Well I have yet to melt a Zf 7 down...
My dad has put 400,000 probaly on zf6 towing everyday and never melted it down and a 30' gooseneck 873 bobcat and 8 pallets of 1500-2000 lbs sod must not be much weight behind a 1 ton in your eyes. I personally know of more 4r being replaced on stock or just chipped trucks then a zf-6 but I shift gears for a living so what do I know
You are not putting down much continuous power DUMB.... ASS.....
You can hook a truck to a 100,000lb load if you want, and if you drove 1mph nothing would EVER get hot...
OR.....
Take a truck making 400rwhp and with it COMPLETELY EMPTY, go lay it to the floor and start making laps around Talladega and you will melt down the trans, u-joints and rear carrier bearings if you don't get off the power soon enough.
The load alone means NOTHING!!! It is the combination of weight, speed and terrain that determines the stress to the trans. Or.... these variables are all wrapped up in one neat little value... POWER. In my experience, the truck needs to be steady-state at ~300rwhp to push the ZF beyond it's happy spot.
99% of all 7.3's don't EVER even MAKE 300rwhp on the best day of their lives. Much less do they then drive down the road flat-out, pulling that power.
Last year I slowed from 70-75 down to 60-65 and the trans seems okay on the two runs I made at that speed. Just that little bit of speed change made a world of difference because of the dramatic change to the continuous power required.
If you let the truck lose speed on hills..... again, MASSIVE amounts of power can be consumed on hills. I have completely consumed 600+hp on hills, towing with my 250.... no pedal left down there simply MAINTAINING speed...
Point being.... 99% of the time, guys with a story like yours above have a truck that puts down 250rwhp in the hottest program they have, with the stars all aligned and perfect conditions. Then they take off towing in their "tow" program, which doesn't even make that..... THEN.... they drive down the road at half pedal because they can't keep EGT in check....
Go write a program, and set up a 7.3 that makes 300+ rwhp ON THE DYNO, then go lay it TO THE FLOORBOARD for 2 HOURS and let me know what that ZF6 has to say.
10:1 odds you couldn't even put together a 7.3 to MAKE enough continuous power to melt a ZF without running excessive egt and killing itself in the first place.
Maybe some of you should focus on that. Can your engine even MAKE 300+ for hours on end? That might be step one in understanding why you don't have trans temp issues...
:doh: