Found the solution. I am posting a new thread to inform anyone with this same problem of a possible cure. The transmission frequently did not shift from 3 rd to 4th on my 1996 Dodge diesel truck until after I backed off on the speed and then it would shift after so many seconds. The truck ran great other than that. The transmission had been taken apart 3 times and nothing was found, until my mechanic contacted the Chrysler Corp and via,via was told that the groove on the inner seal on the front clutch drum had been cut too deep during manufacturing. There is an oversized seal available which fixes the problem. It is manufactured by Transtec. I hope someone else with the same elusive and maddening problem can use this information and save themselves a high blood pressure crisis and beaucoup bucks. Thanks everyone for your input.
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