If this is a maunal transmission with a Lycock Overdrive, three areas to inspect AFTER making sure the transmission is full of transmission fluid. Well, while you are under there, check number two as well.

1. If your dash light goes out when the OD does not work, replace the 4th gear switch on the transmission.

2. Clean and tighten the contacts on the solenoid on the overdrive unit.

3. Two actuating piston O-rings need replacement. The overdrive has to come off the transmission. The tranny can stay in the auto. See the 700-900 FAQ's under the Features section at the top of Brickboard pages.

If your actuating piston O-rings are factory original, you may also need to change the actuating pistons as well.

The actuating piston O-rings in some of the late production 87's had Teflon O-rings. It takes about 660C (350F) to soften the Teflon O-rings sufficiently to stretch them without damage to install them. Without the heating, the repairs done by shops not using the heated O-rings failed well before the "normal" expected lifespan of the O-rings.

To solve this, the actuating pistons were replaced with an older style which allowed the use of rubber O-rings not subject to the heat requirements needed for installation.

Duane