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Old 01-28-2022, 03:14 PM   #1
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Mixed messages on overdrive towing.

some folks i talk to say always tow out of overdrive.

others say its fine to tow if the trans is not shifting in and out alot...

so what is your opinion ?....
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Old 01-28-2022, 03:20 PM   #2
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With the Allison I just put it in "D", leave the OD on, and let the electronics handle it. I do turn on "Tow/Haul" and the exhaust brake.
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Old 01-28-2022, 04:26 PM   #3
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Tow/Haul and you won't have to ponder it.
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Old 01-28-2022, 04:29 PM   #4
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Originally Posted by WagonMaster View Post
With the Allison I just put it in "D", leave the OD on, and let the electronics handle it. I do turn on "Tow/Haul" and the exhaust brake.
Ditto here. Shifter in "D". Tow haul on. Exhaust Brake on.

"M" mode will allow me to set the max gear and even downshift before a hill, but I never use it. The Allison TCM logic suits me just fine.
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Old 01-28-2022, 04:48 PM   #5
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I'm not a mechanic so take my opinion for what it's worth. On an older diesel non-Allison I had, the tow mode blocked out the OD. I think the newer Allisons just change the shift points for heavy loads. I have to admit I have occasionally forgotten to turn on the tow mode and it really doesn't make much difference I can see. My normal travel mode is tow and exhaust brake on. I think you would need to really try to hurt your Allison so I wouldn't spend a lot of time worrying.
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Old 01-28-2022, 05:40 PM   #6
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I towed heavy with a Ford E4od that everyone said you couldn't tow in overdrive and it had the original transmission at 220k miles when an employee rolled the truck. The manual in my 2018 GMC with Allison said you only need to use tow haul at or near max gcwr.
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Old 01-28-2022, 05:59 PM   #7

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I overthink/overdo it.

I have a 2009 Dodge Ram 3500 dually. It has the 68RFE, this is before the Aisin trans was available. I did some reading about it, and then more importantly spoke with 2 knowledgeable diesel mechanics I know and Sun Coast transmissions. They all agreed that OD when pulling a 15-16k fifth wheel down the road while putting the engine under heavy load, could eventually shorten the trans life (for this particular trans, others maybe not so much). The mechanics and I drive by feel. Downhill or cruising along level, I'll use OD. Uphill or into a headwind, I tend to lock out OD. To put it into something simple for the DW, I suggested she keep an eye on the boost gauge. 8ish PSI or under use OD, above 8psi in boost, lock out OD. That's the number I noticed when I perceived the truck to be working harder. Probably over analyzing, but it's working okay for us so far.

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Old 01-28-2022, 06:27 PM   #8
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Well, YMM please

Originally Posted by sumjoe View Post
some folks i talk to say always tow out of overdrive.

others say its fine to tow if the trans is not shifting in and out alot...

so what is your opinion ?....
Very vehicle dependant on older models. Most newer ones just set tow/haul and use OD. Some transmissions have up to 3 or more OD gears nowadays. This is what owners manuals are for.
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Old 01-28-2022, 07:30 PM   #9
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Like kdauto says, with many recent model year vehicles you don't have to worry; they have 8 or 10 speed transmissions and the electronics will control the tranny fine. On the old 4 and 5 speed trannys, they put in a torque converter that tends to unlock when under a little extra load; this produces slippage and heat that can damage the transmission. You might say it was an old-school 'faux half-gear' meant for short term extra torque. On these older units you'll see the engine RPM climb maybe half as much as an actual gear change, and that is when the converter is unlocked. Manually locking out overdrive basically prevents this behavior in the torque converter.

Some people might try to run in OD and only use lockout if they notice slippage. I say, how can they be certain they'll notice every time there is an unlocked converter? It's easy to 'zone out' of engine RPM when there are other things to think about (traffic, upcoming curves, scenery, the pretty gal you saw last night, etc). Why take chances with the tranny, just to maybe save a buck or two worth of fuel?
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Old 01-28-2022, 10:39 PM   #10
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It really depends on what engine you have, your final drive gear ratio, the gear ratios of the transmission you are using, the weight of the load you are towing, the wind direction and velocity, and the terrain you are towing on. With my 2021 Powerstroke/10 speed with 3.31's I lock out one or two overdrive gears on certain occasions.
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Old 01-29-2022, 06:38 AM   #11
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I haven't used tow/haul yet. But I'm towing mostly on flat land right now.
Owner's manual says to use tow/haul IF the tranny is shifting a lot.
When that happens, I'll make the change.
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Old 01-29-2022, 07:06 AM   #12
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Run it in D on the shifter and tow haul. Also run your exhaust brake in auto (if you have one). I have towed in OD in my 97 F350 PS, 06 Dodge Ram 3500 CTD, and my 17 F350 PS. I never had a trans problem. My 17 F350 I tow my 41 Ft fifth wheel in OD with the CC set at 70 mph. No issues
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Old 01-29-2022, 08:13 AM   #13
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I just put it in TH, engine brake and go. This is a new pickup so I am still learning, but that is what the manual says.

My previous Duramax, a 2002 2500, I just used D and TH as no engine brake was available, but when EGT's reached 1200 I would force a down shift to bring the temp. down. I towed everything from a big stock trailer to a 32' Holiday Rambler to my current 38' LXR Nitro toy hauler without any issues using that method.
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Old 01-29-2022, 08:49 AM   #14
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What is your tow vehicle??


IF tranny is shifting in/out.........that builds heat/heat kills tranny
Downshift to stop the tranny 'hunting'

Tow/Haul......when towing/hauling
Is it time for YOUR Medication or Mine?
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