I discovered last weekend the rebuilt 700-R4 in my Brougham acts differently than a stock transmission. When I drive around with the gears-selector in Drive, the tranny downshifts agressively and at higher speeds than when I'm in Overdrive. For example, in Overdrive, I'll be coasting up to a stoplight with my foot on the break. I'll barely feel the tranny downshift into first, if even at all, usually around 10-12 mph. But when I'm in Drive, coasting to a stop, I can feel the tranny downshift into first at 18-20 mph. I can sure hear it too. It downshifts similarily for other gears.

Furthermore, even though it shifts like it has a shiftkit in Overdrive, it shifts ever slightly harder in Drive. When it was rebuilt, I had a larger input drum, better servo, and a stronger 3-4 clutchpack put in. Do you guys think this has anything to do with it?

These things have overdrive?

Very interesting.
Maybe the present transmission in my 95 FWB is uniquer (!), but the CPT Stage II and high-stall converter really did nothing to make the car seem to shift harder EXCEPT when shifting into direct.
When it does, there's a very noticeable thump unless I'm listening closely and lift my foot.
Otherwise, it downshifts softly, and upshifts smoothly - not like the old 2 speed Powerglides or Buick Dynaflows, but more noticeable than the original trans.
I have now gotten used to it and listen closely for the upshift and back off a bit, just like I did with my old Plymouth with the 383 4-barrel.
And just like that old Mopar, if I stick my foot in it, the motor winds up closer to the torque peak, thanks to the new converter and the old gal picks up her skirts , chirps the rears at the 1-2 upshift and makes ricers think twice at the next stoplight.
I wonder if the converter might make the rebuilt trans seem like it's too harsh and a high-slip converter might make some difference.

The owner of the shop and I both agreed on having a very firmly-shifting transmission to get the most life out of it that I possibly could. The stall is 1600 rpm I learned, so I'm only 400 rpm from peak torque when I hit the gas. Still, I didn't know a tranny could act differently just by changing the gear selector.

Sounds like you got a good transmission man. No B.S., just the facts. Hold on to that rare bird!
My converter is looser than the speed you mentioned, with - I think - rating at about 2,200 rpm. Shane, of CPT, said the effect is to make the car seem 1,000 lbs. lighter and that's a great description of how she feels with that Stage !!.
What I especially like about that converter is the lack of creep at stoplights. In addition, my wife loves that feature (when I let her get behind the steering wheel).
Could you simply be "spoiled" by the smoothness of your previous set up and now the trans simply seems harsh?

I sure would like to toss in a looser converter in mine. I really feel that the converter is what is holding these big boats back. I put in a 3.0L V6 converter in a 4.0L Aerostar van once. Loved the way it drove. The only issue is say on a steep hill it stalled a lot more. But still was fine. It made you feel like it is slipping (will roll backwards a lot more too on a hill)

Maybe a S10 converter one of these days...

Yeah, you lucky guys with your LT1's could use a little higher stall speed to really use your power. Us LO5 guys have such low peak torque RPM's a different converter wouldn't do near as much for us as it would for you, me especially, I think when I advanced my timing 12* it moved the powerband even lower.

If the powerband is low, capitolize on it. Don't go excessive on gearing (then again, they did put the 3.73 in for the V4P cars).

Think of things to boost higher rpm power would be 1.6 rockers (they bump up timing a couple degrees), you can retard the cam will move the rpm range up (worn timing chains do this for you), increasing velocity helps the small cam seem larger to the engine.

Probably the #1 best investment I would recommend on a L05 is ditch the heads and get some Vortec heads. Bucks down? 1.6 rockers. But you might need springs (good chance of it) to keep from coil bind. So you might end up spending the same $$. But there is more work to put on the Vortec heads. So if you don't do it yourself, that is a $$ too.

One of these days I need to get me a L05 to see what makes it tick!

The heads are the definate weak-point of any LO5 but can be made to make brutal torque with the right cam due to the swirl port nature. Some Vortec heads would be nice but due to Midwest winters, I'd need some AFR or Trickflow heads for cold-weather drivability. Vortecs are a great bang for the buck, but I can't wait 20 minutes in the winter for it to warm up.

If your car isn't in closed loop and warmed up making heat in 3.5min, there are PROBLEMS, fix them. Iron heads vs Aluminum won't make a difference here. Iron are probably better, iron conducts heat better than aluminum.

3.5 min seems to be a pretty common time in GM land where the MUST be in closed loop. But you should be pretty much fairly warm by this point.

I was under the impression Vortecs didn't have the exhaust crossover through the middle of the manifold, thus the poor cold-weather application.

You are correct, they don't. Personally, if you are in a warm enough climate to not need it then don't worry, else I would fix a water crossover to the intake to warm it and plumb it with hot coolant. Then you can rig a shutoff in the summer (Tom's #1 tip for my Turbo Trans AM) so you can cool the intake down to gain a little power (maybe....) And if you do it right, you can pump cold or ice water through it when you are running at the track that day....

I was under the impression Vortecs didn't have the exhaust crossover through the middle of the manifold, thus the poor cold-weather application.