If you are at full throttle on an engines torque peak, say 270ft-lbs than that would be the most torque the tranny takes. Why is it that when loaded with a trailer, that it puts that much more strain on the tranny? Almost like how putting bigger tires on a truck can break the axle shafts, why? It's still getting 270 ft lbs of torque. Can anyone explain?


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

I cant answer the question on towing sorry.

I believe that the answer for why larger wheels/tires can be damaging has to do with coriolis effect, (earth spins at next to nothing at the poles, and approximately 900 knots at the equator)if we increased the land mass at the equator we would increase the rotational speed. not the number of rotations. This would have a dramatic effect on the earths magnetic pull.

Effectively it is producing @270bhp for a given rotation, and when you add larger wheels/tire combo, you are increasing the amount of grip per rotation, grip is friction in this equation. The increased friction adds stress to axles,

I guess maybe thats not a good example, I hope it helps, I will try and put it in better terms and edit this shorty..

sorry.
Drew.

 

ok...i'll start with the bigger tires cause its the easiest...the closest thing that i can think of is this. Go in the garage and get a six inch long ratchet,,,now go try to break a wheel stud with it,,,,its not going to happen....now go take a four foot long breaker bar and try to break a wheel stud...it won't take much. granted your motor puts out only 270 ft-lbs of torque...but its being multiplied by a longer lever, your tire....its all a matter of physics. now for the towing thing...your truck puts uses full torque only when starting out or accelerating hard generally. Say you have 300 lbs of torque. You may use that for a couple of seconds when accelerating but once you get up to cruising speed your truck really only needs 100 lbs to maintain speed. Remember things in motion tend to stay in motion. once its moving you only need to overcome friction of the road and air. (just guessin on real numbers) anyhow, the heavier the truck the more power needed to keep it moving. This is due to more friction with the road and air. Now your clutch or bearings or anyother parts are normaly only subject to minimal amounts of torque for any extended period of time. Now if your towing your motors running a little harder to overcome friction, and your clutches, tires, driveline and fluids are going to be subject to more power for extended periods. I hope this made sense, if not let me know and i'll try a different approach.


Ryan

 

As Ryan said your using more power to turn the gears. If you have seen in most manuals you have your input shaft running halfway through the tranny with different size gears. Your have two other shafts on either side also lined with different size gears. When towing your using more power to turn the gears so stress is added to the gear surface. This extra force is also carried through the bearing and ultimately through the housing of the transmission. During normal driving your not using extra force to turn your gears so it is instead transferred through the rest of the driveline and to the wheels. Hope this helps.

 

This is an interesting subject---I will conjecture abit---when the truck is in any gear with the ratio being less than 1:1---it would seem to create somewhat of a mutiplier effect--i.e.if the ratio is 4:1--engine to tires----and if the max torque is say 300 ft.lbs--is it correct to say that you might have 1200 at the rear wheels ignoring friction losses!!!To postulate even further---in all the mags the rock climbing guys are always busting axles when they are barely moving---in a very low gear , O.K.----you NEVER hear of anybody breaking something running down the road at 70 mph , i.e. , the ratio being 1:1 or greater if they have an overdrive---I hope I'm not full of hockey about this---Where is old Dennis when you need him!!!fd :-X11

 

So your saying the extra stress is because the power is for a longer period of time. OK, that would wear out the tranny faster, but why would it totally break a tranny. Like if I loaded my F-150 up with a 5,000 lbs trailer, the mazda would probably bust. Why does it bust? Wouldn't it need MORE stress on it(more engine torque), not a longer amount of stress for it to just eat itself? The max torque being applied to the tranny from the engine is the same whether it is loaded or not loaded. It will take more torque to keep you moving but you are still only putting 270 there at the maximum point. I don't understand why a tranny would bust from towing a lot of weight if the engine power is the same. I can see that there is a more stress for a longer period of time, but that stress still doesn't exceed what the stress would be in 1st year at max torque. So if it can handle the torque in 1st year at max, why can't it with a trailer on it?

I can see how the tire thing can relate, more stress over the life of the truck's axles but where does the extra torque come from to just break one? If the torque applied from the engine increased, i could see why. I dont follow the leverage thing that ryan talked about. If you have a 6" ratchet vs a 4' bar then yeah you can put more torque on it, but you're applying the extra torque. How are the tires exurting more torque to the axles?


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

>How are the tires exurting more torque to the axles?

The tires are not exerting torque to the axles. It takes more torque from the axle to turn a large tire than a small one. That's why when you go to oversize tires, you need to regear the axles to a higher numerical ratio to get the same power to the road.

An engine will only make it's peak power while under load. Think of it this way: turn a bicycle over and turn the pedals with your hands. Pretty easy, aye? That's like your truck running around empty. Now have someone grab hold of the tire. You have to work hard to turn the pedals now. That's like your truck loaded going uphill or pulling a heavy trailer. It puts a lot more stress on the drivetrain components. The added strain increases the friction on all the moving parts and builds up heat.

The rockcrawler's break stuff because they are geared so low that they can make too much torque if they don't apply the power slowly and smoothly. Think of someone holding a cardboard paper towel tube in their hand just tightly enough that you can slowly turn the other end. Now suddenly turn it hard and fast and it will twist or tear the tube.

 

Ok...if we combine everything we've said here we get a pretty good awnser. As for the engine putting out peak power under load, thats exactly right...towing is kinda like doing five grand clutch drops all day....you just are not going to do it for long before breaking something with a mazda. and the same thing applies to the axle question....your stock geared tires require more power to turn,,therefor your engine produces power closer to that peak number and puts more torque to your axles. One other side note on the tires, a larger tire requires more power to begin turning it, therefor putting more stress on axles during acceleration, it comes back to newtons law of things in motion tend to stay in motion until acted on by another exterior force, in this case power from the axle. The heavier the tire,,the more stress it exerts back on the axle. yes 35" mud terrains exert alot more stess than 235/75 inch firestones on your axles. The 50 pounds or so more they weigh doensn't seem like alot....but it is.

Ryan

 

But if the truck is empty, and you floor it in 1st gear, you are putting as much torque as possible from the engine onto the drivetrain (except for low range). If you are towing a trailer you will need to use more torque to keep the truck moving, but you still don't exceed the max that you get from 1st gear. The only thing you are doing is asking for more toque to be applied over a longer period of time. You're not asking for more than the max amount of torque. I don't know this is a pretty difficult concept i guess.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

But if the truck is empty, and you floor it in 1st gear, you are NOT putting as much torque as possible from the engine to the drivetrain. You are only applying as much torque as it takes to move an empty truck.

Remember power is measured by the ammount of work done. It's less work to move an empty truck than one loaded and pulling a trailer.

Here's another analogy:

A weight lifter can bench press 400 pounds. So let's just say he is exerting 400# of power to move the weights. The amount of work he is doing is measured by the weight he is moving. The exertion required to move the weight increase the weightlifter's pulse and respiration, and he breaks out in a sweat.

Now he removes all the weights from the bar, and starts pressing the empty bar, which weighs, say 20#. The exertion required to move the weight hardly has any effect on the weightlifter's pulse and respiration, and he doesn't break a sweat.

So, because the weightlifter is capable of pressing 400#, does that mean he is exerting the same amount of power to move the empty 20# bar? If his 10 year old sister can press the empty bar, does that mean their strength is equal?

 

I don't know if I can see the connection with the weightlifting thing. If you can lift 400 lbs, than yes when you lift a light bar you're not using that 400lbs. However, if you were like an engine you could exert that 400lbs of strength but you'll push that light bar up in no time. See what i'm saying?


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

I see what you're saying. Yes, you'll push the light bar up in no time and you can do it rapidly and repetitivly without getting too tired. But does it take the same amount of effort that it does to lift 400 pounds?

Another example:

You have two identical gasoline powered electric generators. The engines are rated at 100 hp max output. Their speed is governed at 3600 rpm.

Generator A has no load on it except for the power it takes to spin the unloaded generator rotor.

Generator B has a 2000 watt load on it. The engine lugs down and works hard, but the governor keeps it running at 3600 rpm. It's load is the weight of the rotor, plus the electromagnetic drag from producing 2000 watts of electricity.

Which engine is producing more power to do it's work at 3600 rpm, generator A or or generator B?

Hint: After 4 hours, generator B's engine runs out of fuel. Generator A's engine continues to run another 2 hours before it runs out of fuel. Why? They were running at the same speed, shouldn't they be both making the same amount of power and consume the same amount of fuel?

 

Yeah I get where your going now. Its back to the thing where unloaded say you need 100 ft-lbs of torque to keep it the truck moving vs 200ft-lbs when towing. So there is more stress over a longer period of time. But I just don't this part. Does the tranny break from having that much stress for that long? A constant 200ft-lbs is a lot more stress than 100 ft-lbs. The thing I dont get is that why can it take 270 ft-lbs during aceleration but can't take 200 ft-lbs for a few hours? You'd think that that quick aceleration burst in 1st gear would be to a lot more force than a steady 200 ft-lbs while driving.

Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

even a quick 1st gear drop isn't putting out as much power as a loaded trailer 1st gear drop. try this out....you take an impact gun thats rated for 500 ft-lbs. you jack your tire up off the ground and put the impact gun on the wheel stud, you pull the trigger and the gun takes off, the tire going with it, the guns rated for 500 ft-lbs and a wheel stud will break long before 500 ft-lbs, but yet the wheel stud hasn't broke. Now you put the tire down on the ground, and do the same thing, the guns not going to take off right away,,its going to bog down and rap on the stud for a couple seconds, then the studs going to break. Same thing as a tranny, think of your tranny as a wheel stud and your motor as an impact gun.


Ryan

 

This topic is confusing. Just to clarify i didn't mean a 1st gear launch empty vs with a trailer. I think this is a lost cause hahah. Whenever i've used an impact gun it won't spin the tire if it is in the air.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!