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Open Roads Forum  >  Travel Trailers  >  General Q&A

 > Towing up grades with "M" and 1 gears

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crasster

Dallas

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Posted: 04/03/21 12:26pm Link  |  Quote  |  Print  |  Notify Moderator

So I have several coaches, but this will be my first attempt pulling a TT up a steeper mountain grade.

I'm towing with a 1 ton Chevy express 3500. I'm a bit "confused" on just how to use this transmission.

P-R-N-D-M-1 are the gears.

So I know what gear 1 is. But the big question is around the M gear.

I've been told to go to M 3 for towing up / down grades. But I'd like a bit more input than just one random stranger. So I came here to have input from several random strangers. [emoticon]

I have 2 examples and would like to know what YOU would do if you were driving with my gearset.

1) Driving along, minding your own business, tow button depressed on the dash. Brake controller all good. Suddenly you see one of those yellow signs with a truck going downhill. 7% grade for the next 4 miles. What do you do with speed/gears/etc.?

2) At the bottom of the long hill, you realize you left your wallet at the gas station 10 miles back. Now you turn around and have to drive up 7% for 4 miles. What do you do with speed/gears/etc.?


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toedtoes

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Posted: 04/03/21 12:51pm Link  |  Quote  |  Print  |  Notify Moderator

Basically, the M is manual mode. It allows you to manually shift through the gears by pushing the + or - buttons. The number next to the M is the gear you are currently in.

With that, I would say use M when in mountainous regions and shift gears like you would with a manual transmission to keep the auto transmission from switching gears constantly.


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Gdetrailer

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Posted: 04/03/21 01:23pm Link  |  Quote  |  Print  |  Notify Moderator

"M" for "manual mode"..

M mode is for those guys that want their "handshaker" back.

Just put it into to drive and enable the "towing/haul" mode and forget about that "M" mode.

I would recommend reading your specific owners manual first.

The general idea of the Tow/haul mode is the drive train will adjust the shift pattern strategy which tends to be very helpful while towing or hauling loads. This mode (at least on Fords) will also engage auto downshifting when descending hill or steep downgrades.

The auto downshift is a very handy feature, as you start down a hill, when you let off the gas pedal it should start downshifting to lower gear to maintain your speed without the need to stand on your brakes all the time. If you continue to gain speed, the transmission should automatically downshift to the next lower gear automatically.

This is the same idea as manually selecting a lower gear on older vehicles without Tow/haul but you do not typically need to do that with tow haul most of the time.

You should also be able to tap or lightly touch your brake pedal to override the current gear and drop to the next lowest gear if you feel you are needing to slow down further or not gain more speed (at least that is how Ford does theirs).

Tow/haul should also slow the upshifting some, holding gear upshifts out until engine is in the proper RPM for the load, this helps reduce constant upshift/downshift known as "gear hunting".

As far as your #1, Follow posted speed recommendations and do nothing, allow Tow/haul to manage your gear selection, that is what it was designed for. As you start down the hill, let off the gas and transmission should start downshifting for you. If you feel you are gaining too much speed, tap or touch the brakes lightly to downshift to the next lower gear. You can always add some brakes as needed if you feel too uncomfortable with the speed you are descending at.

Your #2 put it into Drive enable tow/haul and allow the drive train figure out what gear to use.. But if starting out from a dead stop on a steep grade, don't expect to win any races off the launch pad and you will be fine..

Towing really zaps how fast off the line you can go, you don't need to try to win any Nascar races and you aren't going to either.

Take your time, it isn't all that hard towing but it does take time to get used to the different feel.

I would suggest taking the rig out for a couple of test runs on some light grade hills before trying long steep grades if you can. This way you will get a feel for what the vehicle will do..

* This post was edited 04/03/21 01:31pm by Gdetrailer *

Grit dog

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Posted: 04/03/21 01:56pm Link  |  Quote  |  Print  |  Notify Moderator

While real world doesn’t always work out like the previous poster let’s on, manual mode IS very handy to keep the trans from up or downshifting unless you want it to.
Higher rpms = more power uphill and more compression braking downhill.
So heading down the hill, to minimize brake use, keep the rpms up in the 3-4k range and you find lock the highest gear it will shift into for the speed you are maintaining down thehill.
After you realize your wallet is gone, and you turn around, you’ll likely choose the same top gear for heading back up the hill. Whatever the speed you are pulling, choose the top gear that keeps the engine in its power band.


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time2roll

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Posted: 04/03/21 02:04pm Link  |  Quote  |  Print  |  Notify Moderator

Just use D unless there is excessive shifting. RTFM for the M (manual) mode.


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afidel

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Posted: 04/03/21 02:14pm Link  |  Quote  |  Print  |  Notify Moderator

On my GM transmission tow/haul auto works great. Please note that to get engine braking to work I have to manually brake below 50mph, the transmission and engine won't go into lockup and engine compression braking until I hit ~48mph if going faster than that.


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Gdetrailer

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Posted: 04/03/21 02:19pm Link  |  Quote  |  Print  |  Notify Moderator

afidel wrote:

On my GM transmission tow/haul auto works great. Please note that to get engine braking to work I have to manually brake below 50mph, the transmission and engine won't go into lockup and engine compression braking until I hit ~48mph if going faster than that.


Well that is a bit less than useful.

Never noticed that on any of my Fords starting with the 2006, 2013, 2019 and now my 2020. Auto downshift on mine don't seem to have any required speeds to activate, just does it which is very handy on a hill I must go down into town which is 11% grade and speed at the top of the hill is 35 MPH..

crasster

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Posted: 04/03/21 03:27pm Link  |  Quote  |  Print  |  Notify Moderator

Okay great responses thus far. Sounds like tow/haul really makes things easier than decades back. [emoticon]

Gdetrailer

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Posted: 04/03/21 03:55pm Link  |  Quote  |  Print  |  Notify Moderator

You bet, T/H is a very nice advance in vehicles, makes towing much less of a "on the edge" thing having to worry about what gear to be in.

Read the owners manual concerning your T/H feature on your vehicle as afidel has mentioned about a possible speed engagement limitation or any other T/H features on GM..

I am kind of spoiled by my Fords which doesn't seem to have a minimum speed for T/H to downshift engage, mine always seems to work at any low speed. Also mine automatically will upshift once I get to the bottom of a grade and I start adding gas pedal at pretty much any speed.

1ed

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Posted: 04/03/21 04:16pm Link  |  Quote  |  Print  |  Notify Moderator

I just use cruise control and set it for about 45 going down .

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