98 Tahoe revs high and slams 1st-2nd and wont go into overdrive!

I have a 98 tahoe with about 120k on it, this is the first time i have seen this problem. I have had it shift hard from 1st-2nd before, but now it is winding up to 3-4k and then shifting. I can get it to shift if i lay off the gas @ 2500 and get back on it, but I am also having a problem when I get on the highway, it seems like it will not shift into over drive. the rpm's get to about 3000-3500 and if i let off the gas i slow down quite a bit and get back on it and it just jumps right back to 3000.

Any ideas? trans fluid looked ok, but I have never changed it, and I have had it since 60k...I dont know if that would be the problem or not???

Unlike the older models with vacuum modulators, everything is controlled by the computer which monitors input from the throttle sensor, load, road speed etc. You may have codes stored. It really needs to be looked at by a transmission mechanic or other service provider.

if the transmission has never been serviced i would start there, not changing the fluid and filter properly is the biggest killer on transmissions, flush the transmission system and put a new filter on

Well, you have 60K (I'm assuming miles) with out changing the fluid, should have been done twice by now, start with that and the filter.

Second, a little know problem is loss of a good electrical ground for the transmission computer. The physical connection of an aluminum transmission mounted to a cast iron engine block with steel bolts can experience electrolysis which in turn reduces or eliminates the electrical ground between the trans. computer and the battery, thereby putting the transmission into "limp home" mode. After changing the fluid and filter, try creating a good electrical ground between the transmission and the chassis by running a wire from clean. shiny metal on the transmission to clean, shiny metal on the frame or engine.