Towing boat at 105 degrees-- O/D Off?

sjpitts

 
 
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I have started to use my 93 FJZ80 to tow my boat. It is not a big boat, under 3000 lbs with trailer. But I am in arizona, where it is hot, and the trip to the lake is pretty much a slow steady climb. It is mostly a highway trip at 55-60 MPH.

My question is, when towing under these circumstances should I turn the overdrive on the tranny off?

My thinking is that turning the O/D off makes life easier on the tranny, but that the higher RPM's could increase engine temperatures. Is that a correct assumption?

On this trip, I turned the O/D off and didn't have any temp problems. The gauge never rose, and the AC never turned off. Given that, I am inclined use this approach---tow with the O/D off, and keep it at moderate speeds. Would you guys agree?

Jared
 
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sjpitts said:
but that the higher RPM's could increase engine temperatures. Is that a correct assumption?Jared
Higher RPMs do not necessarily mean higher temps. Higher RPMs increase flow of coolant and fan draw through the radiator, increasing cooling ability. Unless of course you are are towing a 40' boat uphill at 5000 RPMs. I pulled my 27' Formula with my prior Cruiser in 100+ degree Texas heat with zero cooling issues.
 
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For a given load on the engine, higher rpms should result in lower engine temp due to increased coolant flow and increased air flow due to higher fan speed.

However, torque converter locked up in OD should lower tranny temps compared to unlocked. Does your torque converter lock up in lower gear if you disable OD? If your transmission is constantly shifting in and out of overdrive then you should disable overdrive. If your engine is lugging in overdrive then you should disable overdrive. Otherwise, if engine is not overheating, and engine is not lugging, and transmission is not bouncing in and out of overdrive, I would leave it in overdrive.

3000 lbs is not a huge weight to tow. If you really want to know what is happening, you need accurate aftermarket gauges to directly measure coolant temp, engine oil temp, and transmission oil temp. Only then will you actually know if you are approaching an overtemp problem or not. It is possible to overheat a transmission without overheating the engine. In any case, your factory coolant temp gauge is not very useful for monitoring actual engine coolant temperature.
 

IdahoDoug

 
 
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O/D off, fresh tranny fluid, clean cooling system, clean air filter and good oil. Floor it. You have a tranny temp light that will come on if it gets in the danger zone. Mine's never come on with a boat weight twice that.

DougM
 

e9999

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Arya Ebrahimi said:
O/D off. Hell I usually don't turn O/D ON until I'm at or above 60mph, around town it's off.

Ary
this to lower your mpg intentionally? :D
 

Scamper

 
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Not to be the contrarian, but I tow my trailer with O/D on all the time. I never have had a CEL related to the tranny overheating, nor have I ever had a problem as a result of this. Granted, I don't floor it when I take off, and most of my hauling is on the interstates where I get lockup without any problem. Once I get on the interstate, I usually stay locked up until I exit (or hit a traffic jam). I also change my fluids on a regular basis and use full snyth all around. So what's the potential damage I'm doing by using O/D?
 

cary

 
 
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A few others mentioned, but didn't make clear that there is a difference between having your truck shift down to third under throttle and manually shutting off the overdrive. On the 95-97 trucks, if you manually shut of the overdrive, the torque converter will lock up in third gear. With the overdrive switch on, the tranny will not do this. Given you have a 93, you will have to see if it does this or not.
 

landtank

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If you want acceleration turn on the power switch....oh wait a minute, you have the inferior tranny.
 

sjpitts

 
 
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There is a power switch on my 93. Although it is labeled something obscure, like ECT. I am not really sure what it does. I think it just changes the shift points.

Should you turn this switch on when you tow?

I am not sure if the 93 tranny has the lockup feature-- does anyone know the details?

Jared
 
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Jared is asking what reduces the strain on his engine and tranny, towing in overdrive or in third gear. Well, regardless of whether or not you have a supercharger, it requires the same amount of torque to propel the truck at a given speed, in a given gear, with a given load. Under the same overall load, the strain on the trannies is the same for both supercharged and non supercharged engines. Under the same circumstances, the strain on the supercharged engine is a bit more, as in addition to propelling the load, the supercharged engine has to also drive the supercharger.
Right?
 

e9999

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Rich said:
Jared is asking what reduces the strain on his engine and tranny, towing in overdrive or in third gear. Well, regardless of whether or not you have a supercharger, it requires the same amount of torque to propel the truck at a given speed, in a given gear, with a given load. Under the same overall load, the strain on the trannies is the same for both supercharged and non supercharged engines. Under the same circumstances, the strain on the supercharged engine is a bit more, as in addition to propelling the load, the supercharged engine has to also drive the supercharger.
Right?
prolly better to say the same amount of *power* at a given vehicle speed etc.
the torque at the engine could be different depending on speed, i.e. rpm, i.e. what gear you're in. So the argument that a lower gear (higher rpm) would be better cuz of higher fan and water pump is probably generally true. In reality, I guess higher rpms would also mean higher friction losses in the engine at the same power out, but that's probably not a very large effect. Incomplete combustion etc could also be a factor.
 
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