Why is towing in overdrive bad?

[SuperNova]

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

Maybe, depends on how minute a detail you want to get into..l...

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.

Yep, and ramps up the line pressure

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!

Flat out wrong.....the trans pump pumps any time the engine is running...nature of the beast and a fact on virtually every auto trans built..

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.

Yes sort of.....it also ramps up the line pressure and it does change the duty-cycled logic of the t/c clutch

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

Once again, wrong. The trans pump is turning any time the engine is running....the concept you are getting confused is the torque converter fill circuit. The reason certain transmissions are specific about checking the fluid in either park or neutral is because one will have the torque converter fill circuit, but not the other. If you aren't filling the torque converter when you check the fluid level, it could give you a false reading. The main difference inside the trans between park and neutral is the position of the manual valve, other than that, the same stuff is spinning or not spinning in either position, also in the park position, the parking pawl is forced into place against the output drum.

As far as the tow/haul switch (this does NOT apply to the O/D OFF switch), all it does is modify the strategies the TCM uses to calculate shift points, line pressure and torque converter clutch engagement. This is an overly simplified explanation, but it gives you the idea. So the tow/haul switch is an input to the TCM which mostly just causes it to alter it's "Comfortable shifting" strategy to more of a "Damn the comfort, we need strength, power and durability" sort of strategy...So you get a little higher shift points, as well as earlier downshifts and you get firmer shifts and more clutch apply pressure. And the torque converter lock-up strategy get adjusted as well..

 

[Jeff-in-PA]

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.

Not all of them. I can leave my 2001 Chevy Suburban 2500 in overdrive while towing. It has the 6.0L with the trailer towing package including trans cooler. Full guages including trans temp.

I don't put in in Tow Mode unless I'm towing my '24 pontoon. The 18' celebrity I/O is light enough it hardly downshifts on the trip to Ontario Canada.

I agree with the "no overdrive" in the case of my previous suburban. It was 1990 1500 with a 350 ci / 5.7L with an aftermarket trans cooler. Towing in OD would cook the trans as it was not designed for that.

So it comes down to either read the owners manual to be sure or just keep it in drive if reading about the actual proper use of your vehicle isn't important.

Jeff

 

[NetMatrix]

Re: Why is towing in overdrive bad?

It all does depend on your vehicle and the tow weight it is recommend for. Like with my 2004 Envoy XUV with a s-speed transmission with over drive (4th gear) I can pull a trailer behind it in over drive if it is at the recommended tow weight of

Weight Carrying: 4000 pounds max trailer/boat weight
400 pounds tongue weight

Weight Distribution: 7600 pounds
912 pounds tongue weight

Now even though my vehicle is at those recommendations if I'm even 500 pounds below the trailer weight and 20 below tongue weight on hill lands I have to put the SUV into 3rd gear. They are right about the heat. The extra heat can cause the gears to bind together, because when metal heats up it expands. Thus causing it to heat up or the gears to even break. Granted like with my vehicle if I drive it in 3rd gear I can't go above 55mph, however taking that extra amount of time to get some where is worth it cause I won't have to worry about any damage to the vehicle.

This right here is just to add in on the examples of why not to pull the trailer/boat in over drive. It's better to be safe and drive slower in that one lower gear than to cause thousands of dollars worth of damage.

 

[bruceb58]

Re: Why is towing in overdrive bad?

SuperNova,

I have a 1999 1/2T Silverado. Were the low fluid flow issues fixed by then? The 1999 model came out really early because that is when they changed body styles. My rule of thumb has always been put it in the gear that kept it from hunting between gears but had never heard of the temperature problem due to low fluid flow.

I really liked my 3/4T Suburban with its tranny gauge in the dash. Does the 1/2T tranny have similar provisions already there that allow you to read temp? Do you know if the tranny temps can be read over OBD2 on the 1/2Ts?

 

[skargo]

Re: Why is towing in overdrive bad?

I know when I worked at a Dodge dealer, the techs there told me to put my trans in neutral for a minute or so when I started it, don't recall exactly why. I know with the stock trans if I threw it right into drive, it would sometimes slip. If I let it sit in neutral for no more than a minute, it never slipped.
Not sure on the why, I took apart a TH350 once years ago, and almost went nuts trying to figure it out hahaha

 

[Parts Jimmy]

Re: Why is towing in overdrive bad?

Read the owners manual. My truck has a 4R100 OD trans. If I did not use OD my truck would get terrible fuel millage. Ford says to use OD. My truck has right at 250k miles on it. I had the transmission rebuilt at 210k because the splines stripped on the input shaft. The builder showed me old clutches that looked pretty good. I will continue using OD.

 

[JaseBosto]

Re: Why is towing in overdrive bad?

I have a 2003 Silverado with the 4L60E and towing. Did they fix the pump issue by then? If I tow through hilly terrain I usually put it in (D). A V8 might not need to do that but my 6 does. On flats and slight inclines it won't shift out.

 

[F14CRAZY]

Re: Why is towing in overdrive bad?

A manual transmission shouldn't care. I've towed my Bayliner hundreds of miles with my manual trans Subaru Forester in overdrive without trouble. I keep Mobil 1 gear oil in it and change it every 20k, however. (I don't use the Forester any more for towing the boat since it admittingly was overloaded and I now have a much more capable vehicle)

The reason for automatics, from my knowledge, was to keep the unit from changing between overdrive (or its highest gear) and 3rd (or the next gear down). This shifting generates more heat plus the wear of shifting under load.

Some vehicles don't have this issue though. I was driving my buddy's '99 3/4 ton GMC with a 454 and 4.10 rear towing a 2 axle U-Haul with a fwd Mercury Capri through the mountains out east and it NEVER had to downshift

Modern units can automatically lock out the highest gear if a load if it detects a large load. Locking out overdrive has been replaced by tow/haul modes too...like my mom's Hemi Durango with it's 5 speed auto and tow/haul doesn't quite lock out overdrive...seems to slip the torque converter a little bit instead.

If you have a vehicle with a 3 speed auto like me you don't have to worry

 

[Pontuned]

Re: Why is towing in overdrive bad?

I have been the GM for a transmission repair center for nearly 10 years so I have a pretty firm grasp of how each transmission performs. Dodge gets a bad rap for their 48RE but it actually has a much stronger overdrive than the 4R100 or the 5R110. The Allison 1000 is the best of the 3 choices (contrary to what someone may think), it is an very strong unit.

The pumps on the 4L60E hasn't really undergone a significant change since 1994 when they went to the PWM design. The design of the input drum on these units are the main reason for towing failures in OD (weak 3-4 clutch section and lower apply pressure) and it is more prone to failure in the later design with the larger diameter shaft (cracking around shaft).

All that said, I own a Dodge 2500 Cummins HD with the 48RE. I like the simple design of the unit and the lower expense of repair (parts cost vs Ford or Chevy) in the event of a failure. I am a big fan of the Cummins engine so the combo is a win/win for me.

Each of the offerings of the big three have their strong and weak points and none of them are immune to failure. I have repaired more 4L60E's, 4L80E's, 46/47/48RE's and E4OD/4R100's than I can count. I can count the # of Allisons on one hand.

 

[foodfisher]

Re: Why is towing in overdrive bad?

$3,000 transmission replacement and three day's waiting for a replacement in a foreign city, Yuma. One good thing about Yuma, Bought a bicycle at a 2nd hand store and could tour the whole town without too much effort.

 

[Pontuned]

Re: Why is towing in overdrive bad?

$3,000 transmission replacement and three day's waiting for a replacement in a foreign city, Yuma. One good thing about Yuma, Bought a bicycle at a 2nd hand store and could tour the whole town without too much effort.

What type vehicle are you having repaired?

 

[22E6441]

Re: Why is towing in overdrive bad?

I've got a 2006 GMC Envoy 4.2L 4x4.

My boat is pretty small.....maybe 2500 pounds fully loaded with gear. I don't know, that may be way to high.....not really sure though....I should probably get it weighed to see. It's light enough that I load it crooked on the trailer I can basically shoulder check it into place. Two guys can lift and scoot it a few inches easy as well.

Considering that my boat is about half my max towing capacity, I should be fine in OD right?

 

[JaseBosto]

Re: Why is towing in overdrive bad?

I've got a 2006 GMC Envoy 4.2L 4x4.

My boat is pretty small.....maybe 2500 pounds fully loaded with gear. I don't know, that may be way to high.....not really sure though....I should probably get it weighed to see. It's light enough that I load it crooked on the trailer I can basically shoulder check it into place. Two guys can lift and scoot it a few inches easy as well.

Considering that my boat is about half my max towing capacity, I should be fine in OD right?

My stingray weighs in at 2100 lbs bone dry and there is NO way your gonna should check that into place....unless you weigh 500 lbs that is....2 guys could not pick it up either. I bet 3 couldnt even do it.

 

[smokeonthewater]

Re: Why is towing in overdrive bad?

My stingray weighs in at 2100 lbs bone dry and there is NO way your gonna should check that into place....unless you weigh 500 lbs that is....2 guys could not pick it up either. I bet 3 couldnt even do it.

You might be surprised.... shoving a 2500 lb boat and bouncing it into place isn't that tough.... Now YOU might not be able to do it but that doesn't mean he couldn't...

 

[swey00]

Re: Why is towing in overdrive bad?

SuperNova,

I have a 1999 1/2T Silverado. Were the low fluid flow issues fixed by then? The 1999 model came out really early because that is when they changed body styles. My rule of thumb has always been put it in the gear that kept it from hunting between gears but had never heard of the temperature problem due to low fluid flow.

I really liked my 3/4T Suburban with its tranny gauge in the dash. Does the 1/2T tranny have similar provisions already there that allow you to read temp? Do you know if the tranny temps can be read over OBD2 on the 1/2Ts?

I have a 2002 silverado 1500(1/2t) excb. From what I have read on a couple of other forums, when hooked up to a computer you can get the reading for the trans temp on all new body 99+ silverados and sierras. If yours is a 99, I would look for a 99 2500 cluster. There is not to much information on it, but a couple people think there might have been a slight redesign on the 00+ gauges.

I just purchased a seirra 2500(3/4t) gauge cluster from a 6.0 w/trans temp gauge. It should be here by wednesday, so I should have it installed by friday, weather permitting.

 

[northernmerc]

Re: Why is towing in overdrive bad?

A few people have stated that towing in high gear is OK with a standard transmission. I have a bill for more than a thousand dollars that proves otherwise.

This was on a Toyota pickup with a 5 speed transmission. I bought the truck new, so know its history. After towing a SeaRay 180 for a few years, high gear developed a loud howl. A bearing went out at just over 100,000 km (62,000 miles). The transmission shop that rebuilt it said that was caused by towing in high gear. The explanation they gave was that towing in 5th puts a lot more strain on the transmission than towing in 4th because 4th utilizes a more direct, straight through pattern.

The transmission shop also compared the Toyota transmission to a sewing machine, meaning the gears and other parts are quite small. I guess they had worked on lots of them.

After that, I remembered to tow in 4th with any standard Toyota. A little extra gas costs a lot less than rebuilding a transmission.

After 25 years of driving Toyota pickups, I finally got fed up with various other problems. So far I love my GMC 3/4 ton. I'm glad that they put transmission temp gauges on them and that tow/haul mode.

 

[q5ka]

Re: Why is towing in overdrive bad?

My 06 Dodge Cummins has an OD off and a tow mode. I use tow mode when well towing. It adjusts the shift points along with torq convert lockup rpms. It still allows OD to activate but requires higher speed to shift. On same note, the only time I have ever ran with OD off, force activate the engine brake. As it has been said time before, read your manual along with learn how to feel the truck/car. I have put a full set of gauges (grew up in an over the road trucking family) in so I know what the truck is doing and know how to feel the truck out. If you have a truck/car that is setup to tow the weight you are hoping to pull, then all should be good. If you are afraid that your auto is not able to handle the load in the way you want to travel, get a bigger/better rig or time for some upgrades

 

[SuperNova]

Re: Why is towing in overdrive bad?

I have a 2003 Silverado with the 4L60E and towing. Did they fix the pump issue by then? If I tow through hilly terrain I usually put it in (D). A V8 might not need to do that but my 6 does. On flats and slight inclines it won't shift out.

They had it fixed by '98

 

[SuperNova]

Re: Why is towing in overdrive bad?

I know when I worked at a Dodge dealer, the techs there told me to put my trans in neutral for a minute or so when I started it, don't recall exactly why. I know with the stock trans if I threw it right into drive, it would sometimes slip. If I let it sit in neutral for no more than a minute, it never slipped.
Not sure on the why, I took apart a TH350 once years ago, and almost went nuts trying to figure it out hahaha

The trans didn't slip...the torques converter just wasn't transferring energy efficiently because some of the fluid had drained out of it....you threw it into neutral because that was where the torque converter fill circuit was...as soon as the torque converter was full, you were good to go.

 

[skargo]

Re: Why is towing in overdrive bad?

The trans didn't slip...the torques converter just wasn't transferring energy efficiently because some of the fluid had drained out of it....you threw it into neutral because that was where the torque converter fill circuit was...as soon as the torque converter was full, you were good to go.

Thanks Stan, I had no idea, I just knew it worked.