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Paul Bennett · 07-19-2019, 06:57 AM

Above 27mph, voltage is applied to the primary overdrive coil which sucks in the solenoid shaft engaging overdrive. Immediately after the activated solenoid's shaft reaches its end-of-motion, the primary coil within the solenoid is disengaged and voltage is then applied (again this is within the solenoid) to a secondary holding coil which as it's name implied, continues to hold the overdrive shaft in the 'active' position. Reason for this setup is that a great force is needed to jam the shaft into overdrive position but once there only a small force is needed to keep it there, hence the low current secondary coil.

In the case where the solenoid continues to draw a large current after activation, the contacts which change voltage from primary to secondary coil are just not working. The solenoid needs attention. One possibility is a leaking seal whereby transmission oil has leaking into the electrical area within the solenoid, and the contacts have gone bad.

No reason to mess with the relay or other electricals outside the solenoid as the problem lies within. See Vintage Auto Garage .com for a fix.

07-19-2019, 06:57 AM	#8
Paul Bennett Senior Member Join Date: Sep 2016 Posts: 628	Re: Overdrive experts I need some help. Above 27mph, voltage is applied to the primary overdrive coil which sucks in the solenoid shaft engaging overdrive. Immediately after the activated solenoid's shaft reaches its end-of-motion, the primary coil within the solenoid is disengaged and voltage is then applied (again this is within the solenoid) to a secondary holding coil which as it's name implied, continues to hold the overdrive shaft in the 'active' position. Reason for this setup is that a great force is needed to jam the shaft into overdrive position but once there only a small force is needed to keep it there, hence the low current secondary coil. In the case where the solenoid continues to draw a large current after activation, the contacts which change voltage from primary to secondary coil are just not working. The solenoid needs attention. One possibility is a leaking seal whereby transmission oil has leaking into the electrical area within the solenoid, and the contacts have gone bad. No reason to mess with the relay or other electricals outside the solenoid as the problem lies within. See Vintage Auto Garage .com for a fix.