btw, transmission oil temps usually are not as high as engine oil temps. In
this case, 40W oil is more viscous than 10W-40. In addition, there is a belief
(not as much as in the past, but still a belief) that 10W-40 does not _stay_
40W at operating temps as the engine hours on the oil increases and gets closer
and closer to oil change time. Transmission do not suffer from dry bearings at
engine startup (as the engine does) because the gears are bathed in oil.