I recently rebuilt my 91 GMC 700R4, first time. Everything seemed to go pretty good. Took it for a test drive (about 5 miles)and seemed to shift perfect, all gears. After setting over night it was shifting late and kinda hard in all gears. I disconnected the TV cable with the engine off and pulled it in and out kind of quick about 20 times, reconnected it and it shift great.
Has about 150 miles on it and it shifts like it should or appears to, except into overdrive. It doesn't want to shift to OD till 55-60. It has done this for a while and is pretty consistent.
At about 45 if I ease off the accelerator just a little it will shift and feels like a good shift.
Lockup is working. Down shift seems to work like it should. RPMs are all good.
When first put in the truck the PSI was all in the range from the ATSG manual.
I have adjusted the TV cable in both directions and doesn't appear to make a difference on 3-4. It will start making other shifts worse. I have started over with the adjustment a few times and it's about the same.
Is there something else I should be looking at, other then the TV?
I did a stock rebuild other then alto 8disk 3-4 pack. No shift kit or servos.
Any help, advise or criticism would be greatly appreciated.

I verified full pull at WOT many times, but not convinced that that's not the problem.
I ordered a transgo shift kit jr, after seeing it suggested on this forum many times. should drop the pan and VB before the weekend. Anything I should look at while its apart. Or anything else I should do while apart.
Am I'm I heading in the right directions?
Any input would be greatly appreciated.
Also, any input on what I may be doing wrong on my post, as to not getting responses, would be greatly appreciated.
Mike