hi all, bought my first zed!!..its an imported n/a fairlady, beautiful car, solid, lovely engine, but i have a strange problem with o/d.....my box changes up and down fine, kicks down, holds the gears, no untoward noises..or smells!!!...but when i engage overdrive, it does engage, but if i lift off, even momentarily..it drops a gear.....it will hold overdrive with cruise on no problem at all...this is a frustrating problem on twistier roads!!...any advice greatl appreciated as its spoiling a lovely car..