auto versus 6 speed

[hasselbach]

slippage can be the result of a poorly designed TC, whereas the fluid is doing no transference of energy (high stall, but no movement, typically due to an inefficent stator design, or fin angles that are inefficient) and fluid can be heated by shear and pressures. . good questions and points.

 

[jnelson]

2001 3500 CTD w/ 47re auto



Total mileage on transmission 433,000



Parts replaced :



Original TC at 80,000 installed BD TC and HP valvebody.



At 241,000 replaced with a DTT convertor, changed 2nd gear band and installed a shift kit.



Sold truck with 432,000+ miles with the original transmission.



Average load pulled - 21-25,000 pounds GCW

Heaviest load pulled - 52,000 GCW (floor tile)



I dont know of a better success story for a 47re or any other transmission.



I still bought a 6 speed in my new truck.

 

[Jeremiah]

I don't think so. Better get out a map.

You are absolutely correct. Sorry about that! Shows you how often I go that way. I just got back from Grand Junction via I-70 to Glenwood Springs, then to Minturn and Tennessee Pass, Leadville, Buena Vista and then home. That's the way I go mostly, unless I go Hoosier Pass to Breckenridge.

 

[Hohn]

slippage can be the result of a poorly designed TC, whereas the fluid is doing no transference of energy (high stall, but no movement, typically due to an inefficent stator design, or fin angles that are inefficient) and fluid can be heated by shear and pressures. . good questions and points.

Nope. This is simply false. Even the best designed TCs in the world will slip-- they MUST slip, or they wouldn't be torque converters.



Some converters obviously slip less than others, as those guys who try to street 8" converters that stall in the 5K range know. An example of a "better" converter imho is the 9. 5" converter that Dynamic Converters sells. It has a better stator design, and slips less because it's finned at zero-- according to Frank Lupo.



But the point here that's undeniable is that there is ALWAYS slippage in a fluid couple torque converter (ignoring lockup clutch effect). If there were no slippage, there would be no torque multiplication. Thus, we will ALWAYS have "fluid shearing and pressure".



Since torqe multiplication REQUIRES SLIPPAGE, a converter can be either efficient OR high-stall (i. e. , high torque multiplication).



I'd venture to say that if someone develops a high-torque multiplication converter that slips little (or none) and is efficient (as defined by the energy in vs energy out and no transmission heating), there will be quite a market for it in ALL applications. After all, few people shift just for the pleasure in most non-sporting applications.



If you've developed such a converter, by all means-- patent it and get rich.



There are certainly a lot of OEMs across the markets looking for such a design.



In the end, you "can't get something for nothing" and the advantages of the auto trans come at the price of mechanical efficiency.



Justin

 

[Jeremiah]

Efficiency v. inefficiency

Nope. This is simply false. Even the best designed TCs in the world will slip-- they MUST slip, or they wouldn't be torque converters.



Some converters obviously slip less than others, as those guys who try to street 8" converters that stall in the 5K range know. An example of a "better" converter imho is the 9. 5" converter that Dynamic Converters sells. It has a better stator design, and slips less because it's finned at zero-- according to Frank Lupo.



But the point here that's undeniable is that there is ALWAYS slippage in a fluid couple torque converter (ignoring lockup clutch effect). If there were no slippage, there would be no torque multiplication. Thus, we will ALWAYS have "fluid shearing and pressure".



Since torqe multiplication REQUIRES SLIPPAGE, a converter can be either efficient OR high-stall (i. e. , high torque multiplication).



I'd venture to say that if someone develops a high-torque multiplication converter that slips little (or none) and is efficient (as defined by the energy in vs energy out and no transmission heating), there will be quite a market for it in ALL applications. After all, few people shift just for the pleasure in most non-sporting applications.



If you've developed such a converter, by all means-- patent it and get rich.



There are certainly a lot of OEMs across the markets looking for such a design.



In the end, you "can't get something for nothing" and the advantages of the auto trans come at the price of mechanical efficiency.



Justin

I'm not sure, but I think Justin just clarified the question of which transmission is most efficient. Always knew it but didn't know why!

 

[hasselbach]

We've tested converters that had the EXACT stall speed (both were 11 inch units), both behind a BBC that was a stout 500 hp engine, both units stalled at 2,800 RPM, yet one plotted a torque curve over 150 ft lbs more than the other throughout the torque curve. Why? One unit was superior with fin angle and stator design, yet the other had mis matched parts. One converter through proper fin design was able to increase the torque output whereas the other poor design was simply shearing the fluid and not transferring torque. My statement is not false as Hohn seems to indicate. Slippage is required to create torque but you can have similar slippage factors (stall) and have widely varying outputs. Fluid shearing does not create torque Mr. Hohn, what creates torque is the pressure of the driven part of the converter (forward set of fins typically referred to as the pump) though a fluid loop, redirected by the stator. Similar to two fans facing each other. Depending how efficient the drive and driven fans are, results in the torque multiplication of the unit. The driving fan can be a very efficient 'pump' but if the driven fan is wrong, it doesn't matter how much power you put to it, it won't transfer the energy. But the stall can be exactly the point as say the efficient designed converter. And I assume Mr. Hohn you can tell us exactly what happens inside the TC when you reach full stall, right?



And lastly, slippage is not an evil outcome of the converter. Look at the gearing of the manual and auto transmission, yet both will put out similar torque numbers to the rear wheels, how? If the manual is something like 5. 8 to 1 and the auto is 2. 46 to 1, how can they achieve similar torque outputs? Its because of the 2 to 1 to 2. 5 to 1 Torque multiplication within the converter. Yet this number becomes closer to 1 to 1 (and evidentially 1 to 1 under full lock up) when the vehicle is in motion, explaining the smoother transition of power advantage the auto has.

 

[RustyJC]

Mr. Hasselbach,



Would you care to address the % mechanical efficiency (defined as [output BHP/input BHP] x 100 ) of an unlocked torque converter versus an engaged clutch assembly?



Rusty

 

[hasselbach]

Mr. Hasselbach,



Would you care to address the % mechanical efficiency (defined as [output BHP/input BHP] x 100 ) of an unlocked torque converter versus an engaged clutch assembly?



Rusty

why? that's comparing apples to oranges. Howabout a locked converter to a locked clutch? that's apples to apples. and its been proven that a locked auto transmission is equal to a manual transmission, the pump parasitic loss is offset by the inefficient design within the manual's multi geared engagement in direct 1 to 1 9linear vs. non-linear powerflow). I've seen on transmission dynos that showed automatics actually absorbing less hp than a manual of equal size and capacity.



but since you asked, here goes. if your torque converter input speed is say 3000 rpm with say 200 ft lbs of torque, and your output speed is 1500 rpm, and you know the torque multiple at maximum stall is say 2 to 1, then your output will be in the area of say 400 ft lbs of torque. but, here's the catch, your hp hasn't changed in either number (horse power being defined at the amount of work that you can do over a set time period, originally being defined as a horse lifting a certain amount of weight in one minute, or to convert to automotive, torque times rpm, divided by 5252), thus you can do the same amount of work for either scenario (3000 rpm, 200 ft lbs or 1500 rpm, 400 ft lbs, both equal 114 hp). you have to stop thinking of slippage as a bad thing, but recognize that slippage results in creating the increased torque multiplication of the output.



Now with your manual trans, the same holds true if you say have a 2 to 1 gear ratio, but instead of fluid coupling, you have a mechanical means of multiplication, ie gears,



this explains the deeper ratios for the manual unit since the clutch does not create torque, even with slippage.

 

[RustyJC]

Therefore, in any condition but torque converter lockup, the inherent slippage of the unlocked torque converter means that the automatic transmission will have a lower overall mechanical efficiency than a manual transmission, right?



(Thanks for the explanation, but I have a passing familiarity with the definitions of mechanical efficiency, horsepower and torque. As you know, gearing {or, in your case, a torque converter} can multiply torque, but not BHP, and any BHP lost in the torque multiplication process as heat or other losses is lost mechanical efficiency. )



Rusty

 

[hasselbach]

Therefore, in any condition but torque converter lockup, the inherent slippage of the unlocked torque converter means that the automatic transmission will have a lower overall mechanical efficiency than a manual transmission, right?



(Thanks for the explanation, but I have a passing familiarity with the definitions of mechanical efficiency, horsepower and torque. As you know, gearing {or, in your case, a torque converter} can multiply torque, but not BHP, and any BHP lost in the torque multiplication process as heat or other losses is lost mechanical efficiency. )



Rusty

Based on your post above, I don't think you do have a "passing familiarity", more of a RustyTC on the issue . I never said TC's increase HP did I? How much efficiency does a manual transmission have when you shift? Two areas of inefficiency:



1, when shifting and the clutch is pushed in, just how much torque are you transferring then? (ah, 'nothing' is the correct answer)

2. The rpm drop between gears can be dramatic, sometimes over 100% (first to second for example), how efficient is that? Manuals may be great for running pumps at continuous rpms, but with non static applications, the auto is superior.

The correctly sized TC can keep the engine in the heart of the torque curve resulting in by far; superior torque management, fuel usage and overall efficiency.



check and checkmate.....



oh, and try to tell me why this doesn't make sense. We all know that engines do not have linear torque curves, right? Torque curves all have a peak (sometimes two), with lower amounts prior to the peak and after the peak, right? (its a given). Thus, tell me which makes more efficiency sense for say a diesel engine that say creates the most torque at 1900 rpm and is accelerating a load to highway speeds:



1, slip the clutch, lug the motor, 800 rpm..... shift at 2800 (pause, no torque transferred), now back to 1400 rpm... . keep going, faster faster... okay, back to 2800 rpm, shift, (pause, no torque transferred) , back to 1600 rpm... . okay, keep going... . back to 2800 rpm, time to shift again (pause, no torque transferred)... Yeah, real efficient isn't it? Up and down the torque curve, not to mention the pauses while you have to shift. .



2, push down on the accelerator, engine goes to 1900 then holds, truck starts to move forward, goes a lot farther than the manual since the converter continually tightens up, by the time the manual is in third and ready to hit fourth, the auto hits 2400 rpm, BAM, second gear in a nano second, drops to 1900 rpm... . accelerating to 2350, BAM, third gear, back to 1900. . oh wait, gotta hit the brakes hard, that dodge in front of me is SO SLOW, too bad he got a stick... Keeping the engine closer in the middle of the torque curve is where its at RustyTC. The best option would be a TC and transmission that keep the engine like above at 1900 or so continuously.





checkers anyone?

 

[Archive]

2001 3500 CTD w/ 47re auto



Total mileage on transmission 433,000



Parts replaced :



Original TC at 80,000 installed BD TC and HP valvebody.



At 241,000 replaced with a DTT convertor, changed 2nd gear band and installed a shift kit.



Sold truck with 432,000+ miles with the original transmission.



Average load pulled - 21-25,000 pounds GCW

Heaviest load pulled - 52,000 GCW (floor tile)



I dont know of a better success story for a 47re or any other transmission.



I still bought a 6 speed in my new truck.

432,000+ miles on the original clutch packs? :--) Sure this list is complete?

 

[RustyJC]

Based on your post above, I don't think you do have a "passing familiarity".

I love ad hominem attacks! What specifically is incorrect in the post above?

I never said TC's increase HP did I? How much efficiency does a manual transmission have when you shift? Two areas of inefficiency:



1, when shifting and the clutch is pushed in, just how much torque are you transfering then (ah, not too much is the correct answer)

Red herring. The subject I was discussing is mechanical efficiency. How much BHP (and, thus, fuel) is being consumed during a zero-throttle shift with a manual transmission?

2. The rpm drop between gears can be dramatic, sometimes over 100% (first to second for example), how efficient is that? Manuals may be great for running pumps at continuous rpms, but with non static applications, the auto is superior.

In terms of fuel consumption the net variance with engine speed will depend on the engine's BSFC curve, right?

3. the correctly size TC can keep the engine in the heart of the torque curve resulting in buy far superior torque management.



check and checkmate.....

Not at all. In terms of overall fuel consumption, it will depend upon the variations in the BSFC curve as engine speed varies (advantage - properly designed unlocked torque converter) versus the losses incurred due to torque converter slippage (advantage - manual transmission). If you want the fuel consumption advantage achieved by holding the engine RPM at its BSFC "sweet spot" without the losses incurred by an unlocked torque converter, let's talk about continuously variable transmissions (CVTs).



Rusty

 

[Archive]

Chevy's Allison is an impressive piece of technology. The following link has some very interesting info on its capabilities:



http://service.gm.com/gmtechlink/images/issues/aug04/TLaug04e.html



As with everything, this capability has its benefits and drawbacks. In town and in traffic it's marvellous. And for racing, the robo-shifter and it's easy and consistent launch can't be beat.



But put me thirty miles into the back country, alone, in a part of the country where the weather and terrain can kill you, give me a manual anytime.



I've had several automatic transmission failures over the years. In each case, the vehicle lost all forward capability. I've also had a clutch explosion and gear failures with manuals, but the clutch stayed tied up and other gears worked and I got back home.



It's real hard to kill a manual.



I also spend a lot of time hauling road base up a mountain on a dirt road in 4WD. I suspect the 48re would overheat in this application because it won't lock up at the 10 - 15 mph I have to travel on this road. The Allison might be OK because it locks up all the way from 2nd gear to 5th, and 1st is much lower than the 48re.



Across the automotive industry, you will generally find that in any particular make or model of car, the manual version will have a higher mileage rating than the auto. If that wasn't the case, the manual would not be offered, particularly because it is more difficult to certify for emissions.

 

[hasselbach]

RustyTC, for your benefit



Try to tell me why this doesn't make sense. We all know that engines do not have linear torque curves, right? Torque curves all have a peak (sometimes two), with lower amounts prior to the peak and after the peak, right? (its a given). Thus, tell me which makes more efficiency sense for say a diesel engine that say creates the most torque at 1900 rpm and is accelerating a load to highway speeds:



1, slip the clutch, lug the motor, 800 rpm..... shift at 2800 (pause, no torque transferred), now back to 1400 rpm... . keep going, faster faster... okay, back to 2800 rpm, shift, (pause, no torque transferred) , back to 1600 rpm... . okay, keep going... . back to 2800 rpm, time to shift again (pause, no torque transferred)... Yeah, real efficient isn't it? Up and down the torque curve, not to mention the pauses while you have to shift. .



2, push down on the accelerator, engine goes to 1900 then holds, truck starts to move forward, goes a lot farther than the manual since the converter continually tightens up, by the time the manual is in third and ready to hit fourth, the auto hits 2400 rpm, BAM, second gear in a nano second, drops to 1900 rpm... . accelerating to 2350, BAM, third gear, back to 1900. . oh wait, gotta hit the brakes hard, that dodge in front of me is SO SLOW, too bad he got a stick... Keeping the engine closer in the middle of the torque curve is where its at RustyTC. The best option would be a TC and transmission that keep the engine like above at 1900 or so continuously.





checkers anyone?

 

[RustyJC]

What's the cost in mechanical losses incurred by the torque converter in order to hold the engine in the narrower RPM band you describe? There's no free lunch, here. When the clutch is engaged and transmitting torque, its (i. e. , the clutch's) mechanical efficiency is basically 100% What is the torque converter's mechanical efficiency when it's unlocked as the truck is accelerating? There's a reason automatics have radiator tank and oil-to-air coolers - where do you think those BTU's that are being dumped are coming from? Ultimately - the combustion of #2 diesel.



Let's boil it all down to this. With everything else equal, which is going to be more fuel efficient - the torque converter-equipped 4 speed automatic, or the manual clutch-equipped 6 speed manual? Wanna take bets?



Rusty

 

[hasselbach]

What's the cost in mechanical losses incurred by the torque converter in order to hold the engine in the narrower RPM band you describe? There's no free lunch, here. When the clutch is engaged and transmitting torque, its (i. e. , the clutch's) mechanical efficiency is basically 100% What is the torque converter's mechanical efficiency when it's unlocked as the truck is accelerating? There's a reason automatics have radiator tank and oil-to-air coolers - where do you think those BTU's that are being dumped are coming from? Ultimately - the combustion of #2 diesel.



Let's boil it all down to this. With everything else equal, which is going to be more fuel efficient - the torque converter-equipped 4 speed automatic, or the manual clutch-equipped 6 speed manual? Wanna take bets?



Rusty

sure, I'll take the bet. . Its real fuel efficient accelerating a 100 lbs flywheel and other reciprocating parts over and over and over between each shift, isn't it? Whereas the automatic can stay at or very close to the torque peak of the motor 100% of the time. . Once locked up the auto has less drag than the manual and creates less heat, why? In direct drive, there is no gear shearing since the planetarys are locked up... yep, nothing other than a small pump is creating any heat. I can't say that for your manual that has multiple gear engagement in direct drive, with something like 16 gears all shearing fluid creating heat... hmmm, didn't think about that one did you? :-laf



Heat creation? Have you tapped into your rear end and manual transmission and seen the temps they put out? Sure the automatic creates some heat, so what? Put a cooler on it and relax, you are making something out of the heat issue more than is it.

 

[hasselbach]

Chevy's Allison is an impressive piece of technology. The following link has some very interesting info on its capabilities:



http://service.gm.com/gmtechlink/images/issues/aug04/TLaug04e.html



As with everything, this capability has its benefits and drawbacks. In town and in traffic it's marvellous. And for racing, the robo-shifter and it's easy and consistent launch can't be beat.



But put me thirty miles into the back country, alone, in a part of the country where the weather and terrain can kill you, give me a manual anytime.



I've had several automatic transmission failures over the years. In each case, the vehicle lost all forward capability. I've also had a clutch explosion and gear failures with manuals, but the clutch stayed tied up and other gears worked and I got back home.



It's real hard to kill a manual.



I also spend a lot of time hauling road base up a mountain on a dirt road in 4WD. I suspect the 48re would overheat in this application because it won't lock up at the 10 - 15 mph I have to travel on this road. The Allison might be OK because it locks up all the way from 2nd gear to 5th, and 1st is much lower than the 48re.



Across the automotive industry, you will generally find that in any particular make or model of car, the manual version will have a higher mileage rating than the auto. If that wasn't the case, the manual would not be offered, particularly because it is more difficult to certify for emissions.

It's real hard to kill a manual. REALLY? Well to what are the benefits of the manual on the other drivetrain parts?

My son and I do the Rubicon trail every year, and belong to a local 4x4 club here that does weekend jaunts to the mojave desert, and I'd say 90% of the trucks are automatics and 90% of all breakage we see is usually u-joints, driveshafts etc. . and the majority of those breaking are powered by manuals. I can't recall a single incident in a very long time where the automatic failed at an event. And some of these hill climbs are EXTREME and super hard on the drivetrain.

 

[RustyJC]

Once locked up... .

All the torque converter's advantages of torque multiplication and narrower RPM bands you've been preaching disappear, don't they?

Heat creation? Have you tapped into your rear end and manual transmission and seen the temps they put out? Sure the automatic creates some heat, so what? Put a cooler on it and relax, you are making something out of the heat issue more than is it.

As a fellow mechanical engineer, you are certainly familiar with a system heat balance analysis. It's an integral part of the R&D process on the engines and gas turbines our company produces.



The heat created by the torque converter and rejected to the cooling system (by the radiator tank cooler) and directly to the atmosphere (by the oil-to-air cooler) is not a non-issue - it must be accounted for as part of the heat rejection losses in the overall analysis of the mechanical efficiency of the engine/transmission system. If the automatic transmission with its unlocked torque converter is rejecting more BTUs per minute than the manual transmission with its manual clutch, then its thermal losses are higher, and ultimately its mechanical efficiency ([output BHP/input BHP] x 100) will be lower.



Rusty

 

[hasselbach]

Rusty, you seem pretty good at taking partial sentences of mine to prove your unsupported points. The TC locks up when nearing the final drive engagement ratio, it's unlocked to add additional torque when needed. So what's your point? Its doing what its supposed to do. I can have a TC set up that gives me a overall ratio of say 6 to 1 when producing torque, and once locked up yield 2. 46 to one. Seem superior to having to shift 1 to 2 times. All while keeping the engine within its torque curve, something the inefficient manual can't do.



Why don't you comment on having to accelerate the 100 lbs flywheel numerous times while shifting? You seems to miss that very important point, didn't you? I can't see how efficient it is to expend energy to accelerate a mass over and over again, can you?



And this heat issue you keep bringing up? Do you realize the water to oil cooler is there to INTRODUCE heat into the transmission? Not the other way around. For those that live in the colder climates, heat is added to the transmission. The water to oil unit is not intended to remove heat from the transmission, that's the air to oil unit in the front. I've removed plenty of the oil to water units and found a 30 to 50 degree DROP of transmission temperatures immediately. I just don't recommend it to those in the cold climates.

 

[RustyJC]

All while keeping the engine within its torque curve, something the inefficient manual can't do.

Actually, as configured for towing, my engine has a significant torque rise but a fairly flat BHP curve of over 300 RWHP from 2200 RPM to 3200 RPM. Therefore, keeping the engine operating in this range maximizes the area under the time/BHP curve.

Why don't you comment on having to accelerate the 100 lbs flywheel numerous times while shifting? You seems to miss that very important point, didn't you? I can't see how efficient it is to expend energy to accelerate a mass over and over again, can you?

As you know, the amount of energy expended to accelerate the flywheel is a function of the time required for the engine to pull from (in my case) about 2000 RPM to 2800 RPM. In the lower gears, this argument might have some validity - in the higher gears, however, this loss isn't significant.

And this heat issue you keep bringing up? Do you realize the water to oil cooler is there to INTRODUCE heat into the transmission? Not the other way around. For those that live in the colder climates, heat is added to the transmission. The water to oil unit is not intended to remove heat from the transmission, that's the air to oil unit in the front. I've removed plenty of the oil to water units and found a 30 to 50 degree DROP of transmission temperatures immediately. I just don't recommend it to those in the cold climates.

With all respect, this statement makes me question your real world familiarity with the V-10 and Cummins/47RE and 48RE application in the Dodge Ram. In heavy towing applications, automatic transmission equipped trucks are more prone to higher coolant temperatures than manual transmission trucks, especially on long grades with the torque converter unlocked. In the case of my prior V-10/47RE truck, I solved a chronic high coolant temperature problem when towing our 5th wheel RV in Houston traffic during the summers (i. e. , conditions where there is a large average difference in RPM between the pump and turbine) by adding a 2nd oil-to-air cooler ahead of (i. e. , upstream of) the radiator tank cooler, thus reducing the amount of heat transferred from the ATF to the coolant. Therefore, one cannot state that heat transfer is always from the coolant to the ATF - such is not the case.



Rusty