Automatic transmission - learning the ropes..?

[defiance]

Alright, I've got a project plan layed out for the engine and body work on my car, and it all looks good.  However, as I read it over, I figure there are going to be two weak spots in my charger - Suspension and tranny/rear end.  For reference, it's a '72 with a 440 that will be built to 496 stroker, mid-500's lift, 290's duration cam, Edelbrock Performer heads, 10.5/1 compression, tight quench, dual quad intake with 2 4-bbl throttle bodies (I'll have sleeves so that I can mod them anywhere from 450 to 750 cfm; I'm betting they'll be mid-500s when it's all said and done) modified for port injection; Should probably be around 550-600 hp to the crank, maybe a touch more than that in torque, I'm thinking. 

But anyway, I picked the tranny to edumicate myself on first

So I've been reading a good bit on transmissions over the past few days.  It's a 727 auto, and the first thing I noted is that everyone seems to really like 727's - it's apparently a beast of a tranny at heart.  So, I probably won't have to do anything to make it 'survive' that kind of horsepower... or at least, that's the impression I'm getting.  Is this right?

Next, there's a lot of discussion around manual valve bodies.  Keep in mind I know NOTHING- but I've skimmed through product descriptions on several, read quite a few posts, and I'm apparently just being dense - what do these actually do?  I get the impression they give the driver control over the shift points somehow?  If so, how is this usually executed, is it a button inside the car or something?  Finally, how does one install one of these, is it as simple as removing the pan, taking the old one out, putting the new one in, bolting back up the pan, filling with fluid, and you're done, or does the transmission have to come out for it?  Oh, wait - one more - Are there performance advantages besides the ability to control when the car shifts as well?

Finally, I'm planning on changing out my rear end (currently 2.76 or something like that) for a 3.73 9" ford - I can get one with discs on it for a few hundred right now, and I've got help with the necessary welding, so it's a bit hard for me to turn that down
With that in mind, should I consider an overdrive?  Now, fuel economy is in NO WAY a concern here - I'm just talking from a performance perspective.  Though, on the other hand, it would be nice to get the fuel mileage high enough that I could consider driving it to meets or shows if necessary...  but not a priority by any means.  The gear vendors site went into a big speel about keeping gears in tighter ranges, but wouldn't it have to work with the transmission more directly to be able to do this?  I had always through that the shifting portion of the transmission and the overdrive were always completely independent...?  Bottom line, though - it's $2500 for one - is there a major benefit I'd see from getting one?

[myk]

In regards to the manual valve bodies, there are full manual and semi-manual valve bodies.  The full manual valve bodies will require you to manually shift the transmission at all times, where the semi-manual valve bodies will allow you to shift at your discretion, but will shift on their own if needed...kinda' like what we do now, anyways-lol.

Either full or semi-manual valve bodies can be tailored for more firm shifts which will add to performance.  As far as I know, 727's do not need to leave the car in order for their valve bodies to be swapped out.  If you're going to build up the motor you may as well reinforce the rest of the drivetrain.  For example, there are internal components such as stronger bands and clutch packs that can be installed in the 727...

[dodge freak]

Yes you can soften the shifts up with a manual valve body-how I don't know-but a good trany man should be able too. The best part about the manual valve body is you throw away the kickdown linkage-no more adjusting it and having to work around it. I have a manual valve body and would not go back to a auto one. I have 3.91 gears and taking off in second gear is no problem, even third gear is ok. With mine you can down shift at all speeds-so long as you don't go to second gear at 90 mph. It would go what would happen not too sure. I have the reverse type with a column shift so going to third you just pull the shifter down as hard as you like-no more hitting second by mistake.

[defiance]

So just to confirm my understanding, with a full manual valve body, when you shift to 1st it is always in 1st, 2nd is always in 2nd, and D is always in drive, regardless of speed, rpm, etc?

[dodge freak]

You got it-
now on my trans in 1st gear it has no engine braking which is nice cause it does not speed the engine up when you let up on the gas. So lets say you are in second but go down to first at 60 mph-nothing will seem to happen-if you take your foot off the gas the engine will go back down to the idle speed even though you are still going 50 mph or so. Now some folks don't like having no engine braking cause it is harder to stop in first gear. So I think I seen you can get them either way. I never had a problem yet-seems like  you could but you do have engine braking in 2nd and 3rd gear with any valve body. Hope you get all this.

[RD]

a stock 727 transmission will handle around 500-550hp.  I drove a 71 dodge charger drag car for 4 seasons on a stock rebuild 727 with a 2800 stall and a b$m shift kit with the line pressure substantially higher. 

The car ran 12.17 in the quarter at 108mph with a 1.72 0-60 time. 

That is roughly 380 rear-wheel horsepower.  What that is in flywheel horsepower is roughly 490-510 hp if the 20-25% parasitic loss theory is correct.  I used that percentage to be on the safe side, I am sure others will say that the parasitic loss of the tq converter, trans, driveshaft and rear axle may be less. 

[red72chrgr]

Great question!! I sure learned a lot!! Thanks to all.

[Lightning]

is there any way to rig is so it'll engine brake in 1st and 2nd gear?

[dodge freak]

It -all valve body's-brake in second gear. For first some do but all the old ones do not. Only in first for a very short time aways if the motors gear right -4.10's .