I don't get the "percentage of power" thing. Don't make sense to me. You're not changing what parts weigh, (centrifugal force) or the fluid, it would seem it takes "x" quantity of power to run the trans. No matter what size engine is in front of it. More HP available, less percentage of the whole.

I asked what I did in the most general of terms, I'd think one 727 would eat up the same #of HP as the next, unless that "next" one was modified vs stock (rollerized, whatever)
Or one 904 vs another, or one 500, or one a833od vs another one just like it, etc etc.


But more specifically in my exact case whatever trans I run on this project will be run by a built up /6. I don't see something like that "8hp-whatever" coming close to a possibility.
If I decide the a500 is my trans of choice I'm gonna have to find a /6 to small block trans adapter as it is. The truck currently has it's original and working 727 in it. The only thing I have to do to that is find the leak(not the pan or the input or output shaft seal) and add a mild shift kit so I can stop the converter drain back situation it has. And drive the snot out of it from there.
But I just got an 833od with flywheel, bell housing, pedals, linkage and everything I'd need to swap that in except for a new, fresh clutch which I believe I may have in the attic. And I have an a500 here too, that worked when pulled, that I'd rebuild before I use it just because of age and past maintenance being an unknown.
But being a 500 is '904 based" it seems a downgrade vs a 727 in terms of durability. I don't have a 518 at present. I'd like to run something I have. If it's the 500 is definitely have to do some beefing up just for my own piece of mind.

If I'm gonna make a change from the 727 it's gonna be a change to the least power sucking option I have available and on hand.

727 with locking TC?
Rare as hens teeth!

So, everyone on Moparts contribute $20 and buy a “transmission dynomometer” to test efficiency and power consumption?

https://powertestdyno.com/product/transmission-service-450e-series/

Or maybe give a “shout out” to trans shops that already own and operate units?

So, everyone on Moparts contribute $20 and buy a “transmission dynomometer” to test efficiency and power consumption?

https://powertestdyno.com/product/transmission-service-450e-series/

Or maybe give a “shout out” to trans shops that already own and operate units?

The percentage is because you are acceleration a load. Think it through. It takes more power (a greater number because the percentage stays the same) so it’s not a fixed number but a fixed percentage. (a powerglide is about 19-19.5% and a TF is about 21%). That means that it robs the same PERCENTAGE of power no matter what. 21% of 500 hp is 105 hp and 21% of 1000 hp is 210 hp.

So the percentage stays the same but the actual power consumption number goes up because you are dealing with a percentage of how much hp it takes to drive a gear box.

Look at NHRA Pro Stock and Mountain Motor Pro Stock. One is 500 CID and about 1500ish hp. The other can be some really big CID, BUT the power doesn’t go up as a percentage of CID because friction losses are also a percentage.

So let’s say you are looking at a 500 CID engine and comparing it to a 700 CID engine. At 1500 hp, you get 3 HP/CID. And the 700 CID engine makes 1750 hp which is 2.5 HP/CID. Because the friction losses are a percentage of total hp, the bigger engine makes more hp but is less efficient (2.5 HP/CID rather than 3.0 HP/CID).

If you made the bigger engine even bigger, the flywheel hp would (should) go up but the HP/CID would go down.

I would have figured theres a westech/Steve Brule type of person somewhere out there that has already run such tests and that there would be a published list out there "somewhere" that already exists with such info.

In the 80s when I went to a local community college in their automotive program they had a trans test machine, that could be used to test a transmission, usually after a rebuild. It had lotsa adapters for bellhousings and tq converters, I only ever saw it actually get used once in the time I was there, it had a 4 banger (1.6?) Toyota engine to power it, that I remember hearing was donated by a local wrecking yard to power it. It had a bank of pressure gauges that could monitor pressure at any of the pipe plug test ports but I don't think there was any "dyno" function on it to test power used by a given transmission

That’s not breaking the trans from power.

Most likely a leak, low fluid, misadjusted throttle pressure, lack of maintenance (misadjusted band/s), etc.

/6 wont “break” a 500.