tow mode/transmission question

Fred G. said:

Tow switch or OD switch is pretty much the same thing. My 2000 Dodge Dakota actually read "OD on/off" at the end of the shift lever. Some trucks read tow or haul on/off. It does the same thing. It keeps the OD to kick in when the motor is under load or under 45mph.

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Not so! When in tow/haul mode, the 2005 shift points in lower gears are all changed completely, staying in the lower gear longer. You are correct in that it doesn't go into OD when in tow/haul mode.

in tow/haul mode on my 2008 Chevy Duramax with the Allison, it will go into OD if you are driving fast enough. The owners manual states to put it in Drive, select tow/haul mode and drive it. The tranny really is remarkable.

56kz2slow said:

They are not the same on the new trucks I have driven and that my friends have.  I've test driven several new and fairly new Fords and Chevy in the last few months.  The tow-haul mode, as explained in the owner's manual and by the brochure says it changes how the transmission shifts, but not what gear it is into.  The default D position is includes the Overdrive, sometimes shown with a D in a circle. The one below depending on the year and number of gears will be a D with no circle or 3rd, sometimes 4th on a transmission with more than 4 gears is with the Overdrive off.

If you re-read the post I put earlier, the guy does a good explanation of the difference between the two.

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I forgot to mention that the newer trucks or vehicles, have "multi-gear" trannys as opposed to older models that had designated gears. Now the trannys work on a type of hydraulic system that thru various sensors, it determines how much torque is needed to move the vehicle at the lowest rpms the engine can handle.

I have a 20002 GMC 2500HD, (8.1L gas) but with Allison tranny. The owner's manual (and invoice) call it a 5-spped trans but yet there are only 4 selections on the column. Anyone know what that 5th gear is?

I have only had this truck for a coupla months, one long camping trip to mountains in Va, I was not at all pleased with the perfromance but think it's more me than the truck as I surely do not understand how best to utilize the Allison while towing.

I can only comment on a 1500 4x4 6.0L GM truck, but Marc got it right -- which is basically to say, play around with it and see what works.  With my '07 4x4 1500 GMC 6.0L (vortec max) I tow a trailer that is roughly 7700 lbs loaded (truck is rated for 8500).  The truck will go into O/D when in tow/haul mode at highway speeds (ie: 60-65 mph) on flat surfaces -- no problem.  However, in the hills the trans is constantly shifting in and out of overdrive.  To be safe I keep mine in tow / haul but out of overdrive --- unless I have a few miles of flat surface.  The RPM's are higer but the truck pulls a lot better and the tranny isn't shiffting all the time.  Trans temp is also a few degrees lower this way -- although not much.  I also change the trans fluid about every 25-30k miles.  Hope my experience helps.  BTW -- next time I'll buy a 2500 or 3500 so I never have to worry as much about the tranny.  Lots of miles to go before I trade my little vortec max in though.

"D" - Drive - is actually two gears, overdrive (5th) and drive (4th). The selectable gears are D, 3, 2, 1

I realize this thread has been inactive for more than the 120 days but from what i've found is most closely associated with my question with those that most likely would know..
I have the 2007 Ford V10 on my Voyage 35A... transmission is the Ford 5 speed with OD and also the "Tow/Haul" switch on the shift handle..
Going to do Yellowstone and tetons this summer so expect to find some up and down slopes... will do hywy 14 and 16 from SD and then around yellowstone...
Only inclines/declines I've been on so far was hywy I65/I24 going thru Tn/KY and one bad experience going up lookout mountain on very narrow steep road that made the brakes very hot on way back down...
I found that using OD with cruise control on is a bad idea going into hills/mtns...when it drops down, rpms jump to 4800rpm and sound like engine will fall apart.....
I took the cruise off and  found that the "Tow/Haul" gear handled just about anything at 3200rpm or lower and stayed above 58mph.....  Learned that it will do fine and am comfortable with engine at 3200rpm - suspect speed will drop to less than 55 in some real mountains but so be it....
The question is really about going downhill - engine braking..... on the downhill of I65/I24, only once did the "TowHaul" gear need additional foot braking to stay under comfotable speed....
Wondering however when I get in some real hills in west,
Brakes are ABS but the manual for this unit says it also has some kind of an "intelligent braking system" - not sure whether that's something in actual braking system or affiliated with the engine braking.... Will the "Tow/haul" gear provide enough engine/transmission braking going down the longer/ maybe steeper declines or will I likely have to shift down to 3rd gear on way down  (therefore plan on it to begin with) ...
Have the Mountain west and mountain east books so it's obvious I haven'y really been in the "mountains" yet with this........

Fred G. said:

Tow switch or OD switch is pretty much the same thing. My 2000 Dodge Dakota actually read "OD on/off" at the end of the shift lever. Some trucks read tow or haul on/off. It does the same thing. It keeps the OD to kick in when the motor is under load or under 45mph.

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Incorrect.  My 2001 F350 has a 4R100 transmission, the end of the stalk has the OD on/off button.  When you lock OD out (off) it will not allow the truck to go into OD so it keeps it in 3rd, my 2004 has a torqueshift tranny with the tow/haul button, the transmission changes shift strategies but spends most of it's cruising speed in overdrive, it doesn't lock OD out, there is a huge difference between the two. The tow/haul mode on the newer trucks also aids in engine braking a little bit differently, it doesn't kick in until you either hit the brake or if you have the cruise on it will kick down.  The OD on/off system includes a lot more driver input.  I've had several ford vans and trucks that were gassers that I used to have to pull trailers in and around the eastern mountains of Maryland, PA, Tennessee, KY, Virginia, Wva and I would not use the OD off button until I was climbing a steep hill, then i'd shut it off when going down to conserve fuel.

I would say on my Allison transmission it really depends on the situation and the load I am towing. Probably is the same with any other tow vehicle and trailer combination. Also the 5 speed Allison I have in my Chevy 2500HD has a button on the shifter that does both in terms of Tow/Haul Mode and OD on/off. If you push the button quickly it turns the Tow/Haul mode on and off. If you hold the button in for a few seconds it turns the OD on and off. I find with the Duramax and Allison I can leave the OD engaged with no issues and no transmission overheating pulling a 10,000 lb. GVW trailer; however I always engage the tow haul mode when towing because it does improve the performance uphill and downhill. Not needing to turn off the OD I think is due to the engine torque of the diesel, subsequently the transmission doesn't shift  much on uphill grades. On steep downhill grades I will manually shift down if necessary to preserve my brakes. I suppose if I was towing a 3,000 Lb. popup I would not need the tow haul mode engaged either. If I was towing the maximum 13,500 Lb. rated trailer for my vehicle I would probably turn off the OD and engage the Tow/Haul mode.

In line with this topic, does anybody know how the use of a computer like an Edge Evo in tow mode would change the use of the factory tow mode?  My Tv is a 04 GMC 2500HD and a 12,500lb load almost always in tow mode, except when I forget to turn it on.  Now I have an Edge Evo installed which I put in tow mode for pulling...I got to wonder if it would conflict with the factory tow mode.

Simon

repcool said:

In line with this topic, does anybody know how the use of a computer like an Edge Evo in tow mode would change the use of the factory tow mode?  My Tv is a 04 GMC 2500HD and a 12,500lb load almost always in tow mode, except when I forget to turn it on.  Now I have an Edge Evo installed which I put in tow mode for pulling...I got to wonder if it would conflict with the factory tow mode.

Simon

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I have an Edge Evolution on my 01, it works well for towing, gives you a few more ponies and a lot more torque but you are still going to want to use your trucks tow/Haul button.  It changes shift strategies in the transmission a whole lot differently than your Evo does and the truck's computer will still adjust once it realizes it's pulling a trailter to so you get all the benefits of the trucks computer and the programmer.