At what weight should you use tow/haul mode on the allison trans? Some say all the time and others say 75% of ratings. What is everyones opinion?

I run it almost all the time, loaded or not. I like the fact that the upshifts are later, but do it mostly because the Torque Convertor is locked above about 20 mph in 2nd and above. Normally it only locks in OD at about 50 mph and above. Less trans fluid heat when the TC is locked.

GM recommends using T/H when GCVW is at 75% of max GCVWR. That's about 17,500lbs.

But you can use it when ever you want.

I tend to use it when accelerating in city type traffic towing.

I've towed the my crew cab, 4x4 dually and a 10K trailer! I only use it when I'm at a load where the tranny can't figure out what gear to be in and starts going in and out of top gear, or when I'm going up and down steep grades! I've got 50k miles all towing and I hardly ever use Tow/Haul! I suppose I'm wrong, but no problem here! The ally has always acted perfectly! Am I missing something again?

I'd say your missing the added braking in traffic that the ally in t/h gives. Slows the load without using up your service brakes ....far better control. Also for hill climbs the t/h tc lockup keeps the ally cooler and not slipping, extending the life of the tranny and fluid. If you tow flat interstates t/h won't make a big difference. I much prefer the behavior of the rig with t/h on and this is "only" towing 6500lbs. As another poster put it so well " for towing the D/A is a beast " Amen.

I tow trailers for a living. When there is a trailer connected to my truck the tow/haul is engaged. I want the torque converter lock to prevent slippage. I believe it helps keep the tranny heat down and prevents slippage which leads to loss of fuel economy under load. It helps breaking and keeps from loading up the engine at low rpm because it will shift at higher rpm and speed and will keep the tranny in a lower gear in city traffic which is higher rpm.

I also love the OD lockout switch. My 01 didn't have it but the 03 does and it is great to be able to lock out OD when on a pull and the tranny doesn't shift because there is some much power that it keeps the tranny just above the shift point. On some long grades in the desert in CA and AZ my truck will hang on the edge in OD and the engine and tranny temp will start increasing. When it goes more than I want to see it go I can lock out the OD which raises the engine rpm and maintains the speed. This lets the eng and tranny cool down some.

Ford owners only wish theirs worked so good.

Tom Cobb