I have a new mark lt 4x4 5.4,3.73 and I have just put my 7x12 cargomate enclosed trailer behind it with 2 harleys inside,it is tandem axel and I cannot get it to stay in OD except when on flat land going 60 mph,if i speed up to 70 it will not shift back into OD or when I go slower than 60 it will not stay in OD but yet my last truck(99 f150 4x2 LWB 4.6,3.08 gears) Towed the same trailer and stayed in Od at all speeds above 55 mph,granted my trailer is 18 inches taller than topper on pickup but it was 2 foot taller than 99 f150.
I called dealer yesterday and they know of no fix for this. Any Info appreciated ! Upset in Delaware

 

Don't tow in OD. Your owner's manual states not to do so if the transmission hunts gears.

 

Absolutely do not tow anything in OD. That's a gas saving gear for cruising on the freeway, not to say that you can't use it on city streets. On the newer superduties it's called "tow gear". It's the same as turning off the OD on the smaller trucks. It keeps you in a lower gear and a higher rpm so your engine and tranny work easier.


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Mods to date:
Procharger P1-SC 9# boost, 275rwhp, 336rwtq.
42# inj.
90mm MAF.
4:10 gears.
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3" Flowmaster exhaust SIDO.
MB Motoring Precise 20" Chrome wheels.
P285-50R-20 Eagle GT's.
Autometer engine oil temp, tranny temp gauges
mounted on A pillar.

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Not really. OD is no weaker than first second or third and can handle the weight just fine. However, constant hunting between OD and 3rd depending on the load and road conditions is bad b/c of the massive heat build from locking and unlocking of the torque converter.

The 03+ 6.0L powerstrokes and 05+ gasser superdutys with the 5R110 tranny have a tow haul mode similar to the allison automatics that when activated uses a completly different shift strategy and computer logic. Not a simple lockout of the OD gear like the 4R100, E4OD, and 4R70w.

Adrianspeeder

 

constant hunting between OD and 3rd depending on the load and road conditions is bad b/c of the massive heat build from locking and unlocking of the torque converter. [quote]


That is why you don't tow is OD! It's for maintaining a cruising speed at a lower rpm. When towing, you need to maintain higher rpms, it's easier on the tranny.

 

So lock out overdrive. That's what that little button on the shifter bezel is for. Mine hunts for gears whenever I'm towing my flatbed trailer up a slight grade.

 

If it's not hunting in and out of OD, then USE IT!!! Be smart about it. If you're going up a hill, into the wind, etc, and you notice you keep popping out of OD, then maybe you should lock it out. Just my $.02