I have a 1987 El Camino with a 2004r. The other day it began to not shift into 3rd gear. I would press the gas and let go and still it would not upshift. Today going up a hill at 35mph it finally upshifted into 3rd gear. After which I stopped at a stop light and then proceeded in which it shifted into 3rd and then into overdrive. What could be casing this problem? Vacuum leak, solenoid, or computer problem? The TV cable has tension when I pull it.

could be a sticking valve in the valve body, if you haven't done it lately a fluid and filter change may help ...............Dan

Ok, now that I was able to get on some higher mph highway the transmission does shift into all gears, but it takes a much higher rpm to do so. 1st to 2nd is ok. 2nd to 3rd shifts between 2000 and 2400 RPM. 3rd to overdrive shifts at around 2700 to 3000 RPM. In overdrive I can feel that things just don't feel smooth like it's supposed to be.

Now it sounds like your TV valve is sticking or the TV cable is adjusted too tight making the tranny think your foot is further in it than it really is............Dan

I have read, but do not know for certain, that an improperly adjusted TV cable on an OD tranny must be adjusted correctly. The article stated that failure to have it adjusted properly will cause damage to the transmission. It what I read is true, it would be a wise investment to get a pro to adjust the TV cable.