4th gear disengagement issue

Hi there,

Just inherited an '89 740 Turbo automatic and I'm having trouble getting the
fourth gear in place when I depress the 4th gear button located at the side
of the shift selector. I'd would usually depress it many times before the
shift indicator light on the dash goes off and the tranny shifts into 4th
gear. There's about a 1000 - 1200rpm difference at speeds of 100/kph so in
terms of mileage I'd really like to get this solved. I do hear a faint
clicking I've noticed everytime I depress the button but in doesn't always
work.

Does anyone have a suggestion as to where I should start or diagnose?

Thanx,

Norbert

 

Clicking would be caused by a relay being activated, the shift not working
would be the overdrive solenoid, it probably needs replaceing. I have seen
this problem posted many times before, its either the solenoid, the relay,
or the wiring is damaged. Failing that, it's the switch contacts.
Since the relay clicks, it probably is working fine, but if you do the
solenoid, you may as well get a new relay.