I have a 1987 740 Turbo with 5 speed that I recently changed the o-rings on the solenoid. Today, the overdrive would not engage once the car had been driven for 10-15 miles. I had to turn the overdrive on and off several times during the drive and it became increasingly difficult to engage until it just refused to engage no matter how much I tried. The light on the dash goes on and off with the switch but the overdrive itself would not engage. I have changed the fluid to Type F in the last month.

I have reviewed the posts and it seems that I may need to change the actuating piston seals. Is there anything else that can cause these symptoms?

Thanks for any help.

Gary