Towing in OD w/ 3.55s

[w123suv]

This is in an E350 IDI N/A ambulance van. Previous owner swapped 4.10 axle for a 3.55. It works well when not towing and it worked ok with a small 2k travel travel but now I've been using it to tow a larger travel trailer i believe around 4k (21ft). It does ok but as soon as I hit any tiny up hill we slow down.

It's annoying but even if I can live with it, am I hurting my transmission by doing so much shifting in and out of overdrive and/ or towing in overdrive in general with that gear ratio. I have done the TC manual override switch and if the hill uphill is small or short I will just unlock the torque converter and that usually does. Is that a bad idea?

Thanks for your thoughts.

 

[Powerstrokin350]

Sounds like it's doing what it's made to do, I would probably only use overdrive on flat ground, but once you hit the hills I'd shift it out of OD so it wasn't doing the back and forth shifting. That's how I run my wife's '03 PSD when towing our gooseneck, but my gooseneck is an all steel double deck sheep hauler from the '70's, probably weighs 7k lbs empty, one heavy SOB!

 

[laserjock]

X2 Drop it out of OD on the hills and watch the trans temp gauge.

 

[FORDF250HDXLT]

you don't need to manually lock out od if you dont want to.if the TPS is set correctly it'll kick into 3rd for you quickly under load.sounds like it's working as it should.it shouldn't try and go back into od too soon.it should take until the load is light enough again.if so,the trans wont be "hunting" between gears.don't mistake a downshift for hills/loads gear hunting.

the only thing your hurting by unlocking the converter,rather than letting the trans downshift for the lighter hills,is probably fuel economy.your manually telling the trans to loose it's direct connection between engine and trans for a semi-type of gear split.i suppose it wont hurt anything,but there's nothing wrong with letting the trans unlock the converter,kick down into 3rd and relock on it's own either.

in short,you can just let the auto be an auto if you want.
of course 3.55's wont tow as well as 4.10's will but 4.10's suck the fuel down needlessly when not towing too.gear ratio's are a trade off.there is no one perfect set.

 

[w123suv]

Thanks guys. I thought maybe the higher gear ratio was putting more strain on the transmission internals but it sounds like i don't need to worry about that. As far as fuel economy I read on one of these forums that the fuel economy was not that much better than with 4.10s simply because as you guys are saying you have to take it out of overdrive so much. If I had 4.10s would it allow me to stay in OD most of the time? If I have to go up much of a grade even without towing I have to take it out of OD. Is that normal?
This is the only 7.3 diesel I've owned so I don't have anything to compare it to. Sounds like you guys are saying stick with what I have for the fuel economy? I tow the trailer with it greater than 90% of the time so if it towed better I wouldn't mind losing a little fuel economy when not towing. BTW I have been getting 18-20 MPG not towing and 12-13 with the camper.

 

[drinkypoo]

The 3.55s are best for highway economy.

 

[Andertusa]

I'm not trying sound *******, but the factory tells you to NOT tow in Overdrive.

 

[drinkypoo]

I'm not trying sound *******, but the factory tells you to NOT tow in Overdrive.

Sure, but what's it going to actually hurt if you're not hunting? If the trans can't handle the load, it'll downshift...

 

[Andertusa]

Well, I'll admit the factory tends to overstate the obvious, but they really don't know what we'd be towing. To them, a small pop-up camper is the same as a 18,000lb gooseneck. They don't have the common sense to see the difference, mainly because that common sense was SUED out.

 

[trackspeeder]

I'm not trying sound *******, but the factory tells you to NOT tow in Overdrive.

Actually you can tow in overdrive. The E4 is designed to do that.

The only time you should take it out of OD is when its hunting.

 

[Andertusa]

The towing while in OD thing is completely new to me, and technically, you probably shouldn't. An OD is great if your engine is powerful-enough to muscle things along; the engine in his( the O.P.) truck obviously isn't up-to ***** for handling towing while in OD. If it was, it wouldn't need to downshift until there was a REAL incline( like 10-15%, and for a long distance). The rear gears are taking away the engine's mechanical advantage.

 

[trackspeeder]

You can tow in OD all day long. Will not hurt the tranny. The key is when to drop a gear. If you're on hilly terrain. Lock it out before it hunts. You see a hill ahead, push the button, before you hit the grade. Descending is the same deal.

Winding it up in third not only creates heat, it kills your fuel economy.

 

[mikepotts]

i just looked at my owners manual and it states that towing in OD is fine with the E4OD, NOT reccomended with the AOD.