Ordered parts online to rebuild calipers etc. The new rubbers for the slide pins came with another rubber 'bushing' I guess. When I took the old slide pins off/apart, there were no bushings on any of the slide pins. Looking in the service manual, no 'bushings' are shown anywhere. 2 Questions: Are the bushings even required? If yes, are they for the lower pin or the upper pin?

Where did you order the rebuilt calipers? My neighbor recently acquired this 2008 Frontier with new calipers and Black 314 method wheels. I'll ask if he knows where those calipers came from.

Didn't order rebuilt calipers. I bought a caliper rebuild kit and new slide pins with boots from Rock Auto. Rock Auto also has new and remanufactured calipers as well.
Just was asking what the "extra" rubber 'bushing' was that came with the slide pins. Service manual does not show or talk this extra rubber piece. Just was asking which pin it is for, top or bottom, or if it is even needed? (Will start rebuilding brakes this weekend (Nov 11) and was just trying to be prepared. Not sure if existing calipers/slide pins have the bushing or not. I purchased the truck used)!

The front brakes on the D40's have two different sliders, the lower pin has a land area with a rubber bushing that fits into it. Nissan often does that when sliders go into a through hole instead of a blind one, the rubber bushing acts as a seal. It can also serve to prevent the caliper from rattling.

Thank you for the response. Will respond again once I have completed the task. Like I said, I purchased the truck used so am not sure what has been done. It currently has 134,000 miles so I am sure brake work of some kind has been done.