Why is towing in overdrive bad?

[izoomie]

I've read many posts here that say Don't tow in overdrive.

I think we're talking about a manual transmission here, right? If you're locked in high gear you can break something. (I blew 5th gear in my jetta towing a boat that was too big)

I believe an automatic transmission will take itself out of high gear if it needs to. Of course if you are going up a long hill and it's hunting between OD and the next gear down, you should take it out of OD, but otherwise it's not an issue.

Also I know there are good and bad automatic transmissions out there. This is just "In General"

Comments?

 

[Bondo]

Re: Why is towing in overdrive bad?

Ayuh,... In General,...
A transmission in Overdrive is running thru a jackshaft to achieve overdrive..
That builds Massive amounts of Heat...

In Direct, it's running Straight thru the box,...
Much, Much less Heat,+ Wear...

 

[BaileysBoat]

Re: Why is towing in overdrive bad?

No engine braking in OD. Excessive shifting= wear. Higher transmission temps caused by high vortex flow in convertor = failure.

 

[BaileysBoat]

Re: Why is towing in overdrive bad?

Ayuh,... In Direct, it's running Straight thru the box,...
Much, Much less Heat,+ Wear...

Good point.

 

[nlain]

Re: Why is towing in overdrive bad?

The no tow in overdrive is with an automatic trans, you will destroy the transmission. If you have a manual transmission and engine enough to haul the load without lugging I think you can tow in any gear you want to. I have a 1994 model truck and on flat land I tow in od, they told me that the constant up/down shift would tear it up and as long I was in flat land I would be ok, I guess I was cause I am still going at 240,000 mi. The newer vehicles say do not do it at all, newer engines develop more torque than the older ones and will destroy the trans.

 

[45Auto]

Re: Why is towing in overdrive bad?

The newer vehicles say do not do it at all, newer engines develop more torque than the older ones and will destroy the trans.

The torque of the engine has nothing to do with it. The reason is as Bondo said earlier, it's simply because of heat:

In Drive the transmission components are locked together. The output shaft is locked to the engine crankshaft, therefore it's turning at the same speed. The transmission isn't doing anything.

In Overdrive the output shaft is turning faster than the input shaft (that's why it's called "overdrive"). This requires mechanical interactions inside the transmission (gearing, bearings, etc) that generate heat. The heat destroys the properties of the transmission fluid, which then destroys your transmission.

It's very obvious if you have a transmission temp gauge (measures the tranny fluid temp).

 

[smokeonthewater]

Re: Why is towing in overdrive bad?

It also depends greatly on the vehicle.... read the owners manual.... I tow with my 99 f-350 in o/d at up to 80 mph with a 26,000 lb gross weight.....
I have just over 300,000 miles on it and am on the second transmission...... I can live with those numbers

 

[robert graham]

Re: Why is towing in overdrive bad?

I pull my boat to Florida with my Buick Roadmaster and it's in overdrive most all the way, unless it shifts to 3rd gear going up a hill. My transmission has an auxiliary cooling radiator up front, part of the "towing package" that came on the car. It's no problem at all, engine temperature never even rises. Maybe you refer to a smaller front wheel drive vehicle?

 

[lrdchaos]

Re: Why is towing in overdrive bad?

It also depends greatly on the vehicle.... read the owners manual.... I tow with my 99 f-350 in o/d at up to 80 mph with a 26,000 lb gross weight.....
I have just over 300,000 miles on it and am on the second transmission...... I can live with those numbers

Like stated...it depends on the vehicle. Most gutless gas engines, need to have od locked out if there is excessive shifting. My Ram 2500 cummins, never shifts out of od, and there is no reason to pull it in drive, way to many rpms and to much fuel consumption. Plus it's rated to pull the weight in od.

 

[SuperNova]

Re: Why is towing in overdrive bad?

After all these guesses, do you want to know the real reason why? From a trans tech?.......

First off, the not towing in O/D is limited to certain transmissions and you need to read your owner's manual to see if yours can or cannot tow in O/D. On some Chevy's there is a warning sticker on the driver's door or door jamb area (Mostly up til about '98 or so).

Anyway, back to the real reason. When towing in O/D (we are talking about automatic transmissions only) The engine rpm (which is directly connected to trans pump rpm) is so low that the trans pump cannot pump enough volume through the transcooler to adequately cool the fluid (which is running hotter due to the extra load). So you shift out of O/D to get the engine (and therefore trans pump) rpm up a little higher to allow better flow to the cooler.

The most noted trans that is not recommended to be used in overdrive while towing was the 4l60e used in Chevrolet's. The same trans is still used today, but the no overdrive while towing warning has been removed due to improved transmission pump design.

Even with the old pump design, the only time you really ran into trouble was at slow speeds in overdrive (45-60 mph). If you were towing down the highway at 70 mph the engine rpm was high enough even in overdrive that the trans pump spun fast enough to cool the ATF.

All the heavier duty transmissions used in the 2500/3500 series trucks had no problem whatsoever towing in O/D, by the way. This problem was mostly restricted to light to medium duty trucks and suv's.

Next lesson with be on exactly what the tow/haul switch does, if anybody is interested....lol

 

[bowman316]

Re: Why is towing in overdrive bad?

yea, what does that switch do?

I think If you have a bigger engine, then you can make it up a hill in overdirve. SO you don't need to shift out of O/D.
My f-150 has a button on the shifter that takes it in and out of overdirve. sometimes i will put it into D to get some engine braking when slowing down.

 

[roscoe]

Re: Why is towing in overdrive bad?

Next lesson with be on exactly what the tow/haul switch does, if anybody is interested....lol

Well,,,,,,,,, don't leave us hanging here.

 

[bruceb58]

Re: Why is towing in overdrive bad?

On GM trucks it raises the shift points. On the Ford F-150, the button is called OD off and just doesn't allow the tranny to get into overdrive.

 

[bruce40]

Re: Why is towing in overdrive bad?

OK SuperNova, what exacly does the tow haul mode do?? I bought a fiberglass boat last year, much more heavy than my old alum. boat, and i started using the tow/haul mode in my 05 silverado. The only diff i noticed is the rpms climb up higher before it shifts.

 

[smokeonthewater]

Re: Why is towing in overdrive bad?

that will be a loooong answer if it is correct because it does different things on various trucks

 

[Jeepster04]

Re: Why is towing in overdrive bad?

Far as I know on our Jeep all it does is turn MDS off, keep it out of 5th gear, and move the shift points up.

 

[skargo]

Re: Why is towing in overdrive bad?

I was told in my owner's manual to not use OD in my 47re trans in my Cummins powered Dodge. Of course, since my truck has been seriously upgraded in power (550/1100 at the wheels) I had a full on trans built. It has billet input and output shafts, upgraded pump, etc, etc, etc. It will pull uphill all day long in OD with no ill effects. It also performs flawlessly in truck pulls and drag races too.
Not bad for an 8K lb truck that gets 18+mpg daily driving.

 

[TheLucille]

Re: Why is towing in overdrive bad?

The Dodge autos had other problems, I know one of them you couldn't idle for extended periods of time because the transmission pump didn't pump! Bad for other reasons (like wetstacking and emissions as well)

Tow/haul mode depends on the tranny; I know on my Allison it not only increases the shift point rpm a bit, but locks the T/C so there is less slippage/heat. The Allison is pretty smart, probably other things going on with fluid pressure behind the scenes.

 

[skargo]

Re: Why is towing in overdrive bad?

Dodge stock trans are no better or worse than Ford or GM, the only people that say they are bad, don't drive them, which I find peculiar. Having worked at a multi make dealer, I know the parts departments kept the same amount of transmissions on inventory for replacement purposes.

I made a bone stock(other than me turning the line pressure up) Dodge trans last over 100K miles with some stout upgrades to the truck.

FYI, the Allison is no better than Ford or GM's offerings either, it's just marketing genius, people hear Allison and assume it's the same trans in the big trucks.

Anyone with towing questions should defer to their owner's manuals just to be safe.

Edit* one more thing I did for my trans was to add a Torque Convertor lockup switch. I can set where it locks and unlocks, and it also automatically unlocks for up and down shifts. it also allows me to have my OD off(light ON) when I start driving, and it automatically turns my od on(light OFF) when I hit a preset speed, typically 55mph. I try to keep my Cummins in it's most efficient powerband(2150rpms) and the controller helps a lot. Also gives me a semblance of engine braking, without a jake brake.

 

[dorelse]

Re: Why is towing in overdrive bad?

I tow my boat with my 1998 Dodge Ram 1500 4x4 all the time. (46RE trans)

I'm in IA and it doesn't do a lot of shifting out of OD as its pretty flat terrain. I added a trans temp gauge on mine when I put on a extra capacity aluminum trans fluid pan. My trans temps never get above 160 degress, and I do have the tow package, before the trans pan upgrade, I do believe mine got quite hot.

But yeah, on mine, if the truck is in park, I don't believe it pumps tranny fluid, which is why you check the levels in Neutral.

120k miles, no issues, shifts great, tows great.