On the drive motors there is a small hydraulic line on each one that goes to an aluminum block along with a bigger hydraulic line from the right front side of the tandem drive pump and there is also a yellow wire that comes out of this block. What is the purpose of this block and is there a relief valve in it also is there a main relief or bypass valve that would be for both forward and reverse
Sounds like case drains to me, the large hoses are F&R hoses and the case drains take internal leak off oil to sump so motor seals are not subjected to high system pressures.
If your motors have three hoses each, the smaller one is a case drain, if they have four hoses each, the smallest ones that are connected to a solenoid valve, which may be what you're describing as an aluminum block, would be parking brake lines. There are four high pressure reliefs, one for each main pressure line to the motors, they are in the drive pumps above the main pressure ports. Relief issues will usually but not always be limited to one side in one direction.