But, just to check Frank, both top and bottom have rubber bellow. One is part of the test tube or rubber tee-tee and the other stand alone with opposite the removable end plug. I have come across several trucks with the second little rubber bellows missing. That's where the crud creeps into the non rubber slide pin. I know what you mean about test tube slider though. You can take this out and put it back in without taking the caliper apart though, but it's easy to get it twisted i there. If it's not lubed then when you undo the sliding pin it twists the rubber. If this is not straightened out again then it leave a dirt channel. TBH I think that the whole thing is a pretty crap design. I have had Toyota almost since I learned to drive and have worked on them all. The brakes are something that have been consistently poor. Sitting where they do in all the muck, you'd have thought that they would have designed something better. Oh well. I just grease that little tube up well and it slips into the hole in the caliper. I have had many where the PO has filled that tube up with bloody copper slip (not grease in my view) which sets hard and binds the moving pin.
Chris