Hello! I have a 1955 Chevy 6500- Series 2- tonner that did the same thing. the previous owner disconnected the vacuum lines, and ran a wire through the diaphram to control the hi/lo. if the gears didn't mesh correctly, the rear-end would freewheel since it was in neutral. I hope this information helps. You may also have a leak in your diaphram, assuming that you have a vacuum 2- speed. I fixed mine, using a semi-truck tire "boot" to replace the old diaphram material. You can check for a vacuum leak with the engine idling. If you hear air escaping from your lines or the pumpkin, you found your problem. if you don't hear any air, your plunger might need to be lubricated. Just un-bolt the 2, 9/16" bolts holding the unit to the axle, and it should pull right out(if you have enough slack in your hoses) I hope this helps. Good luck and Happy Bolting! Bill Hickey New guy 1955Chev 2nd series 6500 Series E-mail
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