I haul a fairly heavy camper @7000 pounds with my '06 F350 V10. While I have generally used the Tow/Haul transmission position, find that it does nasty things to my gas mileage, i.e. 1 to 3 mpg less. The owners manual is not particularly good with explanations (good reading if you are a 6 year old) so what my question is about is what are the implications from not uasing that position 100% of the time while hauling. A death notice to my trans? Or....? Yes, I will use it if it is hilly, but flat or mildly rolling roads, with the amount of torque that a 3 valve V10 generates seems to make this overkill in most cases and with gas hovering at $3/gallon, is it really necessary. Watching the trans temp gauge this past weekend didn't indicate any higher readings then without any load. What does the Tow/Haul position really do - lock out overdrive? change the torque converter vane position? (you're right I'm durn engineer and like to know why )

Essentially, its to take stress off of your trans and gives you engine braking. It is a trade off, fuel mileage for trans life.

blacksnapon said:

Essentially, its to take stress off of your trans and gives you engine braking. It is a trade off, fuel mileage for trans life.

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In other words, keep up what I'm doing but have enough sense to drop it into Tow/Haul on hills. To give up 10 to 30% on the gas mileage score is tough to swallow - it only has a 28 gallon tank!!!!

I did note that there was significant engine braking out of Tow/Haul going down hills yesterday which surprised me. And I still don't have a clue as to how it's accomplished mechanically/electronically - and am still curious. Is there a decent write-up somewhere?

Kinda curious about that myself...............Never really noticed a diffrence in mileage when I was pulling my trailer (as I have a diesel)............And my truck seemed to have more than enough eumph to pull my 5th wheel out of tow haul (One thing I did notice is that my truck tended to wind up tighter with it on than with it off). So what you're saying is that if I don't use it I'll toast the tranny?

Gunner

What I have done in the past was when on generally flat or gentle grades is I do NOT switch on the tow/haul mode, because there is no need as your transmission is not hunting for gears and there is no need for the braking power of the engine

When I am going on a long pull uphill or downhill I switch it on to kick off the overdrive allowing to go downhill and using the engine to do some of the braking as opposed to my braks and when going uphill it keeps it from hunting for gears.

It should be noted though that I am not a mechanic and sometimes wonder if I am even competent enough to drive a car let alone have a trailer but those are my real world experiences. My trailer was a bumper pull TT coming in at about 9000lbs loaded. I used that technique when towing with an 04 suburban as well as an 06 F350 PSD

My guess is that the Tow/Haul mode is for those who don't have a lick of sense to know that you have to take the tranny out of OD to prevent the many down and up shifts in hilly country nor bother to check the transmission yemperature gauge as overheating the ATF and losing the oil's lubricity is the downfall of the clutchs and bands. It is also a CYA for Ford while the truck is in warranty - mine is gone at 40K but you Diesel owners have that extra mileage length. Like I said above, I'll use Tow/Haul when needed, but use the normal mode all other times - that is unless someone is able to show me that I'm in jeopardy of having a toasty critter beneath my feet.

Interesting - my many trucks and cars have had FMX's, C4's C6's, E4OD's, 4R70W's and now a Torque Shift(whatever number that is) and I have never had a failure hauling up to a 10K# trailer using conventional shifting and common sense.

Dunno about the Ford transmissions, but the Chevy van I drove over the summer ('03 with a 4-speed auto) had a tow-haul mode that definitely did more than cancel overdrive.

It firmed up the 1-2 upshift so much I couldn't stand it unless I was hauling over 1000 lbs, but it made the shifts much firmer when loaded heavy and gave me better engine braking, too. It also made the upshifts more predictable. It would still run through all the gears, unless I manually shifted it.

If it was just a little less agressive, I'd have thought it was great.

My understanding is that the tow/haul changes the shift strategy. It let's the engine wind-up a bit more before the shift. As for the engine braking, I believe it's just keeping the converter locked.

6L PWR said:

My understanding is that the tow/haul changes the shift strategy. It let's the engine wind-up a bit more before the shift. As for the engine braking, I believe it's just keeping the converter locked.

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See thats one of the reasons why I try not to use it. I do NOT like my engine winding up around the 3K RPM range before shifting, especially when my diesel doesn't need that kind of RPM to move the load. Never had any temp problems with my tranny, and never had any problems pulling with it off. I was just wondering if I was tearing something up by NOT using it.

Gunner

it raises fluid pressure internally thats why you feel a firmer shift. also it keeps the convertor unlocked which is the higher rpm's. also there are one way clutches in autos that when the clutch pack is held will give engine braking.

very interesting stuff guys. Thanks for sharing.

Ryan

the tow haul manages to use a combo of locking the converter and down shifting the trans when it feels you applieing a certain amout of brake pressure. this gives you engine braking to help slow you down on grades .but as far as running on flats keep the button turned off.

now as far as the 5r110w tranies i see from the many coming into my shop the forward clutch packs like to fry up when the diesels are turned up to far. another on need item its the billet convertors. you can obtain the same out a newer multi lock up clutch design which has better material in the packs and 2 clutches instead of the 1 the early ones had. and keep a large amount of cash in your pocket for other toys.

lets remember the 5r110w is a fully electronic unit. you can do the same as a custom built unit be just properly adjusting the tranie tuning. there are NO valve body mods to be done as they are just electic solinodes

Ah ok, so I'm not about to cook my transmission by not running the tow/haul when I have my trailer tied on to my truck, then. Good deal. I was about to get worried

Gunner