AH64ID

Actually yeah, he got more that 150 from a 60K tranny....

ECT and Tow/haul raise the shift point so you make more power in each gear... The alison tranny you speak of is an excellent tranny, it knew to downshift to help with compression braking.....Its is also available on the 8.1L.. Tow/Haul isnt more than reprograming to keep a few extra RPM in each gear, it works the same with or without a load.. and once in a gear nothing is different...

I dont understand your being hurt on a slight hill, please elaboriate.....

In my family we have 2 toyota 4runner autos, 2 chevy autos (1 4L80E, and one 4L60).. they all work about the same, OD above 25-30 if you are not on the gas... not what is best for the tranny or fuel economy...

And in town for me too is stop and go to 55-60, but I keep it out of OD if it looks like I will not reach 45 or more before slowing...

And lastly, OD when towing... My dad has a 454 suburban with a 4L80E that he has done some towing of a full 4horse with. He has a tranny temp gauge in it.. Around town it never warms up, when towing a full trailer at fwy speeds it run great in 3rd (D), but if he goes to OD it warms up considerablly so he only uses it on super flat and down hill... The truck has more than enough power to drive all day in OD, the RPMS are fine, but it still likes D better... unfortuantly a tow/haul mode wouldnt do anything for this.....

I still beleive that it is best not to use OD in stop and go and under 45mph..

trythis

> relevant to an active tow/haul feature: I meant that the tranny (while towing) being in OD wouldn't hurt anything (as in overheat, or lug the engine) while going down a slight grade so it was noce that it wouldnt stay in D all the time. I wouldnt want to be in a high gear on a steep grade while towing, but it seemed silly to be coasting down a gradual hill in D and having to mash the peddle to go down a hill when OD would let it engine brake at a useful speed.
That make sense? I am kinda groggy,

My GMC's Tow/Haul mode was operating on some sensors. If I used it when the truck was emty and not towing, it shifted normally regardless of the button being pressed or not. If I hooked up a trailer leaving it running so the button stayed on, it dramatically changed the shifiting. This was a 2002 Z71 that I don't have any longer, but that tow haul mode was active in sensing loads. I tried it towing and hauling a big pile of rocks in a quarry even, just like the commercials, well, no cowboy boots.

regularguy412

I like to keep the ECT 'on', when in town. The few extra RPM's give a better feel and provide more driveability. Again, this mode allows the engine to operate closer to what seems to be its most efficient RPM range.

Mike in AR

Bumpin' Yota

yall with diesel swaps, just remember for highway mileage, the lower your RPM the better milage you will get, even if that means driving more slowly. This is why you'll often see diesels only doing 65mph in a 70. The savings in MPG is substancial compared to most gassers....

AH64ID

Yep, espically tuboed engines, its funny as boost goes up mileage goes down, even faster..


I didn't realize that about tow/haul.. all the ones I have driven work just like ECT even empty. And I thought of something on my drive in this AM, my 03 doesnt have ECT anymore.... But it does like lower RPM's a bunch more than my old 3.0 auto and the 3.4 autos I have driven... Between 40-50 around here is when OD becomes a useful gear, its pretty flat and I cruise the backroads to work and usually do 50-60.

We generally shift into OD on downgrades, unless its so steep we are now braking.... but the engine does like a break from turnig D RPM's... But now my old man has a cummins 610 with a 6speed for the horses, manuals are SOOO much better for this type of stuff...

subprime

YES BRAIN FART!!!

Thanks to everyone that chimed in on the subject.!

ebelen1

Thanks to those that posted. I've only had manuals in the past and the only auto I've had (last car) did not have OD. I've had the truck for a year now and have kept the OD and ECT on constantly. I do mostly city driving w/ one big hill a day and about 2 miles max on the freeway (top speed is 65 mph).

I decided to turn off the OD for the city driving after reading this thread and the auto shifts much smoother. It could be in my head. Is it just in my head? I'm also interested to see if mpg go up or down w/ this setup.