6.0L Power Stroke Engine and DrivetrainDiscussion of the 6.0L Power Stroke diesel engine and drivetrain in the 2003-Up Super Duties and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 6.0L Power Stroke engine.
Today I decided to try out my tow haul button on loaded just to see what happens. I just wanted to see if this sounds normal, its an 04 by the way. It holds the gears until 2300 to 2500 rpm and from first to second shifts kind of hard maybe torque converter locking up?) then from there it gets alot smoother. Then when you are doing 40 mph and let off the gas completely t coast, it coats then downshifts quick and kind of drags the gear to slow you down. Just wondering if this is normal or not. Thanks.
Sounds pretty much the same as mine. The gear down feature really saves on braking. If I understand correctly there is a connection between tapping the brake peddle and the down shift pattern but the manual is not completely clear on this. maybe another poster will join in and explain it.
The Tow/Haul Mode raises the transmission pressure to keep the transmission from shifting in and out of overdrive (it's called Hunting) when pulling loads while at crusing speeds. Tow/Haul also assists in saving the brakes by downshifting and using the engine to slow the vehicle down, kind of like an engine brake.
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2005 F-350 Lariat, 4x4, FX4, 6.0 PSD, TorqShift, 373, CC, LB, SRW, Tow Command, Camper pkg., 325/60-18 Toyo Open Country AT on factory rims w/ no lift, Permatech sprayed bedliner, Fumoto Valve, Bright Box w/ Fog light control, KC Daylighters mounted as aux. back-up lights, Zoodad mod, ISSPRO Guages (EGT, Turbo Boost, Trans, Oil & Water Temp and Volt Meter), AirRaid Intake, Muffler delete on factory pipe, ARP headstud & SCT Xcal 2... So far!!!
Tow/haul does not raise transmission pressure. Pressure isn't what shifts an electronic trans, it's the PCM that makes it shift.
Tow/haul changes the shift schedule to make the shifts at higher RPM and to prevent shift hunting. The torque converter will only lock in the two higher gears.
Tow/haul also has a downshift braking feature. It looks at acceleration rate, throttle position (it has to be closed throttle,) brake lights, and the brake pressure switch. If the truck is at closed throttle and accelerating the trans will downshift. If it sees the brake lights, it will downshift again. If it sees the brake pressure switch, which means you're fairly hard on the brakes and it's still accelerating, it will downshift.
All of the downshifts will delayed if it would make the engine overspeed.
__________________ Mark Former Automatic Transmission Engineer 1988-2007
What RPM'S should be regerstering when in tow-haul and downshifting on downgrades? Ive seen it hit 4000 and higher (scary)!!
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2006 F-550 DWR, LWB, CC, XLT,AUTO, Banks 6 Gun, Big Boss exhaust, Banks EGT guage, Cb, Chariot Custom Hauler Bed, Garmin GPS, "WHITE ALL FORD", I Love this BEAST!
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Automatic Transmission Engineer 1988-2007
Linear Mode
