It is also possible that your xmsn is slipping once the viscosity of the oil is decreased at operating temperature, check your powertrain filters for contamination (metal or friction disc material), you should also check the xmsn suction screen (this is where the majority of coarse material is caught before heading to the powertrain pump). Here is the procedure:
Remove Transmission Magnetic Screen (Power Shift)
start by:
a) remove floor plates
1. Remove the oil from the transmission and the bevel gear case.
2. Disconnect oil tube (2) from housing (1).
3. Remove four nuts (3) and washers that hold the housing to bracket (4). Remove the magnetic screen and the housing.
Install Transmission Magnetic Screen (Power Shift)
1. Put the magnetic screen (2) and housing (1) in position on the bracket. Install the four nuts and washers that hold the housing in position.
2. Connect oil tube (3) to the housing.
3. Fill the transmission and bevel gear case with oil to the correct level. See LUBRICATION AND MAINTENANCE GUIDE.
end by:
a) install floor plates
Disassemble Transmission Magnetic Screen (Power Shift)
start by:
a) remove transmission magnetic screen
1. Remove tube assembly (5) and magnets.
2. Remove element (4) and the spring washer from housing (2).
3. Remove cover (1) and seal (3) from the housing.
Assemble Transmission Magnetic Screen (Power Shift)
1. Install a new seal (5) in the housing.
2. Install cover (2) and four nuts (1).
3. Install the ring, element (3), tube assembly (4) and magnets.
end by:
a) install transmission magnetic screen
Black, fibrous material will be friction disc failure, steel could be the reaction plates, teflon would indicate a failed piston seal. Regardless, any large amount of contaminants in the suction screen generally means it's time for a major overhaul.
As a side note, if you know how old the powertrain oil is and want to reuse it in case you find there is no suction screen contamination then carefully drain the oil into clean pails for reuse (not recommended procedure but if you are clean and careful and the oil has low hours then you can save yourself a few bucks).
Good luck!