Originally Posted by macgyver
I think what you'll run into is not burning your clutch out so much as stripping gear teeth from the gears internally... I've seen it happen in pickups, volkswagen bugs, cars, etc...
There's a reason they've got a maximum rating... The strength of the internal components is the factor here... Not your clutch. You could be shifting from 1st to 2nd and the shock of all that weight on the tranny might even bend the internal guide rods, crack gears or simply shatter them...
I guess my thinking is whats different from the shock (aka load) vs a hot rod driving under high aerodynamic load for instance, or a drag racer using full throttle massively exceeding engine torque ratings for a transmission because they aren't doing it very long.
The only load the transmission should be seeing is the torque of resistance on the output shaft. And say changing from say 6.18 gears to 3.08 gears with the same chassis would double the forces and resistance on the transmission all else being equal. Or for that matter driving at 70mph instead of 50mph is about double the aerodynamic load, and that's a constant load, instead of a more temporary load which weight is while accelerating (unless youre on a grade). So I guess i'm making a few assumptions like the typical light truck is expecting to bomb up grades at full throttle usually and should have a fair bit of safety measure. I mean aren't I right that most GVWR are basically a guess from the engineers typically assuming worst case conditions?
I can fully see breaking gears if you are climbing uphill with double the rated load with the foot to the floor all the time. But once the load is moving isn't it basically static except for aerodynamic resistance?
I'm also curious about what the difference is between the load placed on the back instead of the front, an SM465 is designed to take 400lb/ft basically all day long from what I understand, even in granny gear.
Am I wrong in saying "its fatigue from the constant LOAD that breaks the gears, not the weight" and thinking weight should be more flexible as long as you arent worried about grades and are mostly flat towing? (or using limited throttle/power, not full throttle, on any grade you meet even if it means going 25mph) And shouldn't the load on the output shaft and through the gears be directly determined in proportion with my right foot? (I mean I should think in my mind that an SM465 would move 1 million lbs for the Shuttle Orbiter, if I had 6000:1 ring and pinions in the axle because the axle load/leverage is what you are actually resisting afterall)
(a part of me has always just wondered about things like why the transmission torque rating is say 457lb/ft last year and this year is upgraded to 468lb/ft, those differences seem so miniscule I have to wonder who computes or decides them based upon what formula or simulation or what the improved weak point is that made last year's model 11lb/ft different)
I suppose if there's room I could stick a big rig transmission under there but I wouldn't know how to hook that up to the engines i'd usually find in busses without spending 10x as much for an adaptor plate. :P This line of thought is because i'd seen a pair of manual transmission gas engined busses with tranny quirks for sale in the area and I know the SM465's are cheap for swaps and give alot of gear in 1st.