My 18 year old son's recently purchased '88 245 with manual transmission & overdrive has proved sluggish to shift on the colder mornings these days in the upper midwest. I'll be out of the country till Jan., so I'm trying to advise him from afar. All my other bricks are auto. The car has about 140K and the tranny oil was changed at least once by the PO, probably at Jiffylube, so it may be running 80-90 wt. dino gearlube. I'm thinking it would be much happier with synthetic. Should it be flushed with ATF first, or just drained and filled? Any precautions? I've already warned him not to drain before freeing the upper bolt plug with a 6 point. Are these bolts square or hex? I assume Redline MTL is the fluid of choice, but would be grateful for other suggestions. Thanks!!