[one3n3my]

I had the same issue with my 70. Check the prop valve and the lines as it could be losing pressure there. Also check the booster, I replaced it twice before it was functional.

I had come to find out the previous owner had replaced the line with a larger diameter which was causing the rear breaks to not receive the pressure that it needed to engage.

I replaced the booster, master, brakes, and lines in order to figure it out.