Tranmission 4th gear issue w/ P0743 an P0748 Error codes

Okay guys Last time I got some real good avice and I'm almost ready for a road trip. I got one final issue. Recenly my tramission and torque converter was replaced on my 98 Windstar 3.8lt, and a AXODE 25SP 4 speed auto tranmission. O have one final issue that I'm not to sure about. I got these 2 codes P0743 and P0708 that I'm trying to figure out. The tranmission shifts just fine from 1 to 3 but at the 4 gear it does some weird rpm thing. When I approach about 40 and 45 mph thats when normally the 4 gear kicks in. On mine the RPMs seem to go up about 500RPM's then kicks back down to between 1500 and 2000 rpm's depending on driving conditions. Then once in a while the 4 gear feels like it cant stay engaged and I can see my rpms changing. I've replaced my TRS and adjusted the linkage seemed to help but stil 4th gear issue was not resolved. Any ideas or suggestions will help.
Thanks

FIRST thing that I would do is take it to the shop that did the tranny job....as it should still be covered....and, if so, repair should be free.

P0743 Torque Converter Clutch electrical system malfunction

P0748 Does not come up in my alldata....but a yahoo search brought up
P0748 Pressure Control Solonoid Circuit Electrical

This link describes the code and how that circuit works.... Take note that this is a GM 3.8L. But the code means the same thing....also same description on dodge dakota, mercedes, saab....and so on....but I chose this one as it tells you what it is doing.
http://www.ls2.com/boggs/a4/DTC%20P0748%203.8.htm

I think you got the wrong code.I have the following:
P0743 - Torque Converter clutch circuit
P0708 - TRS circuit high input
Now I have replaced the TRS but not to sure about the 743. If you have any info let me know. Please