resilient o ring 150 lower power mandrel 148 has an external threaded surface 152 near its upper end which is threadedly connected to an internal threaded surface 154 located near a lower end of an upper power mandrel 156 of mandrel means 124 upper power mandrel 156 is spaced radially inward from relief chamber case 47 of housing means 12 to define an annular relief chamber 157 an annular floating shoe 159 is disposed in relief chamber 157 and has annular inner and outer seals 161 and 163 which provide a sliding seal against cylindrical outer surface 165 of upper power mandrel 156 and cylindrical inner surface 167 of relief chamber case 47 respectively the lower end of annular shoe 159 is communicated with well annulus fluid through relief port 45 floating shoe 159 floats within relief chamber 157 to prevent hydraulic lock up of mandrel means 124 relative to housing means 12 during telescoping movement therebetween a power mandrel retaining cap 158 is threadedly connected at 160 to an upper end of upper lower power mandrel 156 an outer cylindrical surface 162 of upper power mandrel 156 is closely received within an inner cylindrical surface 164 of an actuating mandrel retaining cap 166 actuating mandrel retaining cap 166 is threadedly connected at threaded connection 168 to a lower end of an actuating mandrel 170 of mandrel means 124 an outer cylindrical surface 172 of power mandrel retaining cap 158 is closely and slidably received within an inner cylindrical surface 174 of actuating mandrel 170 thus relative sliding movement is allowed between upper power mandrel 156 and actuating mandrel 170.