I'm new to the 5th wheel scene and need to know the proper way to use the tranny when towing. I've got a F-350 dually diesel and pulling a rather heavy trailer with a tri-axle set up. When starting out, should the overdrive be off and should I continue driving with it off all the time even at highway speeds? Or, should I start with the OD off and then when I reach cruising speed can I turn it on? I would appreciate some comments as regards this issue. Thanks in advance.
I am not familiar with your truck but many newer trucks, as ours does, have a "tow mode" that you should use when towing your rig. Turn it on and leave it! Perhaps a model year of the truck will help others give you the information you request!
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Maxtar, that depends on the year of your truck. My older truck had an "O/D Off" switch and that's all it did. The newer trucks have a "Tow/Haul" switch that adjusts shift points, engages engine braking and adjusts for pulling weight over running empty. If you have just the OD switch you might want to turn it off unless on the highway. With the Tow/Haul, I turn mine on when I hook up. I know this is a simplification, but hope it helps answer your question.
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RaenMark wrote: Maxtar, that depends on the year of your truck. My older truck had an "O/D Off" switch and that's all it did. The newer trucks have a "Tow/Haul" switch that adjusts shift points, engages engine braking and adjusts for pulling weight over running empty. If you have just the OD switch you might want to turn it off unless on the highway. With the Tow/Haul, I turn mine on when I hook up. I know this is a simplification, but hope it helps answer your question.
It's a 2000 model with no special "Tow/Haul" switch, just the OD option. My brother-in-law (who thinks he knows everything about everything) said I needed to leave the OD off, but it seems to me at the very least once you reach highway speed you should be able to turn it on to get the best MPG possible. I have just been pulling it locally so I am at present keeping the OD off as I am not sure about the whole thing and don't want to damage the tranny. So, until I hear from some of you more experiened RV'ers the correct way to operate the unit, I'll keep the OD off while driving
You can leave OD on. The main reason to turn OD off is if the tranny is hunting the gears up and down. Shifting too much is hard on the tranny. And the 4R100 is not very good at maintaining a gear. Sometimes it comes down to turning OD off in hilly terrain, and leaving it on when on flat terrain.
I leave mine with O/D disengaged when towing... Might be a bit rough on the tranny having O/D engaged especially going up and down the hills. Disengage it when towing... DOnt know if that is OFF or ON so I use the term DISENGAGE IT.
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My two cents: I have 2003 F450 7.3 and I turn OD off on down hill grades and starting out. Once at highway speed I engage OD. Seems to run smoother, quieter and less RPMs. Gas milage improves. Perhaps I am doing it wrong?
I had a 2000 F350 (Fantastic truck!) and had to have the tranny replaced at 35,000 miles. I was told that towing with the overdrive on was the main reason. I was over a 100,000 miles on the 2nd tranny when I sold the truck and never had any problems with it.
I would definitely tow with it off.
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O/D is the weakest gear (smallest cog) so towing with O/D on can lead to transmission problems.
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