransX will soften the seals and might cure your problem for a while, but the seal damage has already been done so it is hard to say how long it will work for you. This is assuming that the problem is actually the trans and not an engine or emissions problem.