90 300zx NA a/t shifting issues

[300zxtillidie]

So the past couple months I've been in the process of resurrecting the NA with a/t after it was left in the unreliable possession of an idiot who couldn't tell his own a** from a hole in the ground. Basically have rebuilt the whole top end and replaced and/or cleaned up everything I can think of aside from a new engine bay wiring harness. So here's the problem, when I'm driving it just doesn't want to shift when it's supposed to unless I get on it and then seems to respond a lot better but not perfect. Ecu has codes 34 and 42. The knock sensor has been cut and dangling since day one, and the fuel temp sensor circuit I gotta do some testing of the wires back to the ecu. Don't think they are related to my current shifting issues, but you never know with these cars. And also have ran Diagnostics on the TCU and the only code I get is for the throttle sensor circuit. I've had several other Z owners/enthusiasts tell me to try checking the shift solenoids even though I'm not getting any codes or MIL lights. And also when attempting to switch from D to 2 or 1 there's no difference in engine behavior. But my Lil bro's grand prix just jumped timing so I gave him my camry that I had been using for a while. So my Z is now my daily, and with gas prices where they are I can't afford to be rolling around everywhere I go at 3-4000 rpm. Any suggestions or ideas on what to check and best way to do so without pulling the transmission would be greatly appreciated!!!

[300ZXttZMAN]

Moved to Z32 technical.

Have you checked for codes?

[DCaff300ZX]

I'm not an expert by any means in this area, but my AT NA was much the same in a gradual manner as yours from when I got it in 2003 until after I took it to a trans specialist for a fluid change in 2008 or 2009, and they mistakenly did a trans FLUSH which as many know is the death of a Nissan AT in most cases from the crap being flushed back into the trans guts from the filter screen.
The explanation I was given by my mechanic is he felt the trans was slowly failing from the beginning, and finished off by the flush job...and may be the course (minus a trans flush hopefully!) that you are on. The Nissan AT is not among the most reliable nor strong long-term units, especially if it hasn't been maintained well with fluid changes or abused.
Another possibility I've read of are speed sensor problems, just not sure how/where that fits into your issue.