So I was on my way to the beach with my 6000 lb trailer that I have been towing for 2 years now. I most always tow with the OD off (light on dash is on) which keeps me from gear hunting and keeps engine at a steady RPM. At 15000 miles I flushed and replaced fluid with Mobil 1 synthetic and at the time of problem I had just under 28,000 miles.
Back to the story.. about 200 miles into a 600 mile trip, after a stop for fuel, I began merging back onto the freeway, speed maybe 50 ish and I hear a loud bang followed by metal grinding and the truck shaking badly. I though that a sway bar from my trailer or the drive shaft had come out and was dragging the pavement, to give you an idea of the sound. Soon after that OD light begins blinking and TRANSMISSION MALFUNCTION pops up in my odometer.
I pull over and see nothing, leaks, metal etc. As I try to start off again I get about 20 mph and the engine goes WOT yet no speed is archived, I drop into 2nd and gain speed again, tranny slipping. Needless to say I drive the remaining 400 miles to the beach in 2nd gear. Ford roadside won't help me because I can still make forward power and gives me the number to the dealer where I am headed, they say call if I break down completely.
Luckily I make the dealer the next morning and tell them my story, the tranny man on staff says "you towed with overdrive off didn't you?" "Yes" I replied "it says so in the owners manual, towing, heavy loads or hilly terrain use overdrive." "Wrong" says all the service guys in harmony "We see this all the time"
So after a few days on vacation in a rental car the tranny is rebuilt. Final verdict is towing with overdrive builds up pressure in the tranny that the seals cannot hold they blow out. This also caused the clutch discs to wear out over time and when they let go that was the grinding metal I heard.
They instruct me to never tow with OD off unless I am in the mountains let the tranny shift back and forth.
I explained that I have and Edge and monitor the temps which get hotter when the tranny gear hunts. They still backed up what they said and claim the owners manual clearly states not to turn off over drive... funny thing is my owners manual and the 2008 RV towing guide that I picked up at there dealer states "reason to turn overdrive off are hilly terrain, heavy loads, stop and go traffic or towing with a trailer. Thats all it says nothing about only in the mountains or rare circumstances.
So I made the 600 mile trip home today doing it their way, no overdrive except the mountains, tranny temps went from 190-205 range that I would see towing with overdrive off to 225-235 with overdrive on and lots of gear hunting to keep it at 65-70 mph while towing.

Your opinions, no bashing about the weight of my TT it is well under the 8800 lbs that Ford says the truck will tow. 5000 miles of towing with this truck thus far and this is my first problem.

BTW the next day my 4WD solenoids went out and I had to replace them on vacation, under warranty but on the way home they went bad again, only three days old so back to my local dealer Monday morning.

 

Those guys are idiots!! You can't tow a load like that all the time. It's not the gear hunting that's going on...it's the torque converter locking and unlocking and that's what generates all the heat and you can not continue to drive in OD with the converter unlocked. The temps would just keep going, and going, and going...as you saw yourself. Don't ever do that again. Why those guys told you to tow with the OD on is beyond me.

Now...here's my disclaimer. There's nothing wrong with towing with OD on...IF it will stay in OD with the converter locked. Once the converter starts locking and unlocking (the 'gear hunting' you thought was going on), it's time to turn the OD off.

 

Thats what I kept trying to tell them yet they swore by it. So to appease the court I did it there way, now if something else happens I am still under warranty and then I may get the new tranny which is what I wanted in the first place, not a rebuilt one.

 

You better be careful with that one. These guys are telling you something against the owners manual and if they were called to the stand, do you think they'd step up and say "yea, we told him not to do what Ford says so yea, we'll pay for his new tranny"?? If you burn up the tranny to appease those bone heads, the Ford rep is going to ask you why you went against the owners manual and then proceed to tell you you abused your truck and therefore Ford is not liable for the tranny. Think about it.

 

I'm just going to grab some popcorn and a beer and wait for Mark K to see this tale....

 

Man Welfare, seems like every trip out for you there is an issue? Yeah I gotta agree with Galaxy, that cant be right. You gotta think how hard it feels pulling something that heavy with the OD ON. Seems like your pulling with a 4cyl! I too pull something that heavy ive tried with the OD ON and I cant for the life of me feel like its right. The motor and tranny seem like they are working so much harder that it cant be good for the whole powertrain? IDK maybe the book says turn the OD off only on hills, ect. but it just seems less harmfull to me when its OFF.

 

Go with what the owners manual states. These guys are wrong. It sounds to me like they were looking for a way to blame you for what happened. There are a lot of good techs out there but it sounds like you got a couple of ***** looking at your truck that day.

 

The concept is pretty easy to understand if you've driven a 5 speed manual for a while.

Same thing, except instead of you shifting and downshifting the auto does it for you. Easy to bog it down, in 5th, towing heavy through hill and dale.

 

Well I got the word from the dealer today, they are going to replace my tranny and hubs and should be done by Monday next week.
When I pick it up I will ask again this dealers opinion on towing with the OD on or off and see what they have to say.

 

Before asking the dealer, try reading the owner's manual. If they don't agree with what the manual says, ask them why. Do you think they know more about the trans than the people that designed it?

 

Tell us what you really think, Mark - you are the one who designed it.

 

No, I didn't. I was never in the 4R70W design department.

 

I tow a 20ft Triton Bassboat all over texas and when I need the lower gear I turn the OD off, like when I am in around town, starting from a stop, going up a hill, but usually once I get to HGWY speeds and the ground is level I will go back into OD on ...zero issues..

 

DITTO escept my load is a 4x4 rig on a car hauler. Most flat terrains are no issue and OD is usable. But in town and slight hills and such it will start to unlock the converter alot and I just turn it off. I have 42k on mine now and have only had it serviced/flushed once at the dealer just past the 30k mark. So it's got the motorcraft mercon 5 in it still I assume.