sure-grip issues

Just installed a 742 with sure grip and 3.23 gears. Let it run for 10 minutes at approximately 40 mph per the factory manual (that is what is listed if there is noise and to change the fluid and test before disassembly...I thought it would be a good idea to get everything lubed without stress). Put it on the ground and it slips and gets a moan. Is this just the clutches or more? Looks like the clutch swap out would be a semi easy ordeal.

Thanks

67 Dart/360/727