Why would the engine apply more torque, just because you change gears?

The engine provides enough torque to maintain the speed (overcome the air resistance), this value is a constant at a constant velocity.

Some basic engineering that applies here:

A vehicle at moving in the same direction at the same speed has a constant velocity. This is defined by basic engineering as a "Static" situation. For a static situation, the summation of all forces on an object is zero.

A= force of air resistance on the vehicle

E=Force of motor = force of the truck pushing back on the air.

A-E=0 (subtract because the forces are in opposite directions)

Also consider conservation of energy. If you move the same object throug a medium (air in this case) at the same velocity, the force pushing the object is basically the same as the air pushing back on the object. There are other losses within the system starting within the engine itself (thermal inefficiencies, not burning all the fuel, some friction loss etc), in the transmission most of our loss is through friction. If you lost any energy mechanically, that would mean parts are flying off :-) Or there is more energy being transferred to the vehicle motion=acceleration=not a constant velocity.

What you guys are trying to tell me is that the loss through the transmission changes when we change gears. This does not make sense.

 

Hey there,
The best overdrive- Put an NV4500 in your ford. That's what I'm doing. They shift like a champ and you can do it for under $1500 if you're resourceful.

 

If there isn't any more power loss when in OD than in direct, then why does the transmission temp go up, when in OD? The extra heat is created by applying more torque, to do the same amount of work. Apparently, Gtex still hasn't tried the demonstation that I suggested to see what I'm talking about. Just because you have a degree in physics, doesn't neccessarily mean you can't be wrong. I had a cousin that graduated college when he was 19 years old, and was working on his doctorate, when he died of Legionares disease. He had all the book learing in the world, but he didn't have a lick of common sense. Formulas are handy to figure out what might happen when you do something, but untill yuo've actually applied your theory, you can't possibly know for sure, there's just too many variables in the real world to have a formula to have a 100% accuracy rate 100% of the time. Even when I was a kid, I knew that "bicycle chain" demonstation told me that it took more torque to do the same work in a higher gear ratio.

 

Ya know, I don't have a degree in Physics, nor have I tried spinning the input shaft of a transmission, but the FE engines still seem to me like they'd have enough torque for an OD application. Call me a dumb redneck if you like, I'd do it if I had the means.

 

I think I see where I'm failing here.


I'm thinking about work and you guys are thinking about torque.

These are both physically defined parameters.

Another good system to look at is a chain hoist. I can lift 2 tons by only applying 100lbs of force. But, to move the 2 tons one foot, I'll have to pull the chain 40ft. So, yes the amount of force I have to exert at one time is 100 lbs. But I've still moved the equivalent 2 tons one foot.

So looking at this system, It looks like more force would be required at the motor in a higher gear. But, it will perform the same work through less distance. In this case, fewer rotations. In any case, it is performing the same amount of work. So long as your motor is producing enough torque at that lower RPM, I don't see how this could be a concern. Consider how much more torque is applied under hard acceleration. This is much larger than that required to maintain highway speeds.

As for the transmission heat, that should be easily explained by faster rotating parts within the transmission.


I'm probably doing a poor job of explaining this. And, I'm not trying to sound arrogant. Just trying to keep my mind off other things right now. Plus, it can't hurt to think over some of the stuff I forgot from school.

One thing I do know, I love that feeling on the highway when some Civic with a fart pipe comes along side me. I'm humming at 1800 RPM at 80 MPH. I drop to 5th, he hears it but I'm still purring. I drop to fourth , they take notice cause shes breathing a bit now. I drop to 3rd and they are usually looking at tail lights :-) then, back to 6th, and 30 MPG :-)

For those of you that are anti-OD, why are most of the newer most desireable cars offering a 6 speed. It's just a gimmick?

 

if you've followedford trucs they also have been coming out with the 6 speed for heavy duty trucks and getting away from the 5 speed, i see your point gtex, i actually understod what you osted there, and i think it makes sense.

 

I think for basically stock engines there is no ignoring the benefit of an overdrive tranny; the engine is designed for maximum off-idle torque so it is very happy churning along at low RPMs. However, if your engine mods have shifted the powerband significantly from idle the engine efficiency at low RPMs may suffer enough to offset any gains from the overdrive (I'm thinking of the 427 Mustang here).

For those looking for AODs for the FE, these guys http://www.c6-c4.com/ have an adapter kit for $795 that includes the starter and flexplate; I haven't tried one myself but I'm thinking about it. I have no idea of the price of a decent rebuilt AOD but it's clear the whole swap won't be very cheap. On the plus side, the Ford E40D is based on the C6 (many parts interchange) so I would expect it to be pretty tough; performance clutches etc are available as well. Now, I just wish Gtex would quit braggin' on that durn chebby! :-)

 

You're forgetting one part of the equation Gtex, your theory supposes that , the extra force, is only used in one particular instance. But a moving vehicle encounters many different situations, requiring the motor to use more or less force to keep the same speed, depending on the circumstances, this repeated application of more force, is where the the majority of the heat buildup comes from, not just from faster spinning parts. Like I said before, those physics formulas work only in a fixed situation, which in the real world doesn't happen, the variables are constantly changing. I'm not against OD transmissions, they do serve a purpose to a point, but I'd rather see the US auto makers comeout with lower geared transmissions and higher geared rears to accomplish the same goal. The transmissions and driveline would last far longer this way. The 6 speed that fordman428 is talking about more than likely doesn't have 2 od gears in it, the extra gear is most likely a lower first.

 

I don't know how much torque a 350 is pushing, but your comparing apples to oranges when you say Vettes and trucks. No insult implied.

The 390 pushes 425 lb/ft torque. Now, if you were to put dual superchargers and fuel inject a 390, WOW! I am sure someone on this site could figure that out. Someone here has desktop Dyno that could figure the specs.

 

*** Hey there, The best overdrive- Put an NV4500 in your ford. That's what I'm doing. They shift like a champ and you can do it for under $1500 if you're resourceful.***

averagef250 -- When you start this swap...Please! post a thread...I would love to see how it all turns out.


I like what averagef250 had to say. The (dodge not chevy) NV4500 is the best replacement trans we could modify our trucks with. The have a great super low first and are really bullit-proof for a Ford 1/2 ton 4x4.

However, with that said...I also like the AOD auto trans too. If they are modified in the right places can easily handle 700+ hp. Plus that would keep it true Oval FORD.

This has been a great thread!

 

I did not like the granny gear 4-speed my truck had so I installed a BW T-10 and 3.25 rear gears with my 390. Then I married and needed to be able to tow and back up a 5-8000 lb horse trailer- often. So I added a 3 speed behind the T10 and created a 12 speed. The basic setup is still in the truck altho the T10 was replaced by a TC Toploader(pass. car HD) and the original 3 speed is now a HD Ford RAT series 3 speed. The only drawback is the care needed when accelerating in a low gear in the 4 speed. The second trans sees the engine torque multiplied by the first trans gear ratio. My 428 makes at least 450 lb ftX2.2 in 1st gear=990 lb ft of torque going into the 3 speed!! So I am careful and use synthetic fluids in both trannys.
I now have 2.75 rear gear and am able to crawl or fly down the freeway!!

 

I've seen heavy trucks with setups like yours but never in a pickup. must be fun trying to remember what gear you're in when the wife starts talkin!

 

She actually wanted me to do it!!! Like I mentioned she wanted to be able to tow a big horse trailer without fighting the low speed manuevers. I'm fortunate she likes the old truck and lets me tinker with it. It is interesting to see the expression when you shift backing up and continue going backwards!!

 

I bet it was fun trying to get it all set up and working. How long did it take you to "learn" to drive it? Do you have any pictures of it?

Bobby

 

It did take some time to get working properly-about5-6 years of occasional tinkering. I built two custom crossmembers to hold the front and rear of the 3-spd. I ended up with a mount for the mounts on the front and a regular trans mount at the rear. The biggest process was lining the trans up so there isn't any driveline vibrations-that took most of the tinkering time.

I don't have any pic's to show my handiwork yet, but I will get some posted when I do. It really wasn't hard to get used to driving it, since most of the time I start in 3rd with the 4sp and then shift the 3sp normally. I unhooked reverse in the 4sp to avoid turning the 3sp backwards. It only gets tricky when towing since more gears are needed to move. I have got confused a time or two!!!