It hasn't engine braking, when you release gas it disengages... so if no KD cable it will shift.. early but shift? So probably the lack of KD cable will not be the shifting problem?
No engine braking in first usually means something is hanging up instead of completing the shift.
Without a TP setup connected it would still shift, but way early and soft.
If you can't force the shift, then likely you will need to pull the valve body again and clean it real good paying special attention to the valves and valve bores.
It is a really good idea to move the valves with a small pocket screwdriver or pick to make sure they can move.
Over torquing the valve body can stick valves also.
You may even have to pull the tail shaft housing and clean the governor.
