The last 2 months my 89 2.6 has developed an intermittent "groan" sound when shifting from 2nd to 3rd. Right after the normal "clunk" of the shift itself, there's a soft but audible groaning noise. Doesn't happen all the time. Doesn't happen with very soft or very hard shifts. Doesn't happen as far as I can tell in any other gears. Can't tell if it's temp dependent or not. Trans fluid checked and topped off. Car has 63K miles and has not had 60K service yet. Any ideas appreciated. Thanks