Options for Compounds with a 38R

[PowerstrokeJunkie]

You always have the best explanations to and viewpoints on these things, kudos

 

[Jake]

I think a single axle tractor will be in my future if the big dana sh*ts on this 550 again. Then I'll just short-trip the 550 to deliver equipment and use the tractor for hauling hay and long trips with equipment.

I have been thinking about doing the same thing, but here now you may as well make it full commercial, the "not for hire" "recreational vehicle" is not flying down here anymore. I was bringing a load of brood mares down from my buddies place in OK and as soon as I got back into TX I got pulled over by the DOT guy and he had us on side of the road for 4 hours doing all the checks on the truck. How I didn't have a horse tie up or die while we sat there is 105 degree weather. The truck has "private not for hire" on it and has the US DOT # on it, there has been a lot more of this happening down here like that. After that I am 99% against getting one.

 

[DocBar]

No matter how you slice it, power is what is burning things up at steady-state towing duty. The driveline simply cannot transmit but a finite amount of power without overheating. Increase the rpm and lower the torque and the tooth to tooth pressure would decrease, but bearing and tooth friction would go up because of the rpm and you're right back to square one. Decrease the rpm and increase the torque and bearing and tooth friction comes down with lower rpm, but tooth to tooth and bearing pressure goes up because of the greater torque loads and again, right back to square one unless the power comes down. If there was say a 16% parasitic loss through the driveline... and you were putting 300hp to the ground, then that means you were making 357hp at the crank and 57hp was being converted to heat, sound and vibration through the driveline.

57hp is 42,522watts. Imagine a 45,000watt heater in your trans fluid, blasting your u-joints and your diff fluid, gears and bearings.

And amazingly, the drivetrain seems capable of sustaining it.

Now bump it up to 400rwhp, and that turns into 76hp or 56,696watts of power doing nothing but churning and burning bearings, gears and u-joints.

500rwhp it becomes 95hp, or 70,800watts...


Meanwhile, back at the 200 or so the truck was desgined for, it's only 38hp.

At 500rwhp the parasitic load on the driveline is 2.5 times the design load. As long as you don't stay in the power for too long, nothing will get too hot. You can run your hand over a candle flame quickly with no problems, but if you leave it there for a moment, things get ugly.

Out on the interstate for hour after hour, things get ugly up under a superduty somewhere around ~300 wheel in my experience.

I deal with electric motors at work and I follow what you're saying about the heat, but you also have a ~60 mph wind blowing over these diffs and gear boxs. How is that different than a 50hp electric motor running all day with a small cooling fan attached to the non-drive end? These motors run at or near full capacity for months on end with no heating issues. Could it be the oil holding heat better than air does?

I'm not arguing with you, just asking and trying to get it right in my head.

 

[Jake]

That would be a fun heat transfer problem. Its just figuring out how much goes where. How much credit you can take for the air circulation, how much actual air movement do you have in some key areas. The oil has a higher specific heat so it will take more energy to heat the and more to take it away then air. With the coolers in the front of the truck for the transmissions there is some heat transfer there that I think would be better than just the case being the heat sink. I remember when I was trying to tow in the high 300's into the low 400's I experienced the same problems of just cooking all the driveline components. On the electric motors you just have the two bearings as your main frictional loss, there is some loss in windings and wind drag. But a super high E TEFC motor efficiency is in the 90% range, with the driveline parts there are just so many parts that are metal on metal friction especially with the use of ATF in the manual transmissions I think that is a double edge sword less fluid friction but more part to part friction. Same thing here we have electric motors and pumps that run for 18months strait I think it all boils down to the power transfer parts sized better for the input power and required power.

 

[Charles]

I have been thinking about doing the same thing, but here now you may as well make it full commercial, the "not for hire" "recreational vehicle" is not flying down here anymore. I was bringing a load of brood mares down from my buddies place in OK and as soon as I got back into TX I got pulled over by the DOT guy and he had us on side of the road for 4 hours doing all the checks on the truck. How I didn't have a horse tie up or die while we sat there is 105 degree weather. The truck has "private not for hire" on it and has the US DOT # on it, there has been a lot more of this happening down here like that. After that I am 99% against getting one.

I just drove ~5 hours through two states in a tandem tractor with a tri-axle lowboy behind me, so the legality of it isn't a problem. I have been trying to stick to the 550 for ease of use more than anything. Pulling into a food joint, not having to weigh in, getting into and out of farm roads, so on and so forth.

That's why I would use a single axle tractor instead of our tandem if I did it, for maneuverability, although I'd have to weigh everywhere I went then, but if this 550 craps something in the driveline out again, I'll just deal with it for hay loads and long haul equipment loads instead of pushing on this pickup any more.

 

[Charles]

I deal with electric motors at work and I follow what you're saying about the heat, but you also have a ~60 mph wind blowing over these diffs and gear boxs. How is that different than a 50hp electric motor running all day with a small cooling fan attached to the non-drive end? These motors run at or near full capacity for months on end with no heating issues. Could it be the oil holding heat better than air does?

I'm not arguing with you, just asking and trying to get it right in my head.

The 57hp is just the parasitic load. The driveline itself would actually be taking the full 357....

And due to what you described above.... for the most part it seems to take that much. But the durability goes down sharply beyond that in my experience.

For reference.... go take a look at some tow vehicles designed to be putting 300hp to the ground continuously. You're immediately going to be looking at semi trucks. Notice the size of the transmissions, axles and driveshafts and compare that to your superduty.

The difference is staggering.

 

[Jake]

We were all legal, its still just the hassle of the DOT dicks, the fat bitch that pulled me over that day just dragged her feet though everything, I was nice to her the first hour then I was having a real hard time since the horses were just cooking in the trailer. Weighing in TX and OK actual weigh stations are far and few between. They do it when they pull you over. I am just going to keep the HP down and manage my weight to stay in a pickup.

I just drove ~5 hours through two states in a tandem tractor with a tri-axle lowboy behind me, so the legality of it isn't a problem. I have been trying to stick to the 550 for ease of use more than anything. Pulling into a food joint, not having to weigh in, getting into and out of farm roads, so on and so forth.

That's why I would use a single axle tractor instead of our tandem if I did it, for maneuverability, although I'd have to weigh everywhere I went then, but if this 550 craps something in the driveline out again, I'll just deal with it for hay loads and long haul equipment loads instead of pushing on this pickup any more.

 

[PowerstrokeJunkie]

this is a drivetrain designed for 330hp.

 

[Jake]

this is a drivetrain designed for 330hp.

At what grvw and gcrw ?

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[PowerstrokeJunkie]

33,000

 

[DocBar]

I guess I need to crawl under a 2012 F250. It's rated at 400hp. I wonder how big that drivetrain is. oke:

 

[Buffalo444]

I guess I need to crawl under a 2012 F250. It's rated at 400hp. I wonder how big that drivetrain is. oke:

That's the difference between "constant" and "peak"

 

[DocBar]

That's the difference between "constant" and "peak"

Hence the oke:

 

[TyCorr]

That 400 hp truck is probably putting 250 to the rears while towing. Maybe less? I don't know but there is no way my 400hp dmax is putting 4hundy to the 'phalt because my 7.3 with 175/100's and a 38r in my race tune is 400 + a hair. It whips the piss out of the chebby but not in that race tune, in a tow file that is sub 300. And the superduty is.lifted on 35s. I've never towed with a 6.4 or 6.7 powerstroke though :shrug:

 

[Jomax]

That 400 hp truck is probably putting 250 to the rears while towing. Maybe less? I don't know but there is no way my 400hp dmax is putting 4hundy to the 'phalt because my 7.3 with 175/100's and a 38r in my race tune is 400 + a hair. It whips the piss out of the chebby but not in that race tune, in a tow file that is sub 300. And the superduty is.lifted on 35s. I've never towed with a 6.4 or 6.7 powerstroke though :shrug:

See this is what has me stumped. The new trucks have 400hp at the crank, lets say they loose 60hp when it finally hits the ground. It still has 340hp to the wheels. They're rated to tow 20k In a DRW platform and they're holding together?? Does the engine limit HP when it feels a load?


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2000 Black DRW F-350
2012 pearl white Focus

 

[TyCorr]

See this is what has me stumped. The new trucks have 400hp at the crank, lets say they loose 60hp when it finally hits the ground. It still has 340hp to the wheels. They're rated to tow 20k In a DRW platform and they're holding together?? Does the engine limit HP when it feels a load?


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TapTalk
2000 Black DRW F-350
2012 pearl white Focus

Push the tow/haul button and it changes the way it drives. Who hammers the pedal to pull a trailer full of something? Even I don't!

Mine doesn't go over 3k rpms towing and I'm sure that isn't where the peak is at. I bet it's sub300 towing.

 

[Charles]

See this is what has me stumped. The new trucks have 400hp at the crank, lets say they loose 60hp when it finally hits the ground. It still has 340hp to the wheels. They're rated to tow 20k In a DRW platform and they're holding together?? Does the engine limit HP when it feels a load?


Sent from my iPhone using
TapTalk
2000 Black DRW F-350
2012 pearl white Focus

Those trucks are only making 40 or 50hp more than what I suggested to be the max for a 7.3 vintage superduty, yet they have coolers on top of coolers on top of coolers. Hell, the diffs come with finned cooling cover plates. Fuel coolers, big trans coolers, hell they don't even offer the ZF6 anymore because..... yep.... it couldn't hang....

I'm sure that loaded to around 30,000lbs and running down the interstate for a few hours the driveline on those is getting a little upset even still.

 

[Jomax]

Makes sense now, guess I'll stick with stage 1's or even stock injectors..


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TapTalk
2000 Black DRW F-350
2012 pearl white Focus

 

[Hotrodtractor]

Push the tow/haul button and it changes the way it drives. Who hammers the pedal to pull a trailer full of something? Even I don't!

Mine doesn't go over 3k rpms towing and I'm sure that isn't where the peak is at. I bet it's sub300 towing.

I do. LOL Hammer down with a 36' gooseneck with a truck or two on the trailer.... I enter interstates at traffic speed, I never ever loose speed going uphill - sometimes I even accellerate going uphill because of a tuning hiccup that it actually demands more fuel than the pump can deliver at low engine speeds - so you hammer it, it downshifts, the engine turns faster, and you accelerate uphill. Ask Matt_P, Mink, or anyone else that was in the HRT Roadside Rescue tow truck when they got rescued from their return trip home from BDP's Dyno event.

 

[Buffalo444]

Those trucks are only making 40 or 50hp more than what I suggested to be the max for a 7.3 vintage superduty, yet they have coolers on top of coolers on top of coolers. Hell, the diffs come with finned cooling cover plates. Fuel coolers, big trans coolers, hell they don't even offer the ZF6 anymore because..... yep.... it couldn't hang....

I'm sure that loaded to around 30,000lbs and running down the interstate for a few hours the driveline on those is getting a little upset even still.

Really, we don't need much horsepower for continuous towing. It only takes 250 hp to move 80k lbs at 55mph down the highway, and 400 hp to move it at 75. Say you maintain 65 mph, you're only looking at ~325-350 horsepower needed. To move 80k lbs. No way the driveline or brakes could handle that for a sustained period of time, but the horsepower would be there. Really, as soon as you hit the 7.3 SD, the horsepower hit the point where you didn't NEED more. After that you just got acceleration bonuses.