6 speed transmission questions.

[Bank_of_Dad]

So I came out of the ice age and got a Suburban with the new 6 speed transmission (PRNDM_1). Reading the manual, it seems a little daunting.

So how do you use it when towing? And what about steep downhill grades (short or long) when towing. I'm used to just downshifting into 2nd.

Thanks

Judy

[travisd1000]

GM Says you don't even need T/H until you're > 75% of the tow capacity, but there's no harm in using it whenever -- just possibly reduced gas mileage. I tow ~6k on my 1/2 ton Silverado 1500 -- I use T/H when it's hilly, or when in town. Out on the highway and up to speed I usually drop it out and let it shift into 6th when it wants to. Use M and select a gear if it's hunting.

You probably have a transmission temp gauge via the DIC - use it. If you're climbing over 200, you're getting into the problem zone. I can switch into T/H and watch the temp drop.

[The_Texan]

ktosv wrote:


Also, if you select 2, it will start in 2nd gear and stay in 2nd gear. Awesome for a 2wd vehicle like mine in deep sand or snow.

Nope, select 2 and it will start in 1 and shift to 2. It is NOT a manual transmission, just a top gear selector.

[Bank_of_Dad]

Right. Its 4wd 3/4 ton.

[Hybridhunter]

GM's don't have true manual shifting, it's a "range select" only. It only limits up-shifting, it does not allow manual control, and does not manually upshift when used, it just limits up-shifting of the selected gear. Just an FYI, it's manual in name only. It merely replaces the multiple positions previously available on a column shift.
But the Tow/Haul calibrations are pretty good when just left alone. I used to regularly lock out sixth on my 1 ton to limit hunting.

[TomG2]

You can simply select tow/haul mode and put it in Drive, but a lot of us like to take advantage of the manual shifting option. Coming up to a big hill? Tap it down a gear. Rolling down the other side? Upshift to save a little gas. It's all good and the six speed makes choosing the right gear easy.

[ktosv]

Do you have a 1/2 ton or 3/4 ton? If 3/4 ton, I am thinking you might be able to just drop it into Drive and be good with that size trailer. When approaching a steep downgrade and you think you will need to shift down, just drop it to M. It may automatically drop to the next lower gear than you are in (if cruising in 6th, it might drop to 5th when you go to M). Just shift up and down as needed when needed.

If you have the 1/2 ton with the 3.42, you may have to use M all the time and limit the truck to 5th gear.

The next time you are out with just the truck, drop it into M and shift down a couple of gears to experiment what it does. I don't think you will hurt anything as if you select too low of a gear for the current speed, it should hold the previous gear until it can downshift. Of course, someone behind you might not appreciate you slowing down this way.

Also, if you select 2, it will start in 2nd gear and stay in 2nd gear. Awesome for a 2wd vehicle like mine in deep sand or snow.

[ksss]

I use manual a lot in my Duramax when towing heavy. It runs cooler when I do the shifting.

In my 2500HD with the 6.0 I have yet to use the manual function when towing heavy. I use tow/haul and plant the right foot to the carpet.

[Bank_of_Dad]

Thank you Texan, T/H on the end of column.

Downtheroad, its much more interesting getting comments here than reading the manual:)

[Turtle_n_Peeps]

Put it in D, press the tow/haul button and drive.

[downtheroad]

6 speed..GM automatic - does it have a button on the shift arm or on the column for Tow/Haul?

If so, just use 'D' and Tow/Haul when towing.
Did your Burb come with a manual in the glove box?

[Bank_of_Dad]

I tow TT or Horse Trailer about 6000. TT has Equilizer brand sway bars on it.

[The_Texan]

Excellent transmission. 99% of the time when towing, select D and T/H mode then let the tranny do the work deciding what and when. It has a built in transmission brake when T/H is selected and mine will hold us(10K trailer) at 60 MPH on a 7% downgrade for over 5 miles. When climbing a grade, if you are not satisfied with the speed, select M and then what ever gear you feel will do the job at a reasonable RPM. this transmission is so much better than the 4 speed it isn't even a close comparison.

[TomG2]

Depending on the load, you may want to (M)anually select 4th or 5th for the top gear you will be using. Set the tow/haul mode and you are ready to go. It will downshift going downhill as needed.