Mine just gave up recently, did the manual conversion on the stock hubs. Much more reliable now.
http://www.ford-trucks.com/article/i...cuum_Hubs.html

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99 xlt supercab xlt 4.0l ohv 4x4
mirror tint all around
2 piaa 580 lights and 2 220w dick cepek lights
100w pa system
2"front/1.5 rear lift
1 10" pioneer champion sub/ 1800w jl amp/ kenwood HU
31x10.5x15 Pegasus A/T