I can be driving down the road minding my own business when all of a sudden, the transmission will come out of overdrive (o/d) and the little yellow arrow will pop on.
I'll play with the o/d button on the sifter to no avail. When I come to a stop, and play with the o/d button a few times, the arrow light will turn off and I am back in overdrive. Anything serious?

I had a similar problem that was fixed for maybe $35 a few years ago.

Your OD relay is either going bad (P/N 3523804, $30-40) or it's simply loose in the fusebox socket. My 88 does this occasionally. It's the tall relay all the way up front on the right. A couple wiggles to re-seat it in the sockets and all is well. If yours is original, it might be time to replace it anyway. Keep the old one as a spare. Sometimes just plugging/unplugging it will clean up a dirty contact enough to work.
Remove ashtray, lighter, 2 screws, coin tray, pull relay straight up.
Don't pay anyone to install it, its easy and all you need is a phillips screwdriver.
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Rob Bareiss, New London, CT 86 244, 87 244, 88 744

Thank you.....you're an all right cigar! I'll give it a try!

http://www.brickboard.com/FAQ/700-900/TransmissionAuto.htm#AW7071OverdriveRelaySwitch
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Thank you for the tip. I'm on a mission!