Towing in Overdrive ? - Fiberglass RV

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Old 01-29-2010, 03:03 PM   #1
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Does anyone know (in general) if it's normal and safe to tow in overdrive with an automatic transmission that is equipped with overdrive lock-up torque converter? I do know NOT to tow in Overdrive with an auto tranny that does not have it.

I was reading about the new 2010 Hyundai santa fe. It has a new V-6 engine and transmission with overdrive lock-up torque converter and 3,500 tow rating. Thanks in advance.

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Old 01-29-2010, 04:28 PM   #2
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Most torque converters lock up and unlock when there is a strain on the system such as going up a grade that is why the manuals that are included with the vehicle advise you of not using overdrive in hilly situations while towing.

Our Silverado has a “Towing” button that prolongs the shifting of the gears in order to give the vehicle more power and time to get up to speed.

I will use the overdrive towing on the flat and level, keep it out of overdrive on minor grades and shift it to the next lower gear when towing in extreme hilly conditions.

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Old 01-29-2010, 06:17 PM   #3
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Darwin, we have a Silverado with the towing gear button, too. I apologize for being so DUMB, but I don't even know what overdrive is. Is that when you just have the transmission set to "Drive?"

What do you set it to to get it out of overdrive without shifting down to 3rd?

Blushing at my ignorance....
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Old 01-30-2010, 08:19 AM   #4
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Yes, use your tow button and when it starts to shift in and out of OD to much, Put it in 3rd.

By the way, All Sharon’s are smart as a whip, just my daughter Sharon and she will confirm that.
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Old 01-30-2010, 09:11 AM   #5
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Darwin, I can't tell you how much I appreciate your solving that mystery for me!

We have actually been doing what you described, and it seemed to do pretty well on steep hills, but I wasn't sure we were doing everything we were supposed to.

Funny about your Sharon! I sometimes think I feel a stroke of brilliance, but the dumb times do a good job of keeping me from getting a big head!
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Old 01-30-2010, 08:46 PM   #6
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I am not that familiar with other vehicles so my comments are specific to GM's.

Most GM pickups and SUVs, except heavy duty trucks, have a 4L60E transmission. It is a 4-speed automatic with a Torque Converter Clutch (TCC), commonly know as an 'overdrive'. The TCC gear ratio is 0.7 (nominaly). The TCC is controlled by two solenoids driven by signals from the Powertrain Comtrol Module (PCM), a TCC engage/disengage solenoid and a TCC Pulse Width Modulated (PWM) solenoid. The purpose of the PWM solenoid is to make the shifts from one gear to another less harsh.

In the Non-tow Mode, TCC engage (upshift) occurs when vehicle speed is above 42 MPH and is dependant on speed and throttle angle. TCC disengage (downshift) occurs at a throttle position angle of 60 degrees, independant of speed.

These conditions vary when in the Tow Mode because TCC Engage only occurs when in 4th gear (Drive). In the Tow Mode upshifts for 1-2, 2-3 are delayed and upshift for 3-4 occurs at about 50 MPH. PWM duty cycle is increased to provide, as GM describes them, crisper shifts.

I have designed and installed on my Escalade a relay system that allows me to overcome the shortfalls of the 4L60E transmission, such as frequent TCC disengae/engage cycles when towing with the Cruise Cintrol engaged and downshits to 2nd gear when towing up moderate inclines.

This relay system provides driver control of the following:
1) Locking the TCC engaged or disengaged.
2) Controlling 4-3 downshifts and 3-4 upshifts.
3) Locking TCC engaged in 3rd gear.

This system allows me to tow with Cruise Control engaged for long distances without the TCC disengaging and the transmission downshifting eliminating a great deal of wear and tear on the transmission.

CD and Joyce Smith - Lily, Violet, and Rose
1999 Casita 17' SD - "The Little Egg"
2007 Escalade - 6.2L V8 - 6L80E Trans - 3.42 Diff
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Old 01-31-2010, 11:01 PM   #7
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Our TV is a 2007 Dodge Dakota Quad Cab, with auto tranny and FWD.

In 2008 we drove to So Cal to buy our 17' casita, and towed it back to WA.

The Dakota "tow" button works differently from the above posts, in that, when the "tow" button is set, the tranny will not go into overdrive, period.

The best part of this setup is that when going down a mountain, the tranny will also not go up into OD, so it acts as a compression brake, thereby minimizing the need for using the brakes.

Even on level ground it will not upshift into OD if the tow butten is set.

Even going up over the Syskiyou Summit in So. OR. it rarely dropped down into a lower gear, and never dropped lower than 1 gear lower. Coming down the summit, we rarely needed to use the brake pedal.

We have a lot of issues with some of Dodge's production decisions, but we love the way the Dodge "tow/haul" button works.

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Old 02-01-2010, 07:40 AM   #8
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only with a stiff tail wind. I burned out a tranny once and now always tow in 3rd. I do slow down some to conserve fuel.
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Old 02-02-2010, 09:33 PM   #9
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I am from the old school. I recall that OD was a direct linking of the engine to the drive wheels thereby preventing the mileage reducing drag of the Torque Converter.

Of course I remember Ramblers with the starter button at the full clutch depression.

I had a 1957 2 dr Dodge Coronet with a Red Ram V8 and a two speed auto push button transmission. That thing got all of 6mpg!

Ah, memories!

A charter member of the Buffalo Plaid Brigade!

Whether you think you can or think you can't, you're right.
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Old 02-03-2010, 08:44 AM   #10
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Our old diesel Jimmy had a bunch of transmission failures over the years I used it as a delivery vehicle pulling a cargo trailer -- but this was just factored into the cost of doing business.

Later after retirement I had another transmission failure near Los Angeles. A shop that specializes in Blazers & Jimmys used for rock climbing did the rebuild and set it up to tow reliably in overdrive. What the technician did was to alter the programming it so I can only use about 1/3 throttle in overdrive before it initiates a down shift.

This works great for protecting a weak automatic transmission, but doesn't allow the diesel engine to develop its high torque into low RPM that makes such an engine so convenient to tow with. So I consider the rebuild/reprogramming just OK, but certainly not great.

One must realize that us folks that tow small trailers do not provide a significant customer base that a special vehicle can be designed specifically for our needs. We have to make do with vehicles that are either just marginal for our purpose (such as the various small pickups and vans) or are complete overkill such as the Cummins, Duramaxes and Power Strokes that handily pull ten thousand pound fifth-wheels.

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