How did you disable the rear brakes?
I shouldn't say disabled but I used the prop valve in the car and made the rear brakes basically not function.
I had the car on jack stands I thought what if I start the car put it in gear let it run apply the brakes see if I hear a noise. If used the brakes too hard it would stall the car so I would apply a little gas to load everything up to see if I would hear any noise. I didn't hear anything so I went to the prop valve turned it all the way out to decease the rear as much as possible. Then started the car and put it in gear pushed on the brakes. No matter how hard I pushed on the brakes I couldn't get the car to stall. I could see there would be some load meaning the were still kind of working but not enough to stall the engine with it just idling. I figured that was the closest I would come to taking the rear brakes out of the equation.