Home » Public Forums » GMCnet » [GMCnet] The power Drive dose ZERO for the trans load.
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356756 is a reply to message #356707] |
Tue, 14 July 2020 09:55   |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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Well, the input shaft to the transmission turns the same for a given road speed in a given gear regardless how it gets turned that amount. Thus the load on the clutches and hard parts is unchanged, is it not? Unless it were sentient, it has no knowledge of what's turning the input shaft, the internal load will be based solely on coach weight and speed, no?
Once the torque converter achieves stall speed, its load is determined by the coach speed and weight (load) plus slippage, is it not? Slippage at a given rate might be a bit higher at an increased speed, but I suggest the difference is negligible.
We have, however, increased engine speed for an identical load, which should reduce the torque requirement to the engine for that load should it not?
Would one of the gurus go through this and sustain or refute parts of it?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356760 is a reply to message #356756] |
Tue, 14 July 2020 10:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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The engines in our coaches are designed to produce lots of torque at a very
low rpm. That is why the GMC gets away with a 3:07 final drive ratio. That
parameter worked, up until the 403 came along. It is an over square engine
design. The bore is bigger than the stroke is long. It develops peak
horsepower and torque at a higher rpm range than the 455. It really
benefits from shorter final drive gearing. Very happy at 3400 rpm. The 455,
not so much.
But as it turns out, a long lever makes it much easier to lift a heavy
load, than a short lever does. Short lever is faster than a long lever. But
you cannot fool gravity. When you lift that same load 2 feet, makes no
difference whether the lever is long, or short. The same amount of work is
being done. That old formula F x D = W still applies. Do the math.
But, with transmissions, load and heating are reduced by using shorter
gearing.
Looks to me like your reasoning is sound, Johnny.
Jim Hupy
Salem, Oregon
On Tue, Jul 14, 2020, 7:58 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Well, the input shaft to the transmission turns the same for a given road
> speed in a given gear regardless how it gets turned that amount. Thus the
> load on the clutches and hard parts is unchanged, is it not? Unless it
> were sentient, it has no knowledge of what's turning the input shaft, the
> internal load will be based solely on coach weight and speed, no?
> Once the torque converter achieves stall speed, its load is determined by
> the coach speed and weight (load) plus slippage, is it not? Slippage at a
> given rate might be a bit higher at an increased speed, but I suggest the
> difference is negligible.
> We have, however, increased engine speed for an identical load, which
> should reduce the torque requirement to the engine for that load should it
> not?
> Would one of the gurus go through this and sustain or refute parts of it?
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me
> in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356768 is a reply to message #356760] |
Tue, 14 July 2020 11:57 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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The question is, where are you using that long lever? With the "Power
Drive", the long lever (and accompanying torque) is before the
transmission. A higher final drive ratio puts the "long lever" after the
transmission. But, the TH425 is such a robust unit that the little 10% or
so additional torque applied with chain multiplication probably isn't
significant. I ran power drive for several years after I first got the
GMC (and my son now runs the same unit in his 26'). I liked it because it
seemed quieter than any high ratio final drive I've experienced, including
the 3.55 I now run.
Ken H.
On Tue, Jul 14, 2020 at 11:25 AM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> The engines in our coaches are designed to produce lots of torque at a very
> low rpm. That is why the GMC gets away with a 3:07 final drive ratio. That
> parameter worked, up until the 403 came along. It is an over square engine
> design. The bore is bigger than the stroke is long. It develops peak
> horsepower and torque at a higher rpm range than the 455. It really
> benefits from shorter final drive gearing. Very happy at 3400 rpm. The 455,
> not so much.
> But as it turns out, a long lever makes it much easier to lift a heavy
> load, than a short lever does. Short lever is faster than a long lever. But
> you cannot fool gravity. When you lift that same load 2 feet, makes no
> difference whether the lever is long, or short. The same amount of work is
> being done. That old formula F x D = W still applies. Do the math.
> But, with transmissions, load and heating are reduced by using shorter
> gearing.
> Looks to me like your reasoning is sound, Johnny.
> Jim Hupy
> Salem, Oregon
>
> On Tue, Jul 14, 2020, 7:58 AM Johnny Bridges via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Well, the input shaft to the transmission turns the same for a given road
>> speed in a given gear regardless how it gets turned that amount. Thus
> the
>> load on the clutches and hard parts is unchanged, is it not? Unless it
>> were sentient, it has no knowledge of what's turning the input shaft, the
>> internal load will be based solely on coach weight and speed, no?
>> Once the torque converter achieves stall speed, its load is determined by
>> the coach speed and weight (load) plus slippage, is it not? Slippage at
> a
>> given rate might be a bit higher at an increased speed, but I suggest the
>> difference is negligible.
>> We have, however, increased engine speed for an identical load, which
>> should reduce the torque requirement to the engine for that load should
> it
>> not?
>> Would one of the gurus go through this and sustain or refute parts of it?
>>
>> --johnny
>> --
>> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
>> Braselton, Ga.
>> I forgive them all, save those who hurt the dogs. They must answer to me
>> in hell
>>
>>
>> _______________________________________________
>> 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
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356786 is a reply to message #356707] |
Wed, 15 July 2020 08:00 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Ken, I disagree that you increase torque to the transmission proper. As I suggested, the input shaft turns based on the road speed and load, amd the qorque required to turn it is determined only by these factors. Now, torque required to spin the converter is reduced by the increase in speed of the converter increasing to turn the transmission inpuit at a given speed. Is that what you meant?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356787 is a reply to message #356707] |
Wed, 15 July 2020 08:49 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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The changed chain ratio gives mechanical advantage to the engine and convertor. This compounds torque to rest of transmission and final and axles. Think of a 1 ton chain fall where the hand chain is easy to pull with one hand lifting heavy loads on the load chain, but requires a lot of chain through your hands to lift that heavy load only a few inches. For the same distance traveled (work done) there will be more engine power pulses contributing to the work, so less cylinder pressure on each cycle. Likewise there will be more maximum torque to the rest of the drive train at maximum cylinder pressures due to the compounding.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Wed, 15 July 2020 08:52] Report message to a moderator |
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356790 is a reply to message #356786] |
Wed, 15 July 2020 08:43 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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I would think the final drive solution is better because it increases the speed of the torque converter, keeping it in lockup better and reducing fluid temperatures.
I can't imagine the trans clutches slip at all in any case, and if they do you have a bigger issue!
________________________________
From: Gmclist on behalf of Johnny Bridges via Gmclist
Sent: Wednesday, July 15, 2020 8:00 AM
To: gmclist@list.gmcnet.org
Cc: Johnny Bridges
Subject: Re: [GMCnet] The power Drive dose ZERO for the trans load.
Ken, I disagree that you increase torque to the transmission proper. As I suggested, the input shaft turns based on the road speed and load, amd the
qorque required to turn it is determined only by these factors. Now, torque required to spin the converter is reduced by the increase in speed of the
converter increasing to turn the transmission inpuit at a given speed. Is that what you meant?
--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #356794 is a reply to message #356786] |
Wed, 15 July 2020 09:14 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Johnny,
Below the torque converter's lockup speed, I agree with you that the torque
transmitted to the transmission by the converter will be limited, and that
the constant road speed transmission load should be unchanged. But above
lockup, the load on the transmission, during ac/deceleration, will be
increased by the increased ratio of the output/input chain sprockets. This
analysis tends to confirm my contention that the TH425 is more than capable
of accepting the additional torque
Ken H.
On Wed, Jul 15, 2020 at 9:00 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Ken, I disagree that you increase torque to the transmission proper. As I
> suggested, the input shaft turns based on the road speed and load, amd the
> qorque required to turn it is determined only by these factors. Now,
> torque required to spin the converter is reduced by the increase in speed
> of the
> converter increasing to turn the transmission inpuit at a given speed. Is
> that what you meant?
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me
> in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
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Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #357650 is a reply to message #356707] |
Tue, 11 August 2020 20:17 |
rickmike
Messages: 252
Registered: September 2011
Location: United States
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Gentlemen,
Lets think about the torque from the other end.
Torque requirements at the output of the final drive is the same for pulling a grade at speed X or accelerating at Y Gs no matter what gearing is where in the transaxle. (F=ma)
Agreed?
With a numerically higher final drive the torque on the output shaft reduced for the needed torque requirement. Period. Therefore the torque on the gearset part of the transmission is reduced.
If you use the standard final drive and change the chain drive ratio, the torque on the gearset portion of the transmission is higher.
Rick Michelhaugh, ME
1974 26' Canyonlands
aka "The General"
Clinton, TN
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #357652 is a reply to message #357650] |
Tue, 11 August 2020 20:40 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Rick,
No argument here.
Ken H.
On Tue, Aug 11, 2020 at 9:18 PM Richard Michelhaugh via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Gentlemen,
>
> Lets think about the torque from the other end.
>
> Torque requirements at the output of the final drive is the same for
> pulling a grade at speed X or accelerating at Y Gs no matter what gearing is
> where in the transaxle. (F=ma)
> Agreed?
>
> With a numerically higher final drive the torque on the output shaft
> reduced for the needed torque requirement. Period. Therefore the torque on
> the
> gearset part of the transmission is reduced.
> If you use the standard final drive and change the chain drive ratio, the
> torque on the gearset portion of the transmission is higher.
>
> Rick Michelhaugh, ME
>
> --
> 1974 26' Canyonlands
> aka "The General"
> Clinton, TN
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #357653 is a reply to message #357650] |
Wed, 12 August 2020 06:48 |
6cuda6
Messages: 975
Registered: June 2019
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Agreed totaly as long as the converter is locked, stalled, hydraulically combined (how ever you want to say it).....if your converter is not stalled the whole deal changes.
rickmike wrote on Tue, 11 August 2020 21:17Gentlemen,
Lets think about the torque from the other end.
Torque requirements at the output of the final drive is the same for pulling a grade at speed X or accelerating at Y Gs no matterqq what gearing is where in the transaxle. (F=ma)
Agreed?
With a numerically higher final drive the torque on the output shaft reduced for the needed torque requirement. Period. Therefore the torque on the gearset part of the transmission is reduced.
If you use the standard final drive and change the chain drive ratio, the torque on the gearset portion of the transmission is higher.
Rick Michelhaugh, ME
Rich Mondor,
Brockville, ON
77 Hughes 2600
[Updated on: Wed, 12 August 2020 08:39] Report message to a moderator |
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| Re: [GMCnet] The power Drive dose ZERO for the trans load. [message #357671 is a reply to message #357661] |
Wed, 12 August 2020 15:37 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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Is there a lock-up converter for the 455?
On Wed, Aug 12, 2020 at 8:35 AM Mark Sawyer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Speaking of a lockup converter, has anyone seen or know anything about
> this:
>
>
> https://www.tciauto.com/maximizer-high-towing-torque-converter-1965-91-gm-th400-425-375-w-wide-bolt-pattern.html
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
>
> _______________________________________________
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--
*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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