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-   -   2003 4r70w to tow in OD or not? (https://www.f150online.com/forums/transmissions/520670-2003-4r70w-tow-od-not.html)

Fbird 04-14-2019 03:55 PM

2003 4r70w to tow in OD or not?
This is a well versed opinion, unfortunately not usually resolved.
I have an 03 F150 5.4 4x4. 35's with 4.56 gears and a 5star SCT tow tune. I rebuilt the tranny a couple years ago (thanks Darrin and others) with some MINOR improvements.
My question is I will be towing about 5500 lb trailer for our Boy scouts. MY understanding of my TOW tune is (watching the tach) 1 -2- 3 - CONVERTER- 4th. I have NOT recieved feed back from 5star YET...but working on that end too.

So towing on 4th gear limitations? Is the limitation the bands torque holding ability? or it's line pressure sensitivity due to the lower RPM's ? I realize STOCK stuff will hunt around ALOT per throttle blip ...i can see that killing one but driving with my tune shows it takes EXCESSIVE throttle change for the tranny to down gear. I have no problem towing with the OD button "off" but would really like to know where the issue lies that limits STOCK configuration trannys that dictates NO TOWING IN OD?

Mark Kovalsky 04-14-2019 05:22 PM

Originally Posted by Fbird (Post 5249262)
would really like to know where the issue lies that limits STOCK configuration trannys that dictates NO TOWING IN OD?

I do not know of any limitation that says you can't tow in overdrive. Where did you get that from?

MitchF150 04-14-2019 07:26 PM

I towed a #5000 TT with a 97 F150 with 3.55 gears and 32" tall tires and it was very rare that it would even go into OD.. Going downhill, sure all day long! :) But, even on the flats, it liked 3rd whether I had OD locked out or not.. The computer and the trans pretty much knew what it liked, which usually did not include OD.. Even with a slight head wind, on the flats, you could not even get it to shift into OD... ha, ha! And if it did, once you gave it any pedal it would down shift anyway.

With 35's and 4.56's, it might be a bit better, but in the end, the computer is gonna downshift you if it needs to anyway.

Good luck!


Fbird 04-14-2019 09:10 PM

Originally Posted by Mark Kovalsky (Post 5249265)
I do not know of any limitation that says you can't tow in overdrive. Where did you get that from?

basic owners manual....for ANY truck thats why you have a "tow" button....OD lock out button.....od and towing were NOT configured in stock configuration.

ManualF150 04-14-2019 09:30 PM

Fbird -- Mark Kovalsky worked for Ford on automatic transmissions as an engineer for many years. He'd be the first person I'd listen to before anyone.

With that being said, what Mark said above is absolutely correct.

Only time you use O/D off (or tow mode) is if the truck is constantly hunting in and out of 3rd and O/D. Other than that, it doesn't do anything radically different. Even then, as long as your transmission is properly maintained, you will not have any issues keeping it in O/D for the duration.

Fbird 04-14-2019 10:16 PM

so i c...NOW. That makes sense as the hunting would certainly kill one.
honestly I just glossed over the replies quickly. didn't see the signature. :)

so it's more of a drive and see....... I can do that. Live , ask, learn!

glc 04-15-2019 12:00 AM

This is from the Ford towing guide:

Driving with an automatic overdrive transmission

If your vehicle has an automatic overdrive transmission, towing may cause excessive shifting between overdrive and the next lower gear—especially in hilly areas. If this occurs, we recommend locking out the overdrive gear. This eliminates unnecessary shifting, and can provide steadier performance (see your owner’s manual for more information). If you don’t notice excessive shifting, use the overdrive gear to optimize fuel economy.
From another forum:

Re: Why is towing in overdrive bad?

After all these guesses, do you want to know the real reason why? From a trans tech?.......

First off, the not towing in O/D is limited to certain transmissions and you need to read your owner's manual to see if yours can or cannot tow in O/D. On some Chevy's there is a warning sticker on the driver's door or door jamb area (Mostly up til about '98 or so).

Anyway, back to the real reason. When towing in O/D (we are talking about automatic transmissions only) The engine rpm (which is directly connected to trans pump rpm) is so low that the trans pump cannot pump enough volume through the transcooler to adequately cool the fluid (which is running hotter due to the extra load). So you shift out of O/D to get the engine (and therefore trans pump) rpm up a little higher to allow better flow to the cooler.

The most noted trans that is not recommended to be used in overdrive while towing was the 4l60e used in Chevrolet's. The same trans is still used today, but the no overdrive while towing warning has been removed due to improved transmission pump design.

Even with the old pump design, the only time you really ran into trouble was at slow speeds in overdrive (45-60 mph). If you were towing down the highway at 70 mph the engine rpm was high enough even in overdrive that the trans pump spun fast enough to cool the ATF.

All the heavier duty transmissions used in the 2500/3500 series trucks had no problem whatsoever towing in O/D, by the way. This problem was mostly restricted to light to medium duty trucks and suv's.

Re: Why is towing in overdrive bad?

Ayuh,... In General,...
A transmission in Overdrive is running thru a jackshaft to achieve overdrive..
That builds Massive amounts of Heat...

In Direct, it's running Straight thru the box,...
Much, Much less Heat,+ Wear...

In Drive the transmission components are locked together. The output shaft is locked to the engine crankshaft, therefore it's turning at the same speed. The transmission isn't doing anything.

In Overdrive the output shaft is turning faster than the input shaft (that's why it's called "overdrive"). This requires mechanical interactions inside the transmission (gearing, bearings, etc) that generate heat. The heat destroys the properties of the transmission fluid, which then destroys your transmission.

It's very obvious if you have a transmission temp gauge (measures the tranny fluid temp).

What does that tell me? You need to monitor your transmission fluid temperatures and possibly add an auxiliary cooler.

Fbird 04-16-2019 11:46 AM

excellent info and feedback guys! learning more everyday. Now only 1 question I can't seem to find out (without getting dirty...lol) anyone know what size/threads are on the FORD tranny cooler?
I want to either add an auxiliary or remove original and replace with a larger one. I am NOT a hose clamp kind or person....I would rather utilize quick clip nipples or inverted flare...but thats just me.

glc 04-16-2019 01:57 PM

From what I've heard, if you want to replace the stock cooler with a better one, one from a Super Duty will fit.

Fbird 04-16-2019 03:28 PM

looks like the 6.0L 2003-2009 is the one everybody "upgrades" to

still need to see about adapting lines but...that is NOT difficult

Darrin Burch 04-17-2019 08:25 AM

Originally Posted by Mark Kovalsky (Post 5249265)
I do not know of any limitation that says you can't tow in overdrive. Where did you get that from?

I see overdrive bands SMOKED on reverse drums actually warped from towing in overdrive. I have a suspicion that it's from hunting.

So I tell my customers to get friendly with the OD button and haven't had further issues. I tell them to take it out of OD before they actually start to pass or climb a hill, then get settled in on flat ground before engaging it again. I've got people towing WAY more than they should and so far so good.


Fbird 05-01-2019 08:43 AM

Probably the No. 1 thing i instantly noticed with the "tune" is once you get in O.D. ....cruising....you need ALOT of throttle input for the tranny to get back on the converter..which = ...alot less "hunting" during loaded moderate conditions. (it might feel like stepping on a wet sponge due to the lack of rpms BUT..you get nothing for free)
No. 2 ..the BRAKING action of the tranny.....help CONSIDERABLE

ManualF150 05-01-2019 09:01 AM

Speaking of engine braking... I know the SD with the 6.7 PSD has that feature.

I'm surprised Ford hasn't implemented that on the gas variants using the valves. Kind of like a Jacobs brake.

Lack of engine braking on gas vehicles with automatic transmissions is another reason I am looking forward to upgrading to a F-Series with the 6.7 PSD - just for that feature.

I just hate "coasting". I've been driving stick for so long, I expect my vehicle to radically slow down without the use of the service brakes, especially with a load.

Fbird 05-12-2019 07:35 AM

talking about temps....
Just installed a 40k GVW tru-cool plate cooler (removed my original towing cooler) and installing a temp gauge ON THE TRANNY OUTPUT line ...at the radiator (just before it inters the top of the radiator) what kind of temps should i be looking for. (i will be doing a write up of my install to post a thread) I will be pulling almost 7k trailer thru the foothills in NC. (02 scab 4x4 geared and tuned, 4r70w)
The "thumb" rule i have been seeing on line ranges from outside temp + 100 degrees to..."200 is DEATH" i realize there are many locations to pull temps from and this creates havoc.

Darrin Burch 05-13-2019 08:03 AM

With the quality of fluids what it is today, 200 definitely isn't near fatal. But, with the right cooler, you should stay below that. Towing will definitely raise temps because the converter is going to remain unlocked a lot.

So see what you get and report back.


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