Overdrive or not?

[shasta24]

I finally purchased my first three quarter ton suburban with 8.1 motor. Until now I had a half ton with 350. I always towed in third gear because I understood that towing in overdrive was a no no. Now with this huge motor and trans. does this rule still apply? It has 4.10 gears with the tow haul mode button. Should I use that button when towing and pull shifter down to 3rd? Thanks for your help. Also my trailer is a 79 Shasta that dry weight is 5250 pounds.

[jasoncw]

In my Excursion (4-speed), I leave it in D. Most of my towing is on the flat lands here in MI, so it generally does not shift in and out of OD. Plus, I definitely get better fuel mileage at 65 in D than in tow/haul (3rd gear). And actually, for the Excursions (gasser transmissions), it is not tow/haul mode, but rather "OD Off".

[kaydeejay]

Tvov wrote:
Feel free to tow with headlights on... I was just wondering if it was yet another law passed that I didn't know about.

Not a law in the US. Canada requires daytime running lights (DRLs) on all vehicles since around 1994. Started in Sweden when they documented a 30% reduction in daytime accidents if vehicles had headlights on.
I believe all GM vehicles (and some others) have incorporated DRLs into US sold vehicles as well.
It does improve other driver's awareness of your vehicle.

[DustyR]

3oaks wrote:

majorgator wrote:

Jack_Diane_Freedom wrote:
Just engage the tow haul button and go the computer will select the right gear.

This is not entirely accurate. While the Tow/Haul button will change shift points and thus prevent you from advancing gears at the lower RPM's, it will not keep you out of overdrive during heavy tow modes. The best and really only useful way to determine if OD is OK is to drive and experience it yourself. If it's shifting in/out of OD frequently, then don't run there. Keep an eye on trans temps and monitor the shifting.

No one here said the Tow/Haul mode would keep a vehicle out of overdrive. But the tow/haul mode will automatically select the right gears and keep the transmission from continually hunting through the gears including overdrive.

When towing, I like others select the Tow/haul mode. Set it and forget it. That's what it's there for. Takes the guess work out of which gear to manually select or lock the transmission out of.

I have a HD2500 Chevrolet Duramax and utilize the tow/haul mode when ever the unit is loaded or towing. The t/h mode raises the shift points and reduces transmission heat. The vehicle doesn't shift in to overdrive until apx 62 MPH. The t/h mode also utilizes the engine brake and towing in manual mode also let me control/limit the shifting of the transmission. Let the computer do its job, if it searches during those occasional steep inclines restrict the transmission with the paddle switch on the shifting lever.

[Tvov]

Feel free to tow with headlights on... I was just wondering if it was yet another law passed that I didn't know about.

[owenssailor]

spoon059 wrote:

Tvov wrote:

owenssailor wrote:
....

(I also always turn on the headlights when towing)

Is that something we're supposed to do while towing? I don't think I've heard of that before.

Don't think you are "supposed" to, but I ALWAYS drive with my headlights on. You are much easier to see with your lights on, even during the day. If it helps prevent someone from pulling out in front of you, it was worth it!

Many years ago Greyhound bus did a study about headlights on during daylight. They had part of the fleet always have the headlights on. The result was fewer occasions where the bus was cut off by other drivers. I figured that if it made a difference to noticing a bus it should help noticing other vehicles. I drive with headlights on most of the time and always when towing.

[BurbMan]

krobbe wrote:
The GCWR for your truck is 19000lbs. The curb weight is 5800.

No....If its an LT and loaded with options like mine the "curb weight" is more like 6700 lbs.

At any rate plenty of capacity for that Shasta. Use tow/haul, tow in OD all day long, watch the trans temp gauge, it should never go above 200*.

[Turtle_n_Peeps]

Your Burb has a 4L85E in it for a tranny.

Yes you can tow with your Burb in OD and it won't hurt anything. Tough tranny.

[Mr_Beebo]

Turning your headlights on during the day will activate the running lights on your camper and just make you that much more visible. Can't hurt.
Seems the biggest reason folks ask if they need to use the tow/haul mode is regarding gas mileage. There is a perception that keeping your transmission in overdrive or high gear when towing may save you a little gas. My experience is that is does not. There has been lots of discussions regarding the old throttle control by wire setup vs the computer controlled throttles today. Whatever difference there may be, if any, with my truck running 60 mph in OD @ 1800 rpm vs 2250 rpm in tow/haul mode when towing won't offset the cost of another transmission.

[spoon059]

Tvov wrote:

owenssailor wrote:
....

(I also always turn on the headlights when towing)

Is that something we're supposed to do while towing? I don't think I've heard of that before.

Don't think you are "supposed" to, but I ALWAYS drive with my headlights on. You are much easier to see with your lights on, even during the day. If it helps prevent someone from pulling out in front of you, it was worth it!

[Tvov]

owenssailor wrote:
....

(I also always turn on the headlights when towing)

Is that something we're supposed to do while towing? I don't think I've heard of that before.

[krobbe]

The GCWR for your truck is 19000lbs. The curb weight is 5800. Add 600 for passengers and gear, 6400lbs. Add 6300lbs for your TT and you're at 12700lbs.
That is 67% of the 19000 GCWR. Close enough, use Tow/Haul mode.

[owenssailor]

With my 2012 Chev 1500 I always use towhaul when towing the trailer. It rarely goes into 6th but that is fine. This has worked well towing for the last 3 years with a 6500 lb trailer. It is also what the manual says to do.

(I also always turn on the headlights when towing)

[krobbe]

Section 4-51 of your manual says to tow in D unless it shifts too often while towing heavy loads or on hilly roads.
The next page states that the tow/haul mode reduces the frequency and improves the predictability of shifts. Best to use when the vehicle and trailer combined weight is 75% or more of the GCWR.

[Dadoffourgirls]

I towed my trailers in D when I had my Yukon XL with 8.1. In Michigan, I never had a problem with it continuously between 3rd and 4th.