Trying to find out if the hard to turn steering wheel is due to the large size tire (37 to 35), or it’s because of the power steering pump. Anyone experienced similar issue?
2006 4.6

 

Bigger tires are harder to turn, but that's something nobody is going to be able to diagnose over the internet. I had 35s before and didn't think it was hard to turn.
Another thing to look at might be your intermediate shaft if it's super crusty I think it can contribute.

 

Might be a combination of a weak pump and the bigger tires
* Replace the pump and hope for the best
If you have ***** like Mighty Mouse, you can pump the tires up to 60 lbs. and road test it
If it steers like a dream at 60 psi, there's no need to replace the pump
I put a whole bunch of pumps on at the dealer HOPING for a good result only to find that the tires were the problem all along
People would buy a new Bronco, lift it and put big tires on it, then come right back complaining of lack of assist
I learned to just tell them my heart pumps **** for them, wish I could help
That said replace your pump and become a believer too