I have a 460 that piston 5 is at 30 psi. My tranny shifts very hard. I have replaced all the sensors, neutral safety switch, and did a full service before I found out the motor had issues. It still ahifts very hard. Could the motor be causing this?

 

Absolutely. A badly performing engine will affect shifting of your transmission since it is electronically controlled by the PCM. You basically have a seven cylinder engine. The cylinder compression readings between the highest and lowest should be within 20 percent of each other. I like 10-15 percent. It's worth warming up the engine and squirting a small amount of oil into the cylinder. If the reading goes up, you have ring issues. If it doesn't, look for a valve problem which is what I suspect.

 

If you did not find anything with the check last posted, you can look into what is called a leak down test.
The tool is threaded into the spark plug hole for that particular cyl after it's piston is brought up to the top of it's travel.on it's compression stroke.
Then a few pounds of air is inserted in the cyl and if you hear air leaking into the intake, it is an intake valve problem. If you hear air leaking into the exhaust, it's an exhaust valve problem. If you hear air leaking into the oil fill hole , you confirmed a piston ring problem.
Some places will rent these tools , might be a good idea to check.