If the autos are so much better why dont all the real class 8 trucks come with autos instead of a manual?
When you stick a truck in gear and it stays there for 8 hours, an auto is wasted money, and unnecessary complexity if the manual options can shed the heat and handle the torque.
A better question would be why do hardly any concrete trucks, garbage trucks, delivery trucks, roll-off trucks or dumptrucks get run manuals anymore? Because in situations where you're actually going to be running up and down through the gears, the manuals are slow, burn up fuel and the driver's like to drop shafts, eat up clutches and blow through shift forks.
I have owned 2 zf-6 trucks and tow heavy alot and have never "melted" one down. My dad has owned 4 zf-6 trucks that usuauly wieghed 36-40,000going atleast hundred miles at a time and never melted one down he probaly had a combined milage of 400,000ish miles on those four trucks with no problems.
You're not putting down much power. I killed my first ZF6 (from heat) in my F-250 at a dyno verified 305rwhp uncorrected Dynojet. Basically flat to the floor with a huge wind load behind me for ~2.5 hours was enough. By the time I finished the return trip it was popping out of 4th gear under power. Pulled the plug and the fluid was black. It was only probably 10,000 miles old.
For reference, that was a pretty well constant 28psi of boost. Unless you're seeing 28lbs steady-state on a single charger, then you aren't putting the power down, and your load is not that hard to pull. Sometimes heavy loads are easy to pull if the aero is slick. Bales of hay and Pickups on 50 inch tires drag a lot of air, and require much more power lb per lb.
Trust me, I would much rather
not have the little wimps falling out from under trucks, but unfortunately they can't hang.
Fwiw, I have made that same trip in my 250 at 40+lbs continuous boost, consuming nearly 20 gallons of water through the injection system to keep EGT in check and my 4R100 gave not one ***...
How many miles does you 550 have on it to have three zf-6s in it charles?
None. Like 255. It had a reman in it when we got it, and I've melted one ZF in it, hopefully the last. I put an additional cooler on it in conjunction with the OEM cooler this past time. I also dropped my interstate speeds considerably. Amazingly, I have to tow SLOWER with the 550 than my 250 so that I don't piss off the fragile little transmission. I've only made a couple hay trips with it and even at slower speed and with the added cooler it already sounds like ground up marbles at low speed because the input bearing is dying.
I just don't have the patience to drive like a total fag on the interstate. If the motor wants to rip, I like to let the big dog eat. Not drive like a puss because my poor little trans might get upset if I break the speed limit.