any way to get a little less power loss out of my c4?

i heard the c4 transmission eats a good amount of power for it's size, is there anything i can do to decrease my parasitic power loss?

 

Build your engine to make more power.Light weight trans components,low friction bearings.Paul S will know for sure what you can do.I am just throwing out obvious things.my understanding is they eat 40 to 50 horse just to make em function...

 

They are good for 18-20% loss.
Pretty standard stuff for an auto tranny.
The C6 is the one that eats huge amounts of power.

Figure what you have for flywheel power, then remove 20% and you have a good idea.
Most manual trannys rate 15% loss.

The T56 and aluminum driveshaft is said to be about 12% loss.

The problem with light tranny parts is that it can reduce torque multiplication, so it is somewhat a balancing act with a smaller engine. If you have a 460, then it will make so much torque, it doesn't much matter. But it will also be more likely to break light parts. Make sense.

I guess what I am saying is that a C4 is not a power hog. Put an aluminum shaft on it and you'll gain a bit.

 

I know this isn't transmission related, but if your just trying to get a bit more "scoot" then change the rear gears even slightly will help.

 

Yep... and I'll go along those lines too (away from tranny) and remind that a portion of that 18-20% parasitic loss is driveshaft, differential, and the weight of the wheel/tire combo.

If you can trim the weight of your rims and tires, you cut down parasitic losses. You can also use lighter axle components, which are less risky than light tranny parts, and don't cut down on torque multiplication like a lightweight flywheel/flexplate (for example).

Gun drilled and scalloped axles cost no more than 'trick' tranny internals I would think. And they can be ordered up straight from a shop like Summit.
Going to modern rear disc brakes can help too. Not refering to Versillies discs either, the old stuff is massively heavy.

Just some things to ponder.

 

Agreed once again

 

ya i dont think paracitic loss with in the transmission should be a main prority when there are so many other things that can be easily done to get your car moving along much better

i think the C$ still beats the AOD and C6 in these respects though

 

if its in good condition put in a shift kit and a adjustable vac modulator.

 

The losses in a C4 are very low to begin with but you can reduce the losses.
1. convert to needle thrust bearings instead of washers.
2. Use a "high efficiency" converter - not recommended for high output engines because they have a lower stall speed than stock and you will get better performance with higher stall speeds.
3. Lighten the rotating parts. This can be done on street transmissions to a limited degree. Most of the heavy parts are for park abd governor so you can only lighten a street C4 by about 2-3 pounds without affecting its strength.
Modifying the valve body and/or modulator will not make your transmission lighter but it will decrease the amount of "overlap" between gears and there will be a perceived increase in performance.

If you want to "feel" more performance then use a TransGo 40-2 reprogramming kit to get rid of the overlap in the shifts, lower your rear gear ratio to 3.5 - 3.75 to 1.
(this will decrease your mileage slightly) For more "performance" install a 2400 rpm stall converter. This will almost double the acceleration from a stop and give you better acceleration right up to redline - and beyond. You will also notice that fuel economy drops when you use it.
You can double this by adding an appropriate cam kit and by having the intake milled and fitted with a 2bbl (2100 or Holley 2300) carb that sits on the modified intake. (not through a 2 to 1 adapter. You will want to have the head milled and a three angle valve grind done while it is off for intake log machining. (the carb hole in the intake is milled into a slot to fit the Holley or Ford carb and an adapter is bolted to the intake that is designed to adapt a Rochester 2bbl to the Holley 2bbl.) there is a need to make or adapt throttle linkage and kick-down linkage for a street car.

 

I was curious about this

It did not make sense to me.... Think about it.

If a auto tranny was eating lots of HP, then it would get kinda hot?? The intercooler, and the pan/housing is the only "radiator". Hmmmm.....

A 3/8 line with a comparative trickle of fluid is not going to drop 22,380 watts of heat (30 HP).

My $0.02 worth
-Pat

 

30 FWHP losses would mean the engine in front of the C4 was generating 150 FWHP, or 120 RWHP. Not all that much power really.
To be fair, the tranny is not the only place that parasitic losses occur, but they are a large chunk of the equation. A percentage of loss happens in the rear, and the heat is dissapated there. Same with brakes, tires, driveshaft, etc...

The tranny cooler system has quite a bit to deal with.

A healthy street engine producing 400 FWHP is going to lose 80 FWHP between the flexplate and the rear wheels. At best, if a C4 drivetrain only loses 18%, that's still 72 FWHP.

A manual tranny drivetrain loses between 12% and 15%... And a manual tranny has no pump, cooler, heat sink to speak of, and it uses far less oil, which is prone to retain heat from it's extreme viscosity. It still works.

 

Typical losses in a modern drive train are only about 10%, with a torque converter it rises slightly over that. No C4 uses 30 HP. As speed increases and loads drop the converter becomes nearly 95% efficient. At low speeds and high loads the torque converter uses hp to double the torque output. When you need to acelerate that torque is exactly what you need. It is a good trade off in any vehicle.

 

I think you may have meant "transmission" instead of "drive train" in this statement...

It is proven fact that manual tranny drive trains lose about 15% and auto drive trains lose about 20%. More or less depending on exact configuration. These are just guidelines of course, a C4 drive train would lose far less than a C6 drive train, for example.

Make sense?:Handshake

 

It also depends on the conditions being measured as to the losses.
I was speaking of average drive train losses - not losses at full throttle under full load like chassis dynos measure. The average losses are near 10% for the complete DRIVE TRAIN.

 

Okay... I understand what you mean, but on a chassis dyno, power, load, and losses are all measured with the engine at full throttle while load and rpm increase. So to compare flywheel horsepower (measured full throttle as well) and rear wheel horsepower, you need to look at the big picture. You are looking at street driving and cruising. I am comparing measured numbers.
Going down the road, a C4 will drain very little power. An object in motion tends to stay in motion, helping counteract parasitic losses.
Heavy flywheels work under the same theory, gaining inertia to amplify engine torque with wieght in motion.