Cat 931 steering problems

Hi all I got a cat 931 28Y and having some steering brake issues. The left brake doesn't seem to work very good. Have to press the peddle very hard to get any brake. Right side brake is a bit easier then left. As the machine gets warmer the left brake gets worse. I notice there is a pulsating growling sound when pressing on the left brake when the machine is moving.

I checked the adjustment of the left brake, but I've seen two different ways to adjust it. Top adjuster bolt you tighten up, then bottom bolt tighten then back off 1 1/2 turns, and then back off the top bolt 3 1/2 turns. Or another one that said back both adjusters 1 1/2 turns. I did the first one, 3 1/2 turns on the top bolt.

Steering valves I think are working. They are pressing on the cams and if you are moving, push both peddles in 1/2 way and machine stops, if you raise either peddle it will start moving again. Where does it get the pressure/oil from? The transmission or hydraulic reservoir?

The bevel gear oil is low, i need to add some 30w and also when checking the final drive oil levels there was pressure in the left housing when removing the plug. Oil levels were bolt good. Is there a vent for the final drives?

Thanks all