Power difference between transmissions
#3095299
11/18/22 05:41 PM
11/18/22 05:41 PM
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volaredon
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I know that stick transmissions sap less power to operate from an engine than an auto trans. I wouldn't think the actual # of hp a given trans consumes would vary with a higher or lower HP engine. (Just throwing up a number, don't know how accurate it is) If for example a 727 eats up oh let's say 40hp pushing fluid, centrifugal force of the spinning clutch packs, planetaries etc... I'm guessing that it would be 40 hp whether behind a 100hp /6 or a 500 HP hemi, it would still consult that same 40 hp. Right? Would a shift kit alter that number? How bout a different stall speed converter? How about a lockup (or not?) Converter? How much more HP would a 727 consume vs say an a500 (early, non electronic)? How much more than an 833 od? Talking everything else the same with each variable listed. Same chassis, same engine, same fuel system, same gear, same tires, same driver, same roads and driving conditions? I have a d150 with a 727 and have an an a500 and an 833od that I "could" put in there. Given the current status of my project it wouldn't be much difference in cost or labor to go either way given what parts I have available at the moment. I'm trying to decide which way to go. Planning on 3 season daily driver, mostly country roads, lots of open road between... Truck is 2wd long bed and has a fresh, built up /6 and 3.23s in it. The 727 is it's original trans and is a lock up version. I'd need an adapter as was used in 60s /6 applications when used with a 727 to run the a500, otherwise everything else I'd need for whichever option I have on hand.
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Re: Power difference between transmissions
[Re: Cab_Burge]
#3095401
11/19/22 12:46 AM
11/19/22 12:46 AM
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Joined: Jan 2003
Posts: 20,335 Park Forest, IL
slantzilla
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Don, I don't know if you remember that orange D-150 I had, but when I got it all tuned up and running right it would knock down 23-24 mpg in OD with the 833OD trans.
Unless you rollerize it a 727 is gonna take X amount of power no matter what you do.
"Everybody funny, now you funny too."
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Re: Power difference between transmissions
[Re: volaredon]
#3095434
11/19/22 09:09 AM
11/19/22 09:09 AM
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
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I If for example a 727 eats up oh let's say 40hp pushing fluid, centrifugal force of the spinning clutch packs, planetaries etc... I'm guessing that it would be 40 hp whether behind a 100hp /6 or a 500 HP hemi, it would still consult that same 40 hp. Right?
Transmissions (and differentials) generally consume a percentage of the horsepower being transmitted through them, rather than a fixed amount like 40 HP. There is a “brake-away” torque that you can measure. This is what it takes to get an input shaft to barely move from 0 rpm. It is a small fixed horsepower loss, and depends mostly on drag of oil seals and such. The higher the gear reduction, the greater the percent of loss. a 2.96 ratio consumes a lower percentage than 4.56 ratio Straight cut gear teeth consume a lower percentage than beveled or helical gears, but straight cut makes more noise and can handle less peak power. The “low hanging fruit” of automatic transmission loss was going from a simple torque converter to a lockup type. Overdrive is a bit tricky, Adding a set of overdrive gears INCREASES power lost to friction, but shifting the engine to a lower rpm and raising intake manifold pressure has such a beneficial effect inside the gasoline engine that fuel economy of the vehicle improves. A light loaded pickup traveling 70 mph with the typical 0.67 ratio overdrive and 3.55 ratio differential would get a bit better fuel economy with 1.00 ratio transmission gear and differential ratio 2.37 (.67 x 3.55) but would get worse fuel economy towing a rated weight heavy trailer using its third gear ratio 1.3 with that 2.37 diff, instead of 1.00 gear and 3.55 diff. The 98% efficiency numbers of modern “automated manual transmissions” kind of stun me. I wonder: is that just in 1:1 top gear at some low rpm? Best case advertising hype that a vehicle seldom runs near?
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Re: Power difference between transmissions
[Re: 360view]
#3095436
11/19/22 09:53 AM
11/19/22 09:53 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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I If for example a 727 eats up oh let's say 40hp pushing fluid, centrifugal force of the spinning clutch packs, planetaries etc... I'm guessing that it would be 40 hp whether behind a 100hp /6 or a 500 HP hemi, it would still consult that same 40 hp. Right?
Transmissions (and differentials) generally consume a percentage of the horsepower being transmitted through them, rather than a fixed amount like 40 HP. There is a “brake-away” torque that you can measure. This is what it takes to get an input shaft to barely move from 0 rpm. It is a small fixed horsepower loss, and depends mostly on drag of oil seals and such. The higher the gear reduction, the greater the percent of loss. a 2.96 ratio consumes a lower percentage than 4.56 ratio Straight cut gear teeth consume a lower percentage than beveled or helical gears, but straight cut makes more noise and can handle less peak power. The “low hanging fruit” of automatic transmission loss was going from a simple torque converter to a lockup type. Overdrive is a bit tricky, Adding a set of overdrive gears INCREASES power lost to friction, but shifting the engine to a lower rpm and raising intake manifold pressure has such a beneficial effect inside the gasoline engine that fuel economy of the vehicle improves. A light loaded pickup traveling 70 mph with the typical 0.67 ratio overdrive and 3.55 ratio differential would get a bit better fuel economy with 1.00 ratio transmission gear and differential ratio 2.37 (.67 x 3.55) but would get worse fuel economy towing a rated weight heavy trailer using its third gear ratio 1.3 with that 2.37 diff, instead of 1.00 gear and 3.55 diff. The 98% efficiency numbers of modern “automated manual transmissions” kind of stun me. I wonder: is that just in 1:1 top gear at some low rpm? Best case advertising hype that a vehicle seldom runs near? This is correct. The drive train takes a percentage of power to run. That’s why on a chassis dyno the power consumption number goes up with power increases. It’s not a fixed number. Chassis dyno numbers get crapped on by many because they don’t understand how they work and how the power used to run the drive train is a percentage and not a fixed number.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Power difference between transmissions
[Re: volaredon]
#3095787
11/20/22 02:27 PM
11/20/22 02:27 PM
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Joined: Dec 2005
Posts: 1,169 Cruising!
QuickDodge
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It seems that manual transmissions make a more notable improvement in lower powered vehicles. This seems to be true for fuel economy, acceleration and the "fun to drive" factor.
Edit: Thanks to the guys who pointed out that automatics draw a percentage of power rather than a set amount. I did not know that!
Last edited by QuickDodge; 11/20/22 02:29 PM.
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Re: Power difference between transmissions
[Re: volaredon]
#3096616
11/23/22 06:16 PM
11/23/22 06:16 PM
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Ray S
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Newer auto transmissions are a lot better than the old slushy 727. The 727 rebuilt with torrington thrust bearing and moder TC is better and runs much cooler (so less waste) I went through a lot of this searching and then got a good deal on an 8HP70 from a newish wrecked RAM - the design wastes much less power with ingenious reduction in spinning gears etc. My concerns were freeway rpm reduction for mpg and noise (3300 down to 2400), and better acceleration. https://4wdlife.com/ram/8hp70-transmission"through intelligent engineering, modern materials, and electronic management system, the overall fuel economy is improved by 11% over old ZF 6HP units and 14% over manual transmissions."
Last edited by Ray S; 11/23/22 06:20 PM.
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Re: Power difference between transmissions
[Re: Ray S]
#3096629
11/23/22 07:28 PM
11/23/22 07:28 PM
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Posts: 2,381 ILLINOIS
volaredon
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I don't get the "percentage of power" thing. Don't make sense to me. You're not changing what parts weigh, (centrifugal force) or the fluid, it would seem it takes "x" quantity of power to run the trans. No matter what size engine is in front of it. More HP available, less percentage of the whole.
I asked what I did in the most general of terms, I'd think one 727 would eat up the same #of HP as the next, unless that "next" one was modified vs stock (rollerized, whatever) Or one 904 vs another, or one 500, or one a833od vs another one just like it, etc etc.
But more specifically in my exact case whatever trans I run on this project will be run by a built up /6. I don't see something like that "8hp-whatever" coming close to a possibility. If I decide the a500 is my trans of choice I'm gonna have to find a /6 to small block trans adapter as it is. The truck currently has it's original and working 727 in it. The only thing I have to do to that is find the leak(not the pan or the input or output shaft seal) and add a mild shift kit so I can stop the converter drain back situation it has. And drive the snot out of it from there. But I just got an 833od with flywheel, bell housing, pedals, linkage and everything I'd need to swap that in except for a new, fresh clutch which I believe I may have in the attic. And I have an a500 here too, that worked when pulled, that I'd rebuild before I use it just because of age and past maintenance being an unknown. But being a 500 is '904 based" it seems a downgrade vs a 727 in terms of durability. I don't have a 518 at present. I'd like to run something I have. If it's the 500 is definitely have to do some beefing up just for my own piece of mind.
If I'm gonna make a change from the 727 it's gonna be a change to the least power sucking option I have available and on hand.
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Re: Power difference between transmissions
[Re: volaredon]
#3096636
11/23/22 07:49 PM
11/23/22 07:49 PM
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Joined: Mar 2011
Posts: 3,178 Michigan
A727Tflite
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I don't get the "percentage of power" thing. Don't make sense to me. You're not changing what parts weigh, (centrifugal force) or the fluid, it would seem it takes "x" quantity of power to run the trans. No matter what size engine is in front of it. More HP available, less percentage of the whole.
I asked what I did in the most general of terms, I'd think one 727 would eat up the same #of HP as the next, unless that "next" one was modified vs stock (rollerized, whatever) Or one 904 vs another, or one 500, or one a833od vs another one just like it, etc etc.
But more specifically in my exact case whatever trans I run on this project will be run by a built up /6. I don't see something like that "8hp-whatever" coming close to a possibility. If I decide the a500 is my trans of choice I'm gonna have to find a /6 to small block trans adapter as it is. The truck currently has it's original and working 727 in it. The only thing I have to do to that is find the leak(not the pan or the input or output shaft seal) and add a mild shift kit so I can stop the converter drain back situation it has. And drive the snot out of it from there. But I just got an 833od with flywheel, bell housing, pedals, linkage and everything I'd need to swap that in except for a new, fresh clutch which I believe I may have in the attic. And I have an a500 here too, that worked when pulled, that I'd rebuild before I use it just because of age and past maintenance being an unknown. But being a 500 is '904 based" it seems a downgrade vs a 727 in terms of durability. I don't have a 518 at present. I'd like to run something I have. If it's the 500 is definitely have to do some beefing up just for my own piece of mind.
If I'm gonna make a change from the 727 it's gonna be a change to the least power sucking option I have available and on hand. A slant six will NEVER ruin an A500.
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Re: Power difference between transmissions
[Re: A727Tflite]
#3096653
11/23/22 09:28 PM
11/23/22 09:28 PM
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Joined: Jan 2008
Posts: 2,381 ILLINOIS
volaredon
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I've killed a couple behind 3.9s and being a /6 is an inline and not a V6 like a 3.9, I figured that the /6 would have more torque especially with the long stroke... If I go a500 it WILL get overhauled, with heavy duty clutches and steels, billet servos with double sealing rings and a mild shift kit like I had to do to the one in my last V6 Dakota got when I had to go inside that one because of the 2-3 shift flare it had.
But I'm wanting to know (relatively at least?) How much power each of these tranny's will suck away from that /6 as compared to each other. Again... Original to the truck... 727 lockup, then I have an a500 (hydraulic version, taken from a 91 318 Dakota) and a833 OD ... I have all here.//not looking for anything different than what I already have here, for that job.
And a place for each choice that doesn't wind up in the d150. It wouldn't hurt me to put the a833od in my volare either ... That one will be a stick when finished no matter what. Though I was thinking of a different stick trans for that car, I have this one now. And those were "stock" in that series of car, too. My particular one is a long tail, if a 727 would fit so will the long tail 4 speed ... Another auto to stick conversion any way, so I can work with the different shifter mount location....
Given those 3 choices which would you put into a D150?
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Re: Power difference between transmissions
[Re: volaredon]
#3096661
11/23/22 10:16 PM
11/23/22 10:16 PM
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Joined: Mar 2011
Posts: 3,178 Michigan
A727Tflite
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I've killed a couple behind 3.9s and being a /6 is an inline and not a V6 like a 3.9, I figured that the /6 would have more torque especially with the long stroke... If I go a500 it WILL get overhauled, with heavy duty clutches and steels, billet servos with double sealing rings and a mild shift kit like I had to do to the one in my last V6 Dakota got when I had to go inside that one because of the 2-3 shift flare it had.
But I'm wanting to know (relatively at least?) How much power each of these tranny's will suck away from that /6 as compared to each other. Again... Original to the truck... 727 lockup, then I have an a500 (hydraulic version, taken from a 91 318 Dakota) and a833 OD ... I have all here.//not looking for anything different than what I already have here, for that job.
And a place for each choice that doesn't wind up in the d150. It wouldn't hurt me to put the a833od in my volare either ... That one will be a stick when finished no matter what. Though I was thinking of a different stick trans for that car, I have this one now. And those were "stock" in that series of car, too. My particular one is a long tail, if a 727 would fit so will the long tail 4 speed ... Another auto to stick conversion any way, so I can work with the different shifter mount location....
Given those 3 choices which would you put into a D150?
Please explain - “killed”.
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Re: Power difference between transmissions
[Re: volaredon]
#3096680
11/23/22 11:12 PM
11/23/22 11:12 PM
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A727Tflite
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That’s not breaking the trans from power. Most likely a leak, low fluid, misadjusted throttle pressure, lack of maintenance (misadjusted band/s), etc. /6 wont “break” a 500.
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Re: Power difference between transmissions
[Re: volaredon]
#3096687
11/23/22 11:43 PM
11/23/22 11:43 PM
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Joined: Feb 2021
Posts: 157 PINE VALLEY
Ray S
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Original to the truck... 727 lockup, 727 with locking TC? Rare as hens teeth!
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