secondscene

I just recently (570 mi ago) finished a rebuild on my 22re motor. Runs great!
I am having a weird no crank issue that manifests only when the motor has been sitting for 5-8 hours and has happened so far only in the cold.
The truck has a m/t and I don't have a starter relay.

The battery is new, just replaced last week and the starter was replaced about two months before the motor went.

Now for the odd part. When the truck will not crank, I get the click from the passenger side and a slight whine. Nothing out of the ordinary. However if I put the truck in gear and turn the crank bolt to rock the truck a little then the truck turns right over. I have not been able to figure out why it works, only that it does. This method doesn't work unless the transmission is in gear.

The truck doesn't have a starter relay but I will be installing one just to check if low voltage to the solenoid is an issue. (I am an idiot and found the starter relay, works just fine)
The cables to the starter and block, both positive and negative, have been replaced and the ground connections are clean.

Any help/ideas would be appreciated!