450E Winding sound when in reverse

[greg noble]

i know my 450e has reverse issues because reverse dies when it gets warm,but its fine for about 30 minutes except for the winding sound that i hear in reverse,does this sound point to a particular problem with the HLR?
The manual says you can increase the HLR pump pressure by addin or subtracting shims,how do you do that and where do you get the shims?thanks