Power Drive

Already done so for both list :)
The support network I've seen while researching the GMCs as well as the knowledge sharing among the owners was one of the factors that lessened my
anxiety over purchasing a 40+ year old coach.

> Vadim
>
> When you get a chance, could you connect with John Shotwell and record your
> TZE number so we know where these machines are living :)
> And there is also the Black List for you to get on...help for the GMC owner
> when on the road. If you need more info on finding these, let us know.
> Thanks for the sig addition to your posting....
>
> Mike in NM
>
> On Mon, Dec 18, 2017 at 1:14 AM, Kingsley Coach

>
> > Ken
> >
> > I've followed Kerry Tandy through El Paso in the outside lane at 4:30
> > doing 75 + ...Clearly a student of your driving school !
> >
> > Mike in Las Cruces
> >
> >
> > Virus-free.
> > www.avast.com
> >
> >
> >
> > On Mon, Dec 18, 2017 at 12:24 AM, Richard Denney

> >
> >> Only the Redhead, when punching a hole through Atlanta traffic at 70 mph
> >> on
> >> a congested freeway, but I actually think it was Manny the Maniac that was
> >> driving your coach.
> >>
> >> Rick "who needed that big margarita after that one" Denney
> >>
> >> On Sun, Dec 17, 2017 at 9:57 PM Ken Henderson

> >>
> >>> Or, if you HAVE to get on a freeway, and it makes you more comfortable,
> >>> stay with the traffic. The GMC should still be comfortable at 75-80.
> >> :-}
> >>>
> >>> ​Just what I do -- but, then, there are some who advise against
> >> caravaning
> >>> with me. :-{​
> >>>
> >>> Ken H.
> >>
> >> --
> >> Rick Denney
> >> 73 x-Glacier 230 "Jaws"
> >> Off-list email to rick at rickdenney dot com
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >>
> >
> >
> >
> > --
> > Michael Beaton
> > 1977 Kingsley 26-11
> > 1977 Eleganza II 26-3
> > Antigonish, NS
> >
> > Life is too short to hold a grudge; slash some tires and call it even !
> >
> >
> >
>
>
> --
> Michael Beaton
> 1977 Kingsley 26-11
> 1977 Eleganza II 26-3
> Antigonish, NS
>
> Life is too short to hold a grudge; slash some tires and call it even !
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
You're on top of things, young fellow !
Thanks

Mike in NM

On Mon, Dec 18, 2017 at 2:01 PM, Vadim Jitkov
wrote:

> Already done so for both list :)
> The support network I've seen while researching the GMCs as well as the
> knowledge sharing among the owners was one of the factors that lessened my
> anxiety over purchasing a 40+ year old coach.
>

> > Vadim
> >
> > When you get a chance, could you connect with John Shotwell and record
> your
> > TZE number so we know where these machines are living :)
> > And there is also the Black List for you to get on...help for the GMC
> owner
> > when on the road. If you need more info on finding these, let us know.
> > Thanks for the sig addition to your posting....
> >
> > Mike in NM
> >
> > On Mon, Dec 18, 2017 at 1:14 AM, Kingsley Coach

> >
> > > Ken
> > >
> > > I've followed Kerry Tandy through El Paso in the outside lane at 4:30
> > > doing 75 + ...Clearly a student of your driving school !
> > >
> > > Mike in Las Cruces
> > >
> > >
> > > Virus-free.
> > > www.avast.com
> > >
> > >
> > >
> > > On Mon, Dec 18, 2017 at 12:24 AM, Richard Denney

> > >
> > >> Only the Redhead, when punching a hole through Atlanta traffic at 70
> mph
> > >> on
> > >> a congested freeway, but I actually think it was Manny the Maniac
> that was
> > >> driving your coach.
> > >>
> > >> Rick "who needed that big margarita after that one" Denney
> > >>
> > >> On Sun, Dec 17, 2017 at 9:57 PM Ken Henderson

> > >>
> > >>> Or, if you HAVE to get on a freeway, and it makes you more
> comfortable,
> > >>> stay with the traffic. The GMC should still be comfortable at
> 75-80.
> > >> :-}
> > >>>
> > >>> ​Just what I do -- but, then, there are some who advise against
> > >> caravaning
> > >>> with me. :-{​
> > >>>
> > >>> Ken H.
> > >>
> > >> --
> > >> Rick Denney
> > >> 73 x-Glacier 230 "Jaws"
> > >> Off-list email to rick at rickdenney dot com
> > >> _______________________________________________
> > >> GMCnet mailing list
> > >> Unsubscribe or Change List Options:
> > >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >>
> > >
> > >
> > >
> > > --
> > > Michael Beaton
> > > 1977 Kingsley 26-11
> > > 1977 Eleganza II 26-3
> > > Antigonish, NS
> > >
> > > Life is too short to hold a grudge; slash some tires and call it even
> !
> > >
> > >
> > >
> >
> >
> > --
> > Michael Beaton
> > 1977 Kingsley 26-11
> > 1977 Eleganza II 26-3
> > Antigonish, NS
> >
> > Life is too short to hold a grudge; slash some tires and call it even !
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> --
> Vadim Jitkov
> '76 Glenbrook 26'
> Pullman, WA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

Life is too short to hold a grudge; slash some tires and call it even !
 
Vadim,

I have a 3.70 final drive in my '75 26 footer and I normally drive between 62 and 65 MPH with no problems. Most 3/4 ton pickups of the same era had
4.10 rear end gears and most 1-Ton pickups were equipped with 4.56 gears, with essentially the same size tires as our GMCs.

The main difference between then and now is the overdrive transmissions on the newer cars. Prior to that, trucks, motorhomes, etc ran at higher RPMs
than they do now. Of course, we were lucky to get much more than 100,000 miles out of those older vehicles, but that is only one of the reasons the
newer ones last longer.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
I'm really glad I posted this question here. All your replies and personal experiences have significantly calmed my anxiety about running the engine
at what I perceived were high RPMs. I've read some additional threads on the forum with people towing fairly heavy trailers with the same setup as I
have and traveling at highway speed limits without any issue for the engine and transmission. I feel much better now. Thank you all :)

Here is a follow up question (let me know if I need to start a new thread for this):
from the point of view of transmission, what is the best way to tackle hills on the road? In the area where I live, we have significant grades on
nearly all our roads. We've got multiple grades of 3-4% in any direction we get going and some very steep grades of 6-7%. I've read that its best to
slow down and downshift to "S" gear for tackling the grades. Should this be done on all climbs or just on those very hard 6-7% grades? What about
driving in town (again lots of hills, but driving at 25-35 MPH)?

> Vadim,
>
> I have a 3.70 final drive in my '75 26 footer and I normally drive between 62 and 65 MPH with no problems. Most 3/4 ton pickups of the same era
> had 4.10 rear end gears and most 1-Ton pickups were equipped with 4.56 gears, with essentially the same size tires as our GMCs.
>
> The main difference between then and now is the overdrive transmissions on the newer cars. Prior to that, trucks, motorhomes, etc ran at higher
> RPMs than they do now. Of course, we were lucky to get much more than 100,000 miles out of those older vehicles, but that is only one of the
> reasons the newer ones last longer.

--
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
Vadim,

I would suggest you download and review these two Operator Manuals for your 1976 GMC as they were written by the guys that built the
vehicle and it is reasonable to assume they knew how to operate them. :-)

Select the appropriate manual depending on the VIN number of your Glenbrook:

Up to TZE166V100877:

http://www.bdub.net/manuals/X7621A.zip

TZE166V100878 and later:

http://www.bdub.net/manuals/X7680B.zip

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Vadim Jitkov
Sent: Tuesday, December 19, 2017 3:24 PM
To: gmclist
Subject: Re: [GMCnet] Power Drive

I'm really glad I posted this question here. All your replies and personal experiences have significantly calmed my anxiety about
running the engine at what I perceived were high RPMs. I've read some additional threads on the forum with people towing fairly
heavy trailers with the same setup as I have and traveling at highway speed limits without any issue for the engine and
transmission. I feel much better now. Thank you all :)

Here is a follow up question (let me know if I need to start a new thread for this): from the point of view of transmission, what is
the best way to tackle hills on the road? In the area where I live, we have significant grades on nearly all our roads. We've got
multiple grades of 3-4% in any direction we get going and some very steep grades of 6-7%. I've read that its best to slow down and
downshift to "S" gear for tackling the grades. Should this be done on all climbs or just on those very hard 6-7% grades? What about
driving in town (again lots of hills, but driving at 25-35 MPH)?

Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
1. Don't use the automatic kickdown to choose a lower gear when climbing.
Shift down manually. This will maintain higher pressure on the clutches in
the transmission. Manny (the foremost TH425 expert) doesn't install
kickdown switches in his rebuilds.

2. Don't try to make real power at low RPMs, particularly below 2000.
Choose a lower gear. As Dick Paterson says to justify this recommendation,
the oil pump is only moving at half the speed of the engine.

3. Therefore, if the grade is so steep that you can't maintain RPMs in the
power band (2400 to 3600 RPMs, or thereabouts), slow down, manually
downshift, and keep the engine in the power band.

4. At low speeds and while accelerating, the transmission will do the right
thing.

5. From a stop, the stall slip of the torque converter will do what needs
to be done.

6. The GMC isn't a race car.

Rick "we have to be the drivetrain control computer" Denney

On Mon, Dec 18, 2017 at 11:25 PM Vadim Jitkov
wrote:

>
>
> Here is a follow up question (let me know if I need to start a new thread
> for this):
> from the point of view of transmission, what is the best way to tackle
> hills on the road? In the area where I live, we have significant grades on
> nearly all our roads. We've got multiple grades of 3-4% in any direction
> we get going and some very steep grades of 6-7%. I've read that its best to
> slow down and downshift to "S" gear for tackling the grades. Should this
> be done on all climbs or just on those very hard 6-7% grades? What about
> driving in town (again lots of hills, but driving at 25-35 MPH)?
>

> --
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
 
On steep grades. I shift manually to first, or sec. Run the engine RPM'=
s up to the point that I just keep moving.. Then what till I get to the top=
. And don't care how fast, or how long it takes. There is one point that ha=
sn't been covered. Your trans temps are lower with the 3:70, or 4:10 beca=
use there's less load on the trans. And the trans fluid pump is flowing mor=
e fluid to the trans cooler. As to engine life with higher RPM's back year=
s ago. Remember. Our engines back then used carburetors, and ran different =
clearances. PVC systems weren't as good. They were dirty engines back then.=
Engines will run longer with EFI systems installed. Bob Dunahugh 78 Roy=
ale Iowa Member GMCMI ________________________________ From: Bob =
Dunahugh Sent: Sunday, December 17, 2017 10:03 AM=
To: gmclist Subject: RE: Power Drive Vadim. Yo=
u covered the subject well. The T425 with a 3:07 FD, 14 inch tires, and a 4=
,000 lbs car was a good combination. GM had the peak HP for the 427, and 4=
55 reached in the 3,600 to 4,200 RPM range. So higher RPM's in the 4200 ran=
ge, and above isn't an issue. We have 16 inch tires, and 12,000 lbs as you =
covered. And a different cam profile. That's another can of worms. Till abo=
ut 2003 we only had the 3:07, and 3:21. I think there was a 3:42 from Cinna=
bar? So the Power Drive was a way to get the RPM's up to get out of luging=
our engines years ago. But as you mentioned. The PD is adding more load on=
the T425. Then Jim K at Applied GMC came out with some great FD ratio choi=
ces up to a 4:10 ratio. These ratios ended the luging. And allow the engine=
/trans to work more efficiently. Some say the PD,or a lower FD ratio are t=
he same. No. Not at all. Is the PD bad? No. It's better then nothing. In y=
our situation. I'd leave things as they are till you have trans issues. The=
n change the FD ratio. I'm thinking of going to 4:10 from my 3:70. Towing, =
or not. I'd recommend 3:70. When I'm pulling my enclosed trailer with a car=
in it. A 78 Royale 403, and the 3:70 FD. My GVW is about 21,000lbs. As a s=
ide note. My mileage went up with the 3:70. As to newer engines at 1500 R=
PM's at 65 MPH. Their design is another kind of animal. Bob Dunahugh Membe=
r GMCMI.
 
This makes perfect sense. Again it all comes down to engine RPMs on these big block engines. Just need to get comfortable at running it differently
than what I'm used to.

> 1. Don't use the automatic kickdown to choose a lower gear when climbing.
> Shift down manually. This will maintain higher pressure on the clutches in
> the transmission. Manny (the foremost TH425 expert) doesn't install
> kickdown switches in his rebuilds.
>
> 2. Don't try to make real power at low RPMs, particularly below 2000.
> Choose a lower gear. As Dick Paterson says to justify this recommendation,
> the oil pump is only moving at half the speed of the engine.
>
> 3. Therefore, if the grade is so steep that you can't maintain RPMs in the
> power band (2400 to 3600 RPMs, or thereabouts), slow down, manually
> downshift, and keep the engine in the power band.
>
> 4. At low speeds and while accelerating, the transmission will do the right
> thing.
>
> 5. From a stop, the stall slip of the torque converter will do what needs
> to be done.
>
> 6. The GMC isn't a race car.
>
> Rick "we have to be the drivetrain control computer" Denney
>
> On Mon, Dec 18, 2017 at 11:25 PM Vadim Jitkov

>
> >
> >
> > Here is a follow up question (let me know if I need to start a new thread
> > for this):
> > from the point of view of transmission, what is the best way to tackle
> > hills on the road? In the area where I live, we have significant grades on
> > nearly all our roads. We've got multiple grades of 3-4% in any direction
> > we get going and some very steep grades of 6-7%. I've read that its best to
> > slow down and downshift to "S" gear for tackling the grades. Should this
> > be done on all climbs or just on those very hard 6-7% grades? What about
> > driving in town (again lots of hills, but driving at 25-35 MPH)?
> >
>
> > --
> Rick Denney
> 73 x-Glacier 230 "Jaws"
> Off-list email to rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
Sometimes, it is the exhaust note that gets our attention in a GMC. Some of
them are quite "raspy" compared to our sound deadening environment in
modern automobiles. I compare modern automobiles to appliances. Open the
door, the light comes on. No driving pleasure here. Cars should not have
automatic transmissions or self starters or power windows. Wipers, ok.
Heaters, ok. Entertainment centers, nah. If you can't crank it, you don't
need to be driving it. (Grin)
Jim Hupy

> This makes perfect sense. Again it all comes down to engine RPMs on these
> big block engines. Just need to get comfortable at running it differently
> than what I'm used to.
>
>

> > 1. Don't use the automatic kickdown to choose a lower gear when climbing.
> > Shift down manually. This will maintain higher pressure on the clutches
> in
> > the transmission. Manny (the foremost TH425 expert) doesn't install
> > kickdown switches in his rebuilds.
> >
> > 2. Don't try to make real power at low RPMs, particularly below 2000.
> > Choose a lower gear. As Dick Paterson says to justify this
> recommendation,
> > the oil pump is only moving at half the speed of the engine.
> >
> > 3. Therefore, if the grade is so steep that you can't maintain RPMs in
> the
> > power band (2400 to 3600 RPMs, or thereabouts), slow down, manually
> > downshift, and keep the engine in the power band.
> >
> > 4. At low speeds and while accelerating, the transmission will do the
> right
> > thing.
> >
> > 5. From a stop, the stall slip of the torque converter will do what needs
> > to be done.
> >
> > 6. The GMC isn't a race car.
> >
> > Rick "we have to be the drivetrain control computer" Denney
> >
> > On Mon, Dec 18, 2017 at 11:25 PM Vadim Jitkov

> >
> > >
> > >
> > > Here is a follow up question (let me know if I need to start a new
> thread
> > > for this):
> > > from the point of view of transmission, what is the best way to tackle
> > > hills on the road? In the area where I live, we have significant
> grades on
> > > nearly all our roads. We've got multiple grades of 3-4% in any
> direction
> > > we get going and some very steep grades of 6-7%. I've read that its
> best to
> > > slow down and downshift to "S" gear for tackling the grades. Should
> this
> > > be done on all climbs or just on those very hard 6-7% grades? What
> about
> > > driving in town (again lots of hills, but driving at 25-35 MPH)?
> > >
> >
> > > --
> > Rick Denney
> > 73 x-Glacier 230 "Jaws"
> > Off-list email to rick at rickdenney dot com
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> --
> Vadim Jitkov
> '76 Glenbrook 26'
> Pullman, WA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Someone here once said, "Never go downhill in a GMC faster than you went up the hill..."
Meaning: don't let your downhill speed get away from you.
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
And generally go down in the same gear you went up (or would have to).
Also, if you're going down too fast, use the brakes briskly to slow below
the desired speed, THEN downshift to the gear that's needed to control the
speed.

Ken
​, Living in Flat Country but Been Up & Down Lots of Mountains,​
H.

> Someone here once said, "Never go downhill in a GMC faster than you went
> up the hill..."
> Meaning: don't let your downhill speed get away from you.
> --
> Bill Wevers GMC49ers, GMC Western States
> 1975 Glenbrook - Manny Powerdrive, OneTon
> 455 F Block, G heads
> San Jose
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Brakes only cool when they are not generating more heat than they are
giving up. DO NOT DRAG THEM. Apply them forcefully to lower the coach speed
below the safe posted speed, then, take your foot off the pedal. If
necessary, downshift and use engine braking in addition to braking effort.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

And generally go down in the same gear you went up (or would have to).
Also, if you're going down too fast, use the brakes briskly to slow below
the desired speed, THEN downshift to the gear that's needed to control the
speed.

Ken
​, Living in Flat Country but Been Up & Down Lots of Mountains,​
H.

> Someone here once said, "Never go downhill in a GMC faster than you went
> up the hill..."
> Meaning: don't let your downhill speed get away from you.
> --
> Bill Wevers GMC49ers, GMC Western States
> 1975 Glenbrook - Manny Powerdrive, OneTon
> 455 F Block, G heads
> San Jose
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Great explanation. Exactly what was going through my head when I asked about PD. I just didn't have experience or sufficient info to be able to
weigh all the factors on my own.

> Vadim. You covered the subject well. The T425 with a 3:07 FD, 14 inch tires, and a 4,000 lbs car was a good combination. GM had the peak HP for
> the 427, and 455 reached in the 3,600 to 4,200 RPM range. So higher RPM's in the 4200 range, and above isn't an issue. We have 16 inch tires, and
> 12,000 lbs as you covered. And a different cam profile. That's another can of worms. Till about 2003 we only had the 3:07, and 3:21. I think there
> was a 3:42 from Cinnabar? So the Power Drive was a way to get the RPM's up to get out of luging our engines years ago. But as you mentioned. The PD
> is adding more load on the T425. Then Jim K at Applied GMC came out with some great FD ratio choices up to a 4:10 ratio. These ratios ended the
> luging. And allow the engine/trans to work more efficiently. Some say the PD,or a lower FD ratio are the same. No. Not at all. Is the PD bad? No.
> It's better then nothing. In your situation. I'd leave things as they are till you have trans issues. Then change the FD ratio. I'm thinking of
> going to 4:10 from my 3:70. Towing, or not. I'd recommend 3:70. When I'm pulling my enclosed trailer with a car in it. A 78 Royale 403, and the 3:70
> FD. My GVW is about 21,000lbs. As a side note. My mileage went up with the 3:70. As to newer engines at 1500 RPM's at 65 MPH. Their design is
> another kind of animal. Bob Dunahugh Member GMCMI.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
As for newer vehicles, I've owned 11 pickup trucks since 2000, all Chev and GMC. The two 2005's I had were the last pickups that actually had some
getup and go, I still have one of those trucks. Its loaded for bear with a heavy-duty commercial capper and full of tools. I get whip-lash every time
I get in that truck.

I traded the other 2005 for a 2010 and all the trucks since have been lazy dogs. Sure they do about 1400rpm or less at 95km/hr. They switch in and out
of 4 cylinder mode. When you step on the gas it spends the next second or so deciding what gear its going to change to. I can visualize the little
hour-glass spinning in its control computers. Many times its feels like you are slowing rather than accelerating in that time.

When you flip the transmission into tow/haul mode, it becomes a different truck. Accelerating from stop with my utility trailer, it may wind up to
over 4,000 rpm in each gear (6 of them) before shifting. Depending on the load it may not get to the top gear and the rpms will be in the 2-3000 range
at highway speed. This is with a total load of maybe 7-8000lbs.

According to the trucks display. my 2005 gets about 13.2 litres/100km combined city/hyway. The 2016 and 2017 I have now get about 12.7litre/100km. I
don't think the new ones will get as much life as the 2005 with all the shifting they do.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
> As for newer vehicles, I've owned 11 pickup trucks since 2000, all Chev and GMC. The two 2005's I had were the last pickups that actually had some
> getup and go, I still have one of those trucks. Its loaded for bear with a heavy-duty commercial capper and full of tools. I get whip-lash every
> time I get in that truck.
>
> I traded the other 2005 for a 2010 and all the trucks since have been lazy dogs. Sure they do about 1400rpm or less at 95km/hr. They switch in and
> out of 4 cylinder mode. When you step on the gas it spends the next second or so deciding what gear its going to change to. I can visualize the
> little hour-glass spinning in its control computers. Many times its feels like you are slowing rather than accelerating in that time.
>
> When you flip the transmission into tow/haul mode, it becomes a different truck. Accelerating from stop with my utility trailer, it may wind up
> to over 4,000 rpm in each gear (6 of them) before shifting. Depending on the load it may not get to the top gear and the rpms will be in the 2-3000
> range at highway speed. This is with a total load of maybe 7-8000lbs.
>
> According to the trucks display. my 2005 gets about 13.2 litres/100km combined city/hyway. The 2016 and 2017 I have now get about
> 12.7litre/100km. I don't think the new ones will get as much life as the 2005 with all the shifting they do.

"That is what you have to expect for a new normal." - Guess who

That manufactures know all about this. They have to program the verhicles for emissions on a programed road test and CAFE. Pickups did not used to
be included in CAFE. But, when the overreaching government found out that people were buying pickups because they were still fun to driver, they put
an end to that as quickly as they could.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Wise words Bill Weaver...wish I had thought about that before I left Boone
NC a few years ago. Smoke at 6 wheels is a scary sight!

Mike in NM

> Brakes only cool when they are not generating more heat than they are
> giving up. DO NOT DRAG THEM. Apply them forcefully to lower the coach speed
> below the safe posted speed, then, take your foot off the pedal. If
> necessary, downshift and use engine braking in addition to braking effort.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>
> And generally go down in the same gear you went up (or would have to).
> Also, if you're going down too fast, use the brakes briskly to slow below
> the desired speed, THEN downshift to the gear that's needed to control the
> speed.
>
> Ken
> ​, Living in Flat Country but Been Up & Down Lots of Mountains,​
> H.
>
>

>
> > Someone here once said, "Never go downhill in a GMC faster than you went
> > up the hill..."
> > Meaning: don't let your downhill speed get away from you.
> > --
> > Bill Wevers GMC49ers, GMC Western States
> > 1975 Glenbrook - Manny Powerdrive, OneTon
> > 455 F Block, G heads
> > San Jose
> >
> > _______________________________________________
> > GMCnet mailing list
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> >
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--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

Life is too short to hold a grudge; slash some tires and call it even !