Very good thread guys - thanks for the replies and interesting reading...
It's a 97 GMC K1500 Suburban - don't know tranny codes or axle ratios off hand... I live in eastern Washington and talked to a tranny shop owner who says he frequently rebuilds trannys of people who drive over Snoqualmie Pass and abuse their overdrive. Having had my last Suburban tranny rebuilt, I tried to learn what I could from that experience. In my own observations, the ones who are asking for trouble are those who leave their cruise control set at 70mph up a grade and just sit there on the way up conversing with passengers, as the tranny kicksand out of passing gear (3rd), as the vehicle tries to maintain that cruise control speed setting of 70mph up the grade. From what I now believe to be true, that's definitely a tranny killer so I'm now generally kicking the cruise control OFF during those uphill occasions and settling back to a comfortable climbing speed of
55-60mph when climbing a fairly steep grade. I think experienced drivers know when they're putting their vehicle at risk and increased stress by kicking it in the butt with passing gear and forcing it to maintain that 70 (or better) up a steep hill. All that said, I don't want to end up in a tranny shop again if I can ever avoid it in this lifetime... lol
I don't know a lot about how torque converters work (lock vs unlock) and how that impacts the hill climb but a big question I *have* had is, if I'm going up a grade starting in overdrive at the bottom of the steep grade and as my speed slows, depress the accelerator gently to get it into 'passing gear', is there any reason at that point that I can't just pull the transmission handle into 3rd gear (while in 'passing gear')? I would normally DO this while holding my constant speed and without letting off the gas. So in essence - for a given speed, just pull the tranny handle into 3rd to get it out of OD and save the transmission. OR... does it matter? In other words, if I'm climbing the grade at a comfortable 60mph, no cruise on, engine temp is good, at approx 2300 RPM in overdrive though 'passing gear' that we've hashed about, is there indeed any difference?
thanks again guys for the replies... It's very informative. :-)