2017 GMC 6.0 Vortec - Manual Shifting?

[Mbranscum]

I notice when I am towing my RV, my truck seems to try and down shift sometimes when climbing a hill before it should. Do any of you guys manually shift to get more power or save gas in these situaltions?

Or do you just let the computer control it and go with the flow?

I believed I have a 4.10 rear end with a 6.0L Gas engine.

Thanks.

Mike

[kw_00]

mkirsch wrote:
I've tried to use Manual mode to manually shift up through the gears... and it doesn't work well. It's not like the "flappy paddle" shifters on performance cars. The reaction is severely delayed.

Yes very true, was never designed for that application. The advantage in using it is primary locking out gears that you can't or don't want to use while towing, and of course quick downshift. It works much better in my opinion then letting the computer shift for u on tough grades. Seems like GM will let the engine almost bog down before the up shift sometimes. Watch the TFL test u will see what I mean. So they gave us that easy quick way of keeping the truck in its powerband. Like I said before, I will drop a gear prior a hill sometimes just to keep speed. It only jumps up a few rpm but keeps it in the power band when I most need it. Won't harm a thing, no different then downshifting a manual tranny.

[Rubiranch]

Hybridhunter wrote:
ford manual mode, and it just shifts when you tell it too, up or down.

I sure wish my Chevy was like that. I think they all should seeing that we can't buy a truck with a manual trans anymore.

I could pull more hills in a higher gear if I could control the shifts.

[Hybridhunter]

mkirsch wrote:
I've tried to use Manual mode to manually shift up through the gears... and it doesn't work well. It's not like the "flappy paddle" shifters on performance cars. The reaction is severely delayed.

That's because it doesn't shift up, as mentioned it's a range select only.
I can only speak to the effectiveness of the ford manual mode, and it just shifts when you tell it too, up or down. I often just lock in 5th, set the cruise, and enjoy the relaxed ride.

[Rubiranch]

pcaffrey wrote:
Let the computer do its job.

I don't think the manufactures are as dumb as some people like to think they are.

[pcaffrey]

We own a 2016 Chevy 2500 HD, 6.0/6sp. Tow 12,000 5TH. with trans in tow haul mode and M5. Let the computer do its job. Trans is also equipped with a grade breaking mode and it does work well, had no issues thru the Smokies this past June. Check your owners manual for instructions to insure it is engaged. Happy travel's

[mkirsch]

I've tried to use Manual mode to manually shift up through the gears... and it doesn't work well. It's not like the "flappy paddle" shifters on performance cars. The reaction is severely delayed.

[KD4UPL]

Man this post got off track fast. I don't remember a question about transmission slipping.
OP, what do you mean "before it should"? I would think the computer in your truck knows far more about when to shift than you or I do.
Ignore all the posts about lugging; downshifting will in no way cause the engine to lug, quite the opposite.
Modern truck engines like you have are meant to turn a lot more RPMs than older models. I often see 5,000 RPM or more on my 2015 Chevy 6.0. Just today I was towing 14,000 pounds and it was over 5,000 accelerating up a hill. This is normal, expected, and the proper way for the truck to behave. As for saving fuel, I would be far more concerned about having the engine in it's proper power band, the transmission locked in and running cool, and maintaining proper road speed before fuel mileage even crossed my mind.
I find the transmission does a pretty good job of knowing what gear to be in. I will generally use the manual mode only to downshift when descending a grade to keep speed in check.

[kw_00]

Whats really nice also about using the M feature is that you can lock out gears. So if u toggle up to 5 then the computer locks out 6th gear. I really use this feature when towing. I love to have more control when running the hills either up or going down. Also if I'm going through heavy or slow city traffic while pulling the camper then I can leave it in 4th gear and lock out 5 and 6th. I got back from Trip to Georgia last month, I took hwy 19 on the way up while following my parents. We kept the speed at 65mph this time and I even locked out 5th and 6th when I got to some of the hilly areas. Kept my speed with out any issues. BTW I pull around 10k and have no issues.

[transamz9]

drsteve wrote:

transamz9 wrote:

SidecarFlip wrote:

transamz9 wrote:

SidecarFlip wrote:
Always keep in mind that when an automatic trans up shifts or down shifts, thats is when the box makes the most heat.

It makes heat through hydraulic actuation and it makes heat as the clutch packs engage under heavy load and gear ratio selections are programmed to feel smooth. It's the smooth feel that makes the heat (and wear) because the clutch pack hydraulic pressure is modulated for smoothness. That slipping makes the heat.

While I don't have a GM, I manually downshift out of OD into direct prior to ascending a hill when the motor isn't producing a gob of power (Torque) and the clutch packs can engage with less residual heat. I run a shift kit as well and my shift kit increases the hydraulic pressure and how fast it rises, thereby clamping the packs quicker.... less heat

I might be wrong but you don't ever want your clutch packs to slip. You want your torque converter to do the slipping. That's what it's for.

Your clutch packs always slip to some degree as the internal ratio's change. They aren't an on-off switch. If they were, you'd rip your universals out or twist the drive shaft. The more they slip, the more heat produced and conversely, the smoother the shift is. How an automatic transmission works.

When my TC locks there is no slippage.;)

When the TC locks here is no torque converter slippage, but when the transmission shifts, the clutch packs DO slip as it moves from one gear to the next.

I toasted the 700R4 in my 92 GMC conversion van by towing overweight, and when I had it rebuilt, I told the shop--a performance oriented place--what I was doing, and what I wanted, which was lower temps and a trans that would last. The difference when they got done was like night and day. The improved trans shifted like it meant it, the shift points were higher when I got on it, and the temps were nice and low.

But yeah, Sidecarflip is correct, the clutches do slip, by design. Those buttery soft shifts are nice, just not for towing.

I guess your definition of slip is different from mine. When I think of slippage I'm thinking of overpowering the clutch. If you are slipping the clutch packs to the point of heating the transmission then you have transmission issues. An unlocked TC is usually the main reason a transmission gets hot.

My 2005 Ram has the so called weak 48 that still pulls and shifts like it did when I brought home new. I have been putting way over stock power through it since it was 5years old and towing WAY over it's capacity. The trick is that the TH button was always on anytime it had a trailer hooked to it. When playing with the added power the TH button is on. When pulling heavy it was always manually shifted to 2nd gear because when done that way it will lock the TC in 2nd with TH on.

[Rubiranch]

Mbranscum wrote:
OK..so when should the +/- manual shift switch for on the shifter be used?

Mines a 2011 6.0L like your's.

I leave mine in drive with the tow haul mode selected when I have my camper loaded in the truck and let the truck decide when to sift. It will up-shift later when accelerating and down shift sooner when climbing hills that it will when the tow haul mode is not selected.

Selecting the +- seems to only do any good for down shifting when decelerating.

If you select 5th gear in the manual shift mode and the trucks wants 4th gear it will shift into 4th regardless of what you select.

[Hybridhunter]

APT wrote:
Manual mode for GM is more like top gear range limit. You cannot force the trans to hold a taller gear than computer wants. If you don't want it to downshift, let off the accel pedal.

Sorry, say this after my post.

[Hybridhunter]

kw/00 wrote:
You can use the toggle switch to change gears when it's in the M mode. I drop the gear manually on mine prior any large hill.

Only to downshift....it is a range select only on the GM's, not a true manual, like some other brands.

[drsteve]

transamz9 wrote:

SidecarFlip wrote:

transamz9 wrote:

SidecarFlip wrote:
Always keep in mind that when an automatic trans up shifts or down shifts, thats is when the box makes the most heat.

It makes heat through hydraulic actuation and it makes heat as the clutch packs engage under heavy load and gear ratio selections are programmed to feel smooth. It's the smooth feel that makes the heat (and wear) because the clutch pack hydraulic pressure is modulated for smoothness. That slipping makes the heat.

While I don't have a GM, I manually downshift out of OD into direct prior to ascending a hill when the motor isn't producing a gob of power (Torque) and the clutch packs can engage with less residual heat. I run a shift kit as well and my shift kit increases the hydraulic pressure and how fast it rises, thereby clamping the packs quicker.... less heat

I might be wrong but you don't ever want your clutch packs to slip. You want your torque converter to do the slipping. That's what it's for.

Your clutch packs always slip to some degree as the internal ratio's change. They aren't an on-off switch. If they were, you'd rip your universals out or twist the drive shaft. The more they slip, the more heat produced and conversely, the smoother the shift is. How an automatic transmission works.

When my TC locks there is no slippage.;)

When the TC locks here is no torque converter slippage, but when the transmission shifts, the clutch packs DO slip as it moves from one gear to the next.

I toasted the 700R4 in my 92 GMC conversion van by towing overweight, and when I had it rebuilt, I told the shop--a performance oriented place--what I was doing, and what I wanted, which was lower temps and a trans that would last. The difference when they got done was like night and day. The improved trans shifted like it meant it, the shift points were higher when I got on it, and the temps were nice and low.

But yeah, Sidecarflip is correct, the clutches do slip, by design. Those buttery soft shifts are nice, just not for towing.

[transamz9]

SidecarFlip wrote:

transamz9 wrote:

SidecarFlip wrote:
Always keep in mind that when an automatic trans up shifts or down shifts, thats is when the box makes the most heat.

It makes heat through hydraulic actuation and it makes heat as the clutch packs engage under heavy load and gear ratio selections are programmed to feel smooth. It's the smooth feel that makes the heat (and wear) because the clutch pack hydraulic pressure is modulated for smoothness. That slipping makes the heat.

While I don't have a GM, I manually downshift out of OD into direct prior to ascending a hill when the motor isn't producing a gob of power (Torque) and the clutch packs can engage with less residual heat. I run a shift kit as well and my shift kit increases the hydraulic pressure and how fast it rises, thereby clamping the packs quicker.... less heat

I might be wrong but you don't ever want your clutch packs to slip. You want your torque converter to do the slipping. That's what it's for.

Your clutch packs always slip to some degree as the internal ratio's change. They aren't an on-off switch. If they were, you'd rip your universals out or twist the drive shaft. The more they slip, the more heat produced and conversely, the smoother the shift is. How an automatic transmission works.

When my TC locks there is no slippage.;)