today was the first day that i towed heavy with my '05 big horn (i
definately bought the right truck!). when i switched into tow/haul mode it
stayed in drive a little longer, but it still shifted into overdrive. is
this normal, or is tow/haul just a setting to keep the torque converter
unlocked or something?
Normal. In '05, the tow/haul mode changes the way the transmission shifts
(keeps the T/C locked longer, extends gear ranges, and will downshift to
assist in braking), but O/D is not locked out. With the 48RE, it's not a
In '04.5, (and '04 as well, I believe), they simply renamed "O/D OFF" to
"TOW/HAUL", because less-than-informed buyers would say, "well, the other
maker has a tow/haul thingy on their transmission - do you?"
It took them damn-near forever, but I'm fairly certain the '05s can accept
an ECM flash to allow approved, warranty-covered use of an exhaust brake.
That might be something you want to look into if you plan on pulling heavy
through the mountains.
pretty much what i thought. what would it take to make an '04.5 perform
like the '05? a controller swap? a flash?
what do those typically sell for? initially i really wanted an exhaust
brake but since playing with my prodigy im confident in its efficient and
effective braking. if its not ridiculous id probably add an exhaust brake
but if its ridiculous ill rely on my prodigy.
That's the only one that's warranty-approved (for whatever that's worth),
but I've always ben partial to PacBrake. The big downer for me about the
Jacobs is that it uses a vacuum pump to activate it. While that in itself
isn't a big issue, the fact that the vacuum pump mounts in the accessory
drive, and therefore requires a special, longer serpentine belt, could make
emergency replacement an issue. The solution here is to get two belts at
the time of install, and keep one under the seat.
BD Power and Banks are also popular choices for exhaust brakes.
the PCM boosts line pressure in 'tow'
since line pressure is up, it takes more governor pressure to move the shift
so shifts are firmer and delayed a bit
converter should lock in OD or in 3rd if OD is cancelled, in 'tow' mode
On Sun, 10 Jul 2005 12:42:49 -0600, "Nathan W. Collier"
if you are talking about an exhaust brake, the '04.5 will not be
approved by dc for one. the '06 auto is approved for one. the '05
will be but it will take a while, probably some time next year. the
software for the '05 has to be written for the ecm and dc is simply in
no hurry to do that. the ecm in the '04.5 is not large enough for the
software and likely can not be changed out, it is a whole different
that doesn't mean that you can't put an exhaust brake on an '04.5, you
just void your warranty if you do.
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