I need to take a big block 727 to a trans. shop to get it beefed up for an approx. 600 hp stroker motor I am building. I am using a 727 from a 1973 C-body as the core. I would appreciate any information on what to ask or expect the trans. shop to do in building the trans. for my application as I know next to nothing about building a transmission or transmission internals. Thanks in advance.

There are lots of people on here that will give you excellent advice as to when to get billet drums or which valve body to use but I suggest you research who is best at mopar transmissions.

Often you get guys who have only built GM trannies selling themselves as building anything.

I can tell you from experience there are nuances for every transmission and some shops may not understand what really is good or bad for a particular brand build.

Get references or ship it to one of the guys on here that build them and know them.

Hope it is some help.

Ask around the local Mopar crowd for recommendations of somebody local who knows Torqueflites.

Why not ask the trans shop what they plan to do then post that info here.
Let’s see how good they are.

Where are you located?

that info would be helpful, or what about a crate trans from cope or ?

For most street applications, it doesn't take much to get a 727 to handle 600 horse. What are your plans for the 600 horses? Street, track, combo?

It doesn't take much to get one to reliably take 600 hp.

I built my own with really not much more than better clutches and steels and a TA manual valvebody.

It has over 7,000 miles and hundreds of dragstrip passes. I do try to inspect it at least annually as we have started spraying a 250 shot on top of the 600 n/a.

Low band apply valvebody and NOT doing 1st gear burnouts are keys to longevity with the 727.

Another option - rebuild it yourself. There are some excellent 727 build books, plus many experts on here (some have responded). There is a 727 rebuild instruction here: https://www.mopar1.us/727rebuild/

Used Pat Blais, otherwise known as Torqueflite Patty, as a resource for both parts and advice. Great guy, but believe he is retired now tho. Between the 727 books and his advice, managed to rebuild my first 727 to mate with a healthy 440-6. I would email pix/descriptions to Pat and he would evaluate condition and/or remedy if issues were apparent. Upgraded to 4 pinion planetaries, shift kit, better clutches/steels, deep pan, and some new parts, but otherwise no major mods. The advantage, of course, is when completed you possess more knowledge to troubleshoot/repair/upgrade the 727 as needed. As an option you could run a build thread on here and the experts could chime in as needed.

I agree. Post your application/plans/etc.

But to get things started, I suggest.
1) Good quality clutches. Borg Warner, Raybestos, Alto Red Eagle
2) Have them replace all the bushings now. Then it may never need them again (except the converter bushing might need replacing again). Added labor will apply.
3) Have them replace all the thrust washers now. Again, they will last a long time. Parts are inexpensive, and no added labor.
4) I prefer the driveshaft seal with the dust boot. Most kits only come with a lip seal and no dust boot.
5) A little more line pressure than stock. At least turn up the factory valvebody regulator some. Shift kits typically recommend this. An aftermarket valve body typically is already higher pressure.

I'm going to be needing a big block 727 soon also and I think I'm going to skip getting a core for local shop to build. I've lost confidence in local shops that were at one time good. I'm going to buy one that's built and have shipped. Possibly B&M or TCI. I have a TCI small block 727 and it's been very good for years/miles.

the book by carl monroe is very good, and the book offered by the ATSG [Automatic Transmission Service Group] is good as well, so the money spent on these two books is a bargain and a half if you want to rebuild your transmission yourself.
the 727 is arguably the easiest transmission to rebuild, and requires only a few "special" tools that can be easily fabricated, even if one has very limited fabrication skills.
i am no transmission expert by any stretch of the [my] imagination, but i have done several over the years, and have been successful.

On your deal I would contact Pro Trans in Texas (661-940-7400) and have them build yours or send you a complete rebuild kit with instructions for you or who you choose to use to do the installation of the Pro Trans parts. They are the best in the World on 727,904 and most other trannies built for Hi Po use including their famous Pro Flyte 3 speed racing trannies

I hear people talking about big block and small block 727's. I've purchased two 727'sto use on a couple of cars. The pan is the same on both but they different measurements on the maiting face at front. Are there numbers or codes I should look for on the block to decide which is which? The cars are a 40 Desoto and a 47 Desoto suburban by the way. Is there a way to post pictures on here, I will if it can be done and someone tells me how.

Easiest way to ID the BB and SB 727 is by the bellhousing .

On the reply page, look for ATTACHMENT MANAGER near the bottom left. Use it to attach pics.

Or by looking at John's pictures, the starter location on a small block is below the center line of the bell (left side picture), and a big block trans has the starter location on the bell centerline (the bell on the right is a big block trans)'.
Just a side note, if the starter location is above the bell center line, it is a slant 6 trans (though the very early slant 6 727 used a small block trans and relocated the starter). Gene

yes, quick look has the small block starter nose locating hole at 4 o'clock, while the big block starter nose hole is at 3 o'clock.

Top of my list for ANY 727 is an aftermarket front drum.

Insist on installing a bolt in sprag. I never did until I had a sprag explode on me. It was very violent but luckily the car had skinny rear tires so they dragged instead of causing too much damage inside. The trans case amazingly survived.