traveling1253
Maine
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Joined: 04/15/2007
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My '05 GMC Sierra has the 5.3l 4L60E trans and 3.43 gears. I tow with T/H mode on and don't use O/D. With T/H mode it will go into O/D if traveling 60+ but with the 3.42 gears it takes only the slightest incline or headwind to downshift. I figure that the less shifting the better so I just put it in 3rd and leave it there. Runs somewhere around 2400 RPM at 65MPH, 10-12 MPG depending on terrain and speed.
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CliffordG
Central Wyoming
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Joined: 10/01/2009
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Tystevens wrote:I seldom have to manually select the gear when climbing or descending hills with the Allison.
Did you know that if you hold your T/H button in for 3 seconds or so that it will lock out OD ? 
2005 Silverado 2500HD with 8.1L/Allison pulling a 2007 WW FSW 2800.
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LarryJM
NoVa
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Joined: 11/09/2007
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With my 2001 4R100 tranny I always tow in OD and with cruise probably 95% of the time. Now if I see a significant hill in more mountainous areas that I know it won't hold I will cancel cruise and drop out of OD and once it shifts into direct and the torque converter locks up I bury the pedal and try and keep my speed at 60+. Now this is just for my combo and you have to find what works best for you. One thing to remember is I think if you manually select a gear you a locked in that gear and the tranney programs will not be used and then you can cause damage if you exceed what that gear is designed for.
Larry
2001 standard box 7.3L E-350 PSD Van with 4.10 rear and 2007 Holiday Rambler Aluma-Lite 8306S Been RV'ing since 1974.
ALL TRAILER MODS>>ETERNABOND INSTALL>>RAINKAP INSTALL
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itsmike
Greelawn NY, Long Island!!!!
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I have a trip coming up and there will be some nice inclines to travel.. I was just going to turn off the OD and let her scream a little.. Ugh!
2003 Chevy Stacraft Conversion (The Gas Guzzler)
2011 Nissan Sentra SR (The Gas Saver)
1999 Sunline Saturn T24
1 Wife
3 Kids
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Jayco28BHS
16SBH5290970116
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I always tow in tow/haul mode with my Dodge. Figure I am "towing" so it only makes sense. As most have said here, it doesn't always lock out OD but it does move the shift points and changes how long it will hold a gear as I accelerate from a stop or climb a hill. Every vehicle will be diffrent so check that owners manual.
2010 Dodge Ram 2500 Crew Cab 4x4 345 CID
383 HP/403 Ft Lbs Torque/3.73/8800 GVWR
2008 Jayco 28 BHS
Retired USAF
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E&J push'n wind
San Diego CA, The best climate on earth!
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Joined: 12/21/2009
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As far as towing in OD, I'd go with what the owners manual says.
For towing with the CC set, terrybk gives a pretty good discription in this link, best I've seen anyway and I thought I gave a pretty good discription on this discussion in another thread.
Here is his quote if you don't want to click over,
terrybk wrote,
"I use CC all of the time to maintain speed, but the speed I chose depends on the gear. If I am in OD or 3rd (depending on the conditions), that speed is 60MPH. If I have to drop to 2nd, that speed is about 50MPH and I will set the cruise to maintain that. If I have to drop to 1st, that speed is about 35MPH. Again, I will set the cruise to that speed. As the climb ends, the RPMs will start to rise and I will move the lever to the next higher gear and reset the cruise to the new speed for that gear.
However, if I am in the mountains and the speed is constantly changing, I don't use the cruise since it's faster to react with the pedal and shift lever. It often means backing out of the throttle to let the speed come down to the speed that will match the next lower gear I am about to select. Either way, I manage the engine for peak torque if I am in 1st or second. In 3rd or OD, the speed will be at or slightly higher than the legal limit and reving to peak torque will take me well past the speed limit.
What I won't do is allow the the cruise to kick down gears. It's just going to over-rev the engine to maintain the speed which is far too high for the gear. That is just not the way to do it. Pick the speed for the gear and then set the cruise. Be prepared to kick out the cruise if the speed is going to change. You know when a down-shift is going to be necessary, so back out of the throttle to let the speed drop to match the lower gear, drop it down, the RPM's will come up and you can decide if you will be at that speed long enough to justify setting the cruise to maintain it.
We have some climbs where 1st or 2nd will be needed for several minutes, so why not let the cruise hold it there while you relax."
Wisdom is the right use of knowledge. To know is not to be wise. Many men know much, and are all the greater fools for it. There is no fool so great a fool as a knowing fool. But to know how to use knowledge is to have wisdom.
Charles Haddon Spurgeon
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TXiceman
(Near) Houston,TX
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Joined: 11/17/2000
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Run your diesel in OD and use the cruise on flat ground. As soon as the tranny starts to hunt or you start dropping speed, drop out of OD manually.
With a gas engine, I'd be very careful about using OD.
Ken
Amateur Radio Operator.
Vintage 1989 Avion Silver, 34V, toted by a 2002 F350, crewcab dually, 7.3L,4.10 axle,SCMT. Travel with one miniature Schnauzers, one standard schnauzer and one African Gray parrot. Practicing for retirement!
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twaldher
Bremerton, WA
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I'll use OD in my truck, but only if I don't feel the engine lugging down.
Which means I need to be pulling about 75mph to guarantee that.
The upside, I pick up 2-3mpg from 60 in 3rd to 75 in 4th.
Your gas engine ain't whining unless it's wrapped up at 4500 rpms or better. Remember, it's not a diesel and it's power band is often in the 3,000-4,000 rpm range, not 1500-2500.
1998 Chevy Crew Cab 4500 4x4 454, Auto, 4.10 Gears
2003 Nomad M-308 (30', bunks, 14' slide)
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hotpepperkid
Chino Hills CA
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I have 135K miles on my 7.3 with a 4R100 tranny and I always tow in OD but I will lock it out sometimes and I lest it soft shift when Im paying attention to things. I have a mild chip which I have had for 100K miles. gpk
2000 Ford F-350 SRW 4X4 PSD Jayco Super Lite 29.5RKS (31') 5th wheel 50 gal X-ferflow in the bed tank. Banks big exhaust and Stinger kit.
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VirtualGarage
Vancouver, Canada
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Joined: 05/27/2009
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skipnchar wrote:Tow/haul is not even vaguely related to Over drive. One changes the final drive gear and the other simply changes the points where shifts occur. One does not in any way exclude or include the other. Your manufacturers owners manual is the best source of a recommendation because different manufacturers handle the subject differently based on what they know of their own product. Ford, for example RECOMMENDS towing in OD with the exception of a few rarely experienced instances.
Good luck /Skip
In the case of GM, in addition to changing the shift points, the tow/haul mode also increases the rate at which the alternator charges the battery and increases transmission cooling. Definitely, check your owner's manual.
2007 GMC Yukon XL Denali ~ 2010 Keystone Premier 31BHPR ~ Sold: 2009 Tango 289BH
ProPride 3P Hitch ~ RV Modifications ~ Gear & Accessories ~ Road Trip 2010
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