Featured Technical Transmission horsepower losses

Had 2 f100s
Both with FEs. The one with the c6 got around 4 less mpg than the one with the manual

 

Man this thread intrigues me!
I don’t doubt gaining a couple thousand RPM by switching transmissions.
An interesting experiment would be to activate the AC idle solenoid with the AC unhooked and see what the RPM gain is. I believe an AC unit pulls 2 to 5 hp. If the RPM increases a like amount then we could reasonably ***ume the Auto draws 2 to 5 HP at idle.
Dan

 

Are lock up converters available for older transmissions?
Dan

 

I would think that the information that @justp***inthru posted were either done at a specific rpm level or one that reflected the worst condition they could find at whatever rpm that it occurred. In either case, it simply reflects the fact that each transmission will remove that many HP at some point while driving.......but not as Jim says ......at all rpms. Still its a way to get an idea of actual hp loss for comparison.

It would be nice if we knew what HP loss occurred with a manual transmission, as while they are more efficient, it does take some hp to spin a heavy flywheel and clutch that most cars/trucks had.


Something else to consider would be that newer "overdrive" automatic transmissions "may" out perform the older manual transmissions because most manuals were 3 speeds and 4 speeds but had 1 to 1 ratios in high gear. The addition of an overdrive in the automatics "might" give them an edge over the older 3-4 speeds both in acceleration and mileage. There probably is no clear winner here since different engines would get different results in the Hot Rod world.

BUT...........then the 5 and even 6 speed manual transmissions evolved into being and now the game changes yet again.

And then the automatics evolve and now we have 10 speeds or whatever...........

I think the general thing is still that a manual transmission uses less hp than a comparable automatic, and an overdrive in either transmission is beneficial both to acceleration and mileage. (The OD helps acceleration because it allows a lower rear gear to be used)

 

I saw a car at a show this summer with a stock flathead, automatic and AC. I roughly calculated that he had maybe -10 HP at the rear wheels.

 

Hahaha, that´s a good one^ he probably had two buddies push him to the show

 

Neighbor put a c6 behind a flathead.
Lost so much hp it only moved backwards

 

Yes, and it has a AWD transfer case hanging off of the tail.

 

If you stay on the starter, it's a hybrid!

 

Older than what?

1979--1984 GM offered the TH350C. It had a lock up converter.

Other than that, no, but adapters are made to put newer transmissions on older engines.

 

Thanks, I know Chrysler 904s had lock up TCs in that era also, didn’t know if there would be a way to make a lock up TC work with out the corresponding transmission.
Dan

 

We need someone to build a multiple bolt pattern bell housing hooked to a large electric motor so each transmission could be run on a dyno with nothing but a drive shaft. Run each one through its gears up to a set rpm or speed, then run just the electric motor. It would be the only fair and accurate test of drag each one has. It would be an interesting test.

 

Powerglide and T400 are available with lock up converter, used in drag racing .

 

Back when I was kickin' **** and takin' names at the weekend quarter mile, the only legitimate "testing" was a freshly printed time slip. Everything else was ********.
I do recall that it was commonly believed that shedding 100 pounds from a vehicle could yield about a 10th of a second off the time. I forget how many car lengths a 10th was worth at 100mph through the lights. Those manuals were easily 100 pounds lighter than those autos. So even if 2 cars had identical HP, the lighter one had the edge.

 

The valve body played a part in 904s lock up circuit. The trans. case is machined for each specific valve body.

 

Don’t think Ive ever cruised in an old ride and said “dang this transmission sure is eating a lot of hp”

 

You might need to in order to pull a hill.

 

I'm sure this is true of you and many others. There are also people who want to find every little bit of giddyup possible.
Each to their own.

 

As far as being quicker. Back in my street racing days I could beat 383 4 speed road runners by 3 lengths in a quarter while 383 Automatic Roadrunners would normally beat me by three lengths. That was identical cars except for transmissions. There are more things involved than just power loss to the rear axle.

I don't argue the point that there is more power loss between crankshaft flange and front driveshaft yoke with and automatic than a manual though. Also that there is more power drain with the bigger heavier automatics rather than the smaller simpler ones.

 

Drag racing gravitated toward automatic transmissions. Probably not because they were slower.

 

An automatic would gain most times in racing. It took a lot of skill and coordination to speed shift a standard transmission fast & without miss shifts

 

No matter how fast you shift a standard four speed you always have the time you’re not applying power between shifts. With an automatic you don’t have that, you’re applying power the entire p***. I’ve seen enough side by side videos of automatic vs manual and you can see the manual car drop back at every gear change. Back in the early 60s the SS Mopars were faster with automatics than manual transmissions. However I don’t think it was that way with the Thunderbolts, quite a few of them were converted to four speeds they had a Lincoln automatic…
Now the C4, turbo 350 and the 904 are used behind big inch big blocks because of their efficiency. But you will pay big money for a C4 that can handle a 1000 hp.

 

The day before this thread started I fired up my old Buick and drove her out of the weeds. A 53 nailhead with a DynaFlow. Out on the road tromped on it and thought, man, wonder where all my horsepower is going?

 

Don't confuse hp loss with performance in an automatic trans. What I mean is the torque converter multiplies torque so you gain back some percentage (or more) of the loss of the pump and rotating parts. Also don't forget a manual trans also has some loss with rotating parts and flinging fluid around. Both trans have bearing friction. A high stall converter allows an engine to reach max torque transfer for longer period than a slipping clutch generating heat.

Overall I think it's easy to understand a larger automatic has more internal loss. But manual trans also has some loss, less than an automatic. But that loss isn't a direct proportion to performance. Likely the biggest effect of automatic vs manual is going to be found in steady state cruising conditions.

 

I think for a lot of us, the reality is, "How many more years will this bum knee push this pedal in?"

 

Ronnie Sox might disagree. https://www.facebook.com/watch/?v=1083045633636114




.....

 

For me it’s drivability and the auto’s get driven more than the manuals. My wife won’t/can’t do 3 on the tree so if we take “old oily” I get to do all the driving. I have an equal mix of manuals and autos with the autos mostly C4’s and 1 700r4. The manuals are ford 2.77 and T5 and T170 and a few I have no idea what they are 4 speeds. Of the autos the only one thats confusing is the green dot. With the manuals the column shift is always difficult for just about anybody who has not driven one daily for a few years.

 

The car makers must have thoroughly tested their transmissions, producing graphs of power consumption vs. rpm vs. load. Strange that this information never seems to have leaked out.

 

Regarding any change in idle with a C4 transmission to T5 transmission swap behind a 351W, my idle only went up about 200 RPM with my swap. Stock converter on the C4, very healthy lopey engine (about 12 in/Hg vacuum at idle.

 

You are correct. This is the reason the Lenco was developed. Right?