1996 Dodge Ram Transmission does not upshift correctly unde

Can you describe what is happening? The heading for your post is cut off.

My Dodge truck has 138000 miles on it. The tranny has been serviced at recommended intervals. In the last 10000 miles the shifting of the transmission has become erratic. When pulling a load it pulls great in what appears to be first gear up to about 45 miles per hour and over 4000 RPMs when it does shift it seems to try going into second but does not then trys to bounce from first to third. If I let off of the gas pedal and slowly depress it, the transmission will stay in 3rd and then shift into 4th. All of this is occuring with the overdrive switched to off. I have rebuilt 6 or so automatic transmissions in the 80's but I am not familiar with the newer models. I purchased a repair manual for this model of Dodge truck and it gave the basics on the transmission and that is all. From what I have read so far, it seems that it may be the shift solenoid or the linkage adjustments. Any help you can give me would be greatly appreciated.
Miike

It sounds like it could be either of them. There is also a trans control module (TCM) that is responsible for shifting intervals. Has the check engine light ever come on or has the Over Drive light flashed, come on...?