95 GMC Jimmy tranny problems

[kenthomas4]

ok i have a 95 jimmy 4.3l 4x4 with the 4L60E, i knew it had a small leak and was getting ready to fix it. Two days before i was going to fix leak it started slipping getting on the interstate so i drove the 2-3 miles to my parents and checked the fluid it was down a little so i added fluid and got it to the hot mark. When i left my parents it drove fine with very little slipping for around 4-5 miles at which point it really got bad the rpms would shoot up and then it would catch and go but i could only run about 35 mph. When i would stop it then go again it would shift out through 3rd. Saturday i changed the filter, fluid, and pan seal (which was leaking). Took it for a test drive up the road and really had no problems. I let it sit over night and on sunday drove it and once again same problem with it slipping and not going into over drive.If i start out with it in overdrive it will only shift through 2nd gear but if i start in drive it will shift through 3rd. Not quite sure where to start because check engine light has not come on at all. Any suggestions please
Thanks in advance

[maxwedge]

Internal problem almost definitiley, a trans scan at a trans shop will tell you if the solenoids are operating properly, after that it is coming out.