Screwed Up OD. Any Guesses?

[mp88]

Hi Everyone. I've been looking around for an opinion on this problem and figured this might be the place to ask.
So here's the deal:
I have a '94 XLT, 4.0l V6, 4wd, 129k miles, had a tranny flush about 2 months ago.
My truck goes through the gears as normal. Once it hits "4th" gear I'm hitting RPM's around 500 higher than I normally do. Yes, I'm positive that it is not in 3rd gear. As weird as it sounds, it is going from 3rd gear to "3.5th gear".
The check engine light came on and it read an OBD-I code of 335: EGR sensor voltage out of range. There were no vacuum leaks in the EGR, but my coolant sensor was broke, so I replaced that.
One of the oddest parts of this, is that it doesn't happen every time I drive. Only every once and a while. It also seems to happen when I park the car facing uphill (if that makes any sense).
If any of you guy/gals have any input on this I'd really appreciate it.
Thanks.

 

[MrShorty]

It sounds like you are either missing 4th gear or TCC lockup. Both are electronically controlled by the computer. The first thing I would suggest would be to figure out which you don't have.