Towing with OD off.

[dodge man]

Mine is a 5 speed automatic.

 

[Reg]

I have a tow mode and a OD off mode on my 2007 Dodge. I think the tow mode just rasise the shift points while the OD off mode holds it out of 4th and 5th gear, but I'm not sure.

You can use tow/haul mode for "pulling" and O/D off mode on downgrades to provide engine braking.
Least ways, that is how I use mine.
My Durango limits itself to the bottom 3 gears when in tow/haul mode, which I dislike.
I prefer the Allison, which gets into top at about 57 when lightly loaded, higher if I am treading on it hard.

 

[carpenter383]

Well put. "Overdrive" is simply any ratio between the engine speed and transmission output speed that is less than 1:1. Some of the higher count automatic transmissions have more than one "overdrive" gear ratios.

Another big contributor to heat generation is an unlocked torque converter. In top gear and a heavy load you will often notice that the transmission will unlock the torque converter to allow the engine to rev slightly higher where it can make more power. This works great as a short term solution, but if you are hauling a load it may stay ulocked for longer periods which can generate a lot of heat energy. If the transmission is locked out of top gear, it will not need to unlock the torque converter nearly as often because the engine is already revving higher where it can make more power.

Also, the clutch packs which are used for top gear are sometimes marginal in strength, ie GM 4L60 transmissions. When high inertia (high GCWR) shifts from 3rd into 4th are made it wears the 3-4 clutch packs significantly. This is also avoided by locking out 4th gear ("overdrive").Using a "tow/haul" mode often influences the lockup strategy of the torque converter, another reason to use it when appropriate.

Actually in the 700r4/4l60e/4l65e the 3-4's are generally the weakest link (aside from the pwm tcc in '95 and newer) the 3-4 clutch is applied when the trans shifts to drive (third) and stays there until it goes back to second. The 2-4 band applies to go from 3rd to 4th, so the 3-4's aren't going on and off from 3rd to 4th.
A side note about 4l60e/4l65e's '95 and later is they wear the tcc valve in the valve body prematurely, which causes the p1870 code (component slipping) and very harsh 1-2 shifts (the computer raises line pressure when it sees this problem). If anyone has a high mileage 4l60e that is shifting really hard after going down the highway it's most likley the tcc valve bore.

 

[JB4310]

Have 2007.5 Dodge Diesel, 6-speed auto. Tow/haul mode upshifts faster, but still will go into overdrive. I use the manual shift, which can be set from 1 thru 6 speeds, 6 being overdrive. By setting it to 5, it will not shift past 5 gear. I'm guessing your truck is not 6-speed? Different trans.?

Yup and I got an 07 Ram 3500 cab/chassis with a different 6 speed (Aisin) with mine in tow-haul mode, upshifts and down-shifts are tighter and it's limited to 5th gear. with OD off it locks out 5th and 6th.
Mine doesn't have the manual shift my wife's Grand caravan calls it autostick.

I rarely/never use OD off but always use tow-haul. My truck is about 12,000 pounds with service body and tools, so even when not towing I'll use tow-haul when descending steep hills. With the factory VGT's engine braking (when turned on) combined with the tight down shifts, the truck stays in total control without using brakes! often I have to get back on the accelerator to prevent it from slowing to much.

With a heavy trailer in tow-haul you'll lurch forward in the seat by just letting off the accelerator, it's awsome! The more weight, the better the braking

JB.

 

[timswi]

If I have a heavy load or a trailer on mine..I run it 3rd gear and tow/haul mode..Makes a huge difference. I don't like to hear the truck strain any more than it has to. When I'm doing this, I couldn't care less about gas mileage. I just want to get back home with the truck in one piece.

Done this with 30+ foot travel trailers and 1/2 ton pick-ups for years with no negative results.

Pulled car trailers and everything else doing the same thing.

 

[Tul01]

Thanks Chris I had always wondered when I was out with him but never thought of it again until I saw this thread.

Brent

 

[jda1961]

i have a 2009 ford f150 with the 6 speed tow haul transmision. i use it a few times for towing, it takes some getting use to. when you engage tow haul it locks out overdrive to give more RPMs for pulling power. plus if you tap the brakes it down shifts and stays in that lower gear til you hit the gas, works very well on icey roads or back roads where you don't want to ride the brake. i had a 2002 F250 with the manual 6 speed before this truck, i'd choose the auto over the manual, just a slick trans in my oppinion. i get great fuel milage too, about 21 mpg. and with a 5.4 V8 thats not bad.

 

[FlaDon]

On early Allison 5 speed equipted trucks, there was no OD lockout from the factory. GM came up with a switch to take care of that. That being said, running with GCWRs of 10K to 18K, I have never had the tranny get hot on the highway in Tow/Haul and Cruise Control turned on. The tranny will drop into 4th on its own. First up to 3200 RPM and then if not loaded down, 2800 RPM at 65 MPH. One of the things you need to factor in is tire sizes and rear axle ratios. A truck with stock tires and a higher numerical ratio rear axle will hunt less than the same truck with oversize tires and a lower ratio. Two trucks with the same size tires, one with a 3.73 and the other with a 4.10 and the same loads should see the 4.10 shifting less.

 

[Diamondpilot]

On early Allison 5 speed equipted trucks, there was no OD lockout from the factory. GM came up with a switch to take care of that. That being said, running with GCWRs of 10K to 18K, I have never had the tranny get hot on the highway in Tow/Haul and Cruise Control turned on. The tranny will drop into 4th on its own. First up to 3200 RPM and then if not loaded down, 2800 RPM at 65 MPH. One of the things you need to factor in is tire sizes and rear axle ratios. A truck with stock tires and a higher numerical ratio rear axle will hunt less than the same truck with oversize tires and a lower ratio. Two trucks with the same size tires, one with a 3.73 and the other with a 4.10 and the same loads should see the 4.10 shifting less.

I wonder if this was the reason I seen overheating issues of the Dmax I had? I was always led to believe it was the air intake that was the issue and they redesigned it the next year but they also went to the 6 speed Ally. I was towing 12,000# and 15,600# with it.

Chris

 

[carpenter383]

The allison 6 spd has 2 overdrives, both 5th and 6th are overdive. A 5spd can be converted to a 6 spd with a valve body and tcm change, but it's pretty darned expensive.