If memory serves, the gaskets where .015". If it was much thicker than that, you could have changed the distance between the pump piston outputs and the transfer block enough to allow the fluid to escape back into the pump housing.
I've never had my poppets out, so I have no idea how many shims are in it. Did you follow the assembly note that says "Be sure open ends of guide point outward."
Not sure you should be able to feel the individual hydro motor pistons when you spin the wheel, but as long as there is more friction when you are in drive, the transmission should be working.
Here is what one of my manuals suggests for trouble shooting the T66X:
PROBLEM/FAILURE PROBABLE CAUSE
1. No output torque forward and reverse 1A. Low on oil
1B. Tow valve in up position
1C. Input shaft key sheared/ missing
1D. Linkage off or broken
1E. Soft ride valve stuck
1F. Internal wear/damage
2. Momentary lack of output then power surge 2A. Soft ride valve stuck
3. Initial output OK but loses torque after running 3A. High pressure relief valve spring getting weak
3B. Refer to 1 A
3C. Oil temperature high due to overload or ineffectual cooling
3D. Water in oil
3E. Internal wear/damage
4. Output power less than original 4A. Linkage out of adjustment
4B. Refer to 1 F
4C. Loss of engine power
Edited by New.Canadian.DB.Owner, March 03, 2013 - 04:26 PM.