gmclist@list.gmcnet.org

GMC Motorhome Discussion List

View all threads

Does "S" shift position have engine braking?

JH
James Hupy
Wed, Jul 28, 2021 3:01 AM

Originally the 442 indicated 4 barrel, 4 speed, and dual exhausts. Or
something like that. And yes indeed, it would turn the tires.  Worked on a
bunch of those. That 4 speed was almost indestructible.  Hell for strong.
Jim Hupy
Salem, Oregon

On Tue, Jul 27, 2021, 7:24 PM Keith V my427v8@hotmail.com wrote:

Ha ha ha, the Olds 442 did a LOT of engine braking, the rear tires
squealed like nothing Ive ever heard before.
But the transmission and all parts seemed no worse for wear!


From: Richard birchaven77@gmail.com
Sent: Tuesday, July 27, 2021 7:02 PM
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Does "S" shift position have engine braking?

Keith V wrote on Tue, 27 July 2021 16:22

I do t know, i remember getting reverse at 60mph. That was exciting!

Don't leave a guy hanging, Keith - what the hell happened???

Richard

--
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemonte waiting its turn


GMCnet mailing list
Unsubscribe or Change List Options:


GMCnet mailing list
Unsubscribe or Change List Options:

Originally the 442 indicated 4 barrel, 4 speed, and dual exhausts. Or something like that. And yes indeed, it would turn the tires. Worked on a bunch of those. That 4 speed was almost indestructible. Hell for strong. Jim Hupy Salem, Oregon On Tue, Jul 27, 2021, 7:24 PM Keith V <my427v8@hotmail.com> wrote: > Ha ha ha, the Olds 442 did a LOT of engine braking, the rear tires > squealed like nothing Ive ever heard before. > But the transmission and all parts seemed no worse for wear! > ________________________________ > From: Richard <birchaven77@gmail.com> > Sent: Tuesday, July 27, 2021 7:02 PM > To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> > Subject: [GMCnet] Re: Does "S" shift position have engine braking? > > Keith V wrote on Tue, 27 July 2021 16:22 > > I do t know, i remember getting reverse at 60mph. That was exciting! > > Don't leave a guy hanging, Keith - what the hell happened??? > > Richard > > -- > '77 Birchaven TZE...777; > '76 Palm Beach under construction; > ‘76 Edgemonte waiting its turn > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: >
DC
D C _Mac_ Macdonald
Wed, Jul 28, 2021 1:15 PM

I seem to remember that someone on this list
posted that the transmissions were tested during
development by jamming them into reverse at
highway speed.  Development continued until the
transmissions would survive that treatment.

D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com


From: James Hupy jamesh1296@gmail.com
Sent: Tuesday, July 27, 2021 22:01
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Does "S" shift position have engine braking?

Originally the 442 indicated 4 barrel, 4 speed, and dual exhausts. Or
something like that. And yes indeed, it would turn the tires.  Worked on a
bunch of those. That 4 speed was almost indestructible.  Hell for strong.
Jim Hupy
Salem, Oregon

On Tue, Jul 27, 2021, 7:24 PM Keith V my427v8@hotmail.com wrote:

Ha ha ha, the Olds 442 did a LOT of engine braking, the rear tires
squealed like nothing Ive ever heard before.
But the transmission and all parts seemed no worse for wear!


From: Richard birchaven77@gmail.com
Sent: Tuesday, July 27, 2021 7:02 PM
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Does "S" shift position have engine braking?

Keith V wrote on Tue, 27 July 2021 16:22

I do t know, i remember getting reverse at 60mph. That was exciting!

Don't leave a guy hanging, Keith - what the hell happened???

Richard

--
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemonte waiting its turn


GMCnet mailing list
Unsubscribe or Change List Options:


GMCnet mailing list
Unsubscribe or Change List Options:


GMCnet mailing list
Unsubscribe or Change List Options:

I seem to remember that someone on this list posted that the transmissions were tested during development by jamming them into reverse at highway speed. Development continued until the transmissions would survive that treatment. D C "Mac" Macdonald Amateur Radio K2GKK Since 30 November '53 USAF and FAA, Retired Member GMCMI & Classics Oklahoma City, OK "The Money Pit" TZE166V101966 '76 ex-Palm Beach k2gkk + hotmail dot com ________________________________ From: James Hupy <jamesh1296@gmail.com> Sent: Tuesday, July 27, 2021 22:01 To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> Subject: [GMCnet] Re: Does "S" shift position have engine braking? Originally the 442 indicated 4 barrel, 4 speed, and dual exhausts. Or something like that. And yes indeed, it would turn the tires. Worked on a bunch of those. That 4 speed was almost indestructible. Hell for strong. Jim Hupy Salem, Oregon On Tue, Jul 27, 2021, 7:24 PM Keith V <my427v8@hotmail.com> wrote: > Ha ha ha, the Olds 442 did a LOT of engine braking, the rear tires > squealed like nothing Ive ever heard before. > But the transmission and all parts seemed no worse for wear! > ________________________________ > From: Richard <birchaven77@gmail.com> > Sent: Tuesday, July 27, 2021 7:02 PM > To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> > Subject: [GMCnet] Re: Does "S" shift position have engine braking? > > Keith V wrote on Tue, 27 July 2021 16:22 > > I do t know, i remember getting reverse at 60mph. That was exciting! > > Don't leave a guy hanging, Keith - what the hell happened??? > > Richard > > -- > '77 Birchaven TZE...777; > '76 Palm Beach under construction; > ‘76 Edgemonte waiting its turn > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > _______________________________________________ GMCnet mailing list Unsubscribe or Change List Options:
L
Larry
Wed, Jul 28, 2021 4:18 PM

A number of years ago I talked to trans expert Manny Travao about this issue. He spoke to the parts in the trans that transmission braking can be hard
on. (can't remember what they are anymore) He advised me that brakes are cheaper and easier than transmissions to replace. So what I've done since is,
on long downhill interstate grades, I start at the top at 55mph and allow the coach to get to 65mph. I then brake to 55 and let it coast to 65. That
intermitant braking allows the brakes to cool between braking episodes while keeping speed reasonable. On long steep 2 lane grades, depending on the
grade and how winding the road is where I have to slow to low speeds, I will then use the trans to assist braking. JWID

Larry
78 Royale w/500 Caddy
Menomonie, WI.

A number of years ago I talked to trans expert Manny Travao about this issue. He spoke to the parts in the trans that transmission braking can be hard on. (can't remember what they are anymore) He advised me that brakes are cheaper and easier than transmissions to replace. So what I've done since is, on long downhill interstate grades, I start at the top at 55mph and allow the coach to get to 65mph. I then brake to 55 and let it coast to 65. That intermitant braking allows the brakes to cool between braking episodes while keeping speed reasonable. On long steep 2 lane grades, depending on the grade and how winding the road is where I have to slow to low speeds, I will then use the trans to assist braking. JWID -- Larry 78 Royale w/500 Caddy Menomonie, WI.
6
6cuda6@gmail.com
Wed, Jul 28, 2021 7:47 PM

Larry wrote on Wed, 28 July 2021 12:18

A number of years ago I talked to trans expert Manny Travao about this issue. He spoke to the parts in the trans that transmission braking can be
hard on. (can't remember what they are anymore) He advised me that brakes are cheaper and easier than transmissions to replace. So what I've done
since is, on long downhill interstate grades, I start at the top at 55mph and allow the coach to get to 65mph. I then brake to 55 and let it coast
to 65. That intermitant braking allows the brakes to cool between braking episodes while keeping speed reasonable. On long steep 2 lane grades,
depending on the grade and how winding the road is where I have to slow to low speeds, I will then use the trans to assist braking. JWID

Been doing that as well but this hill is a bad one.....its about 2.5 miles down and 14% grade.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

Larry wrote on Wed, 28 July 2021 12:18 > A number of years ago I talked to trans expert Manny Travao about this issue. He spoke to the parts in the trans that transmission braking can be > hard on. (can't remember what they are anymore) He advised me that brakes are cheaper and easier than transmissions to replace. So what I've done > since is, on long downhill interstate grades, I start at the top at 55mph and allow the coach to get to 65mph. I then brake to 55 and let it coast > to 65. That intermitant braking allows the brakes to cool between braking episodes while keeping speed reasonable. On long steep 2 lane grades, > depending on the grade and how winding the road is where I have to slow to low speeds, I will then use the trans to assist braking. JWID Been doing that as well but this hill is a bad one.....its about 2.5 miles down and 14% grade. -- Rich Mondor, Brockville, ON 77 Hughes 2600
RH
Richard H Staples
Thu, Jul 29, 2021 3:36 AM

Yes.

The THM400/425 has:

No engine braking in 1st gear drive range.
Engine braking in 1st gear Low range.
No engine braking in 2nd gear drive range.
Engine braking in 2nd gear "S" range
Engine braking (slightly) in 3rd gear.

HTH

Rick Staples,  '75 Eleganza, Johnstown, CO

"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill."  -Tolkien

Yes. The THM400/425 has: No engine braking in 1st gear drive range. Engine braking in 1st gear Low range. No engine braking in 2nd gear drive range. Engine braking in 2nd gear "S" range Engine braking (slightly) in 3rd gear. HTH -- Rick Staples, '75 Eleganza, Johnstown, CO "Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
BW
Bill Wevers
Thu, Jul 29, 2021 3:57 AM

According to my sources, putting the transmission in "S" engages
the band holding 2nd gear and elevates the hydraulic pressure.
Normally in "Drive" when shifting to second, there is a sprague
that engages in the forward direction(no engine braking).

When shifting to 3rd the sprague overruns and the direct clutch
holds the input and output shaft together.

The "L" works the same way only for first gear.
Here's a link to a diagram of the TH400 which is similar:
http://www.turbo-mopar.com/forums/attachment.php?attachmentid=39900&d=1338520896

Bill Wevers  GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose

According to my sources, putting the transmission in "S" engages the band holding 2nd gear and elevates the hydraulic pressure. Normally in "Drive" when shifting to second, there is a sprague that engages in the forward direction(no engine braking). When shifting to 3rd the sprague overruns and the direct clutch holds the input and output shaft together. The "L" works the same way only for first gear. Here's a link to a diagram of the TH400 which is similar: http://www.turbo-mopar.com/forums/attachment.php?attachmentid=39900&d=1338520896 -- Bill Wevers GMC49ers, GMC Western States 1975 Glenbrook - Manny Powerdrive, OneTon 455 F Block, G heads San Jose
JR
John R. Lebetski
Thu, Jul 29, 2021 2:12 PM

TH425 has no energy saving era freewheel clutches so it is engaged in all gears, except for converter slip  The friction material wear occurs only
during the shift events. Once in a lower gear, there should be no friction material slip  i drive it as if it were a manual in mountains.  If you rely
on brakes and you use them up with heat soak, then what?  I choose the lower gear preemptively, then apply brakes only as needed to limit engine
overspeed with very short applies and long off intervals. I beg to disagree with Manny here (and on disconnecting the GM designed kickdown which I
have connected as stock) as overheating brakes can warp drums and rotors and break down grease leading to future fails.  Remember that even Mobil 1
grease is only rated to 305F by Mobil.  My trans has just past 100K mark no problems.
The long grade you speak of at 14% is a first gear grade taken below 30 MPH. In S it will run away.

John Lebetski
Woodstock, IL
77 Eleganza II

TH425 has no energy saving era freewheel clutches so it is engaged in all gears, except for converter slip The friction material wear occurs only during the shift events. Once in a lower gear, there should be no friction material slip i drive it as if it were a manual in mountains. If you rely on brakes and you use them up with heat soak, then what? I choose the lower gear preemptively, then apply brakes only as needed to limit engine overspeed with very short applies and long off intervals. I beg to disagree with Manny here (and on disconnecting the GM designed kickdown which I have connected as stock) as overheating brakes can warp drums and rotors and break down grease leading to future fails. Remember that even Mobil 1 grease is only rated to 305F by Mobil. My trans has just past 100K mark no problems. The long grade you speak of at 14% is a first gear grade taken below 30 MPH. In S it will run away. -- John Lebetski Woodstock, IL 77 Eleganza II
JH
James Hupy
Thu, Jul 29, 2021 2:59 PM

Wear on the "S" clutches can be limited somewhat by matching engine RPM'S
to approximately what they would be in  "S" before you engage the
transmission manually.
If your coach lurches and rpm's climb suddenly, you just wore off some
clutch lining. Try to minimize that if possible.
Jim Hupy
Salem, Oregon

On Thu, Jul 29, 2021, 7:25 AM John R. Lebetski gransport7087@gmail.com
wrote:

TH425 has no energy saving era freewheel clutches so it is engaged in all
gears, except for converter slip  The friction material wear occurs only
during the shift events. Once in a lower gear, there should be no friction
material slip  i drive it as if it were a manual in mountains.  If you rely
on brakes and you use them up with heat soak, then what?  I choose the
lower gear preemptively, then apply brakes only as needed to limit engine
overspeed with very short applies and long off intervals. I beg to
disagree with Manny here (and on disconnecting the GM designed kickdown
which I
have connected as stock) as overheating brakes can warp drums and rotors
and break down grease leading to future fails.  Remember that even Mobil 1
grease is only rated to 305F by Mobil.  My trans has just past 100K mark
no problems.
The long grade you speak of at 14% is a first gear grade taken below 30
MPH. In S it will run away.

John Lebetski
Woodstock, IL
77 Eleganza II


GMCnet mailing list
Unsubscribe or Change List Options:

Wear on the "S" clutches can be limited somewhat by matching engine RPM'S to approximately what they would be in "S" before you engage the transmission manually. If your coach lurches and rpm's climb suddenly, you just wore off some clutch lining. Try to minimize that if possible. Jim Hupy Salem, Oregon On Thu, Jul 29, 2021, 7:25 AM John R. Lebetski <gransport7087@gmail.com> wrote: > TH425 has no energy saving era freewheel clutches so it is engaged in all > gears, except for converter slip The friction material wear occurs only > during the shift events. Once in a lower gear, there should be no friction > material slip i drive it as if it were a manual in mountains. If you rely > on brakes and you use them up with heat soak, then what? I choose the > lower gear preemptively, then apply brakes only as needed to limit engine > overspeed with very short applies and long off intervals. I beg to > disagree with Manny here (and on disconnecting the GM designed kickdown > which I > have connected as stock) as overheating brakes can warp drums and rotors > and break down grease leading to future fails. Remember that even Mobil 1 > grease is only rated to 305F by Mobil. My trans has just past 100K mark > no problems. > The long grade you speak of at 14% is a first gear grade taken below 30 > MPH. In S it will run away. > -- > John Lebetski > Woodstock, IL > 77 Eleganza II > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: >
KV
Keith V
Thu, Jul 29, 2021 2:59 PM

This is a good explaination.
I also think that manny means don't use the transmission to slow the vehicle from say 65 to 40, I don't think hes saying to use S to stay at 40mph


From: John R.Lebetski gransport7087@gmail.com
Sent: Thursday, July 29, 2021 9:12 AM
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Does "S" shift position have engine braking?

TH425 has no energy saving era freewheel clutches so it is engaged in all gears, except for converter slip  The friction material wear occurs only
during the shift events. Once in a lower gear, there should be no friction material slip  i drive it as if it were a manual in mountains.  If you rely
on brakes and you use them up with heat soak, then what?  I choose the lower gear preemptively, then apply brakes only as needed to limit engine
overspeed with very short applies and long off intervals. I beg to disagree with Manny here (and on disconnecting the GM designed kickdown which I
have connected as stock) as overheating brakes can warp drums and rotors and break down grease leading to future fails.  Remember that even Mobil 1
grease is only rated to 305F by Mobil.  My trans has just past 100K mark no problems.
The long grade you speak of at 14% is a first gear grade taken below 30 MPH. In S it will run away.

John Lebetski
Woodstock, IL
77 Eleganza II


GMCnet mailing list
Unsubscribe or Change List Options:

This is a good explaination. I also think that manny means don't use the transmission to slow the vehicle from say 65 to 40, I don't think hes saying to use S to stay at 40mph ________________________________ From: John R.Lebetski <gransport7087@gmail.com> Sent: Thursday, July 29, 2021 9:12 AM To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> Subject: [GMCnet] Re: Does "S" shift position have engine braking? TH425 has no energy saving era freewheel clutches so it is engaged in all gears, except for converter slip The friction material wear occurs only during the shift events. Once in a lower gear, there should be no friction material slip i drive it as if it were a manual in mountains. If you rely on brakes and you use them up with heat soak, then what? I choose the lower gear preemptively, then apply brakes only as needed to limit engine overspeed with very short applies and long off intervals. I beg to disagree with Manny here (and on disconnecting the GM designed kickdown which I have connected as stock) as overheating brakes can warp drums and rotors and break down grease leading to future fails. Remember that even Mobil 1 grease is only rated to 305F by Mobil. My trans has just past 100K mark no problems. The long grade you speak of at 14% is a first gear grade taken below 30 MPH. In S it will run away. -- John Lebetski Woodstock, IL 77 Eleganza II _______________________________________________ GMCnet mailing list Unsubscribe or Change List Options:
T
twlldeen@gmail.com
Thu, Jul 29, 2021 4:43 PM

When I go downhill in S using engine braking, it's a bit disconcerting listening to the pop-pop-pop from the engine ...normal or not?

Larry

Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses

When I go downhill in S using engine braking, it's a bit disconcerting listening to the pop-pop-pop from the engine ...normal or not? Larry -- Larry - Victoria BC - 1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system, 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses