Hawk's First 727 Transmission Rebuild

[66Satellite47]

Hawk, you definitely need to use to use the matched set of front drum and support either early or late. The support is a different length for early narrow bushing compared to the late model support that goes with the wide drum bushing. Not sure how a mismatched setup could work. You support sure appears to be a late model wide bushing style.
Also, I would not consider using a three disc clutch drum for anything but a very low perf application. You need a four disc drum and either a standard four disc or the special five discs that fit into the four disc drum.
I've never replaced a planetary sun shell bushing, in all the 727's I've done. They didn't seem to ever be at all worn. Only the thrust washers sometimes. I'm not sure the two bushing you show in your pic are for the sun shell. I don' recall any of the kits I've used providing sun shell bushings.

 

[HawkRod]

I've never replaced a planetary sun shell bushing, in all the 727's I've done. They didn't seem to ever be at all worn. Only the thrust washers sometimes. I'm not sure the two bushing you show in your pic are for the sun shell. I don' recall any of the kits I've used providing sun shell bushings.

Maybe that's my issue. The bushings looked fine actually, but I guess I was in a "replace everything with new" mode. No good deed goes unpunished!

 

[AR67GTX]

I remember when I rebuilt mine, I was told most of the bushings should be fine without replacing. I looked at them closely, measured them and replaced a number of the but not others - I can’t recall exactly which ones without going to my old thread. One thing that kind of amazed me was how the entire assembly of shaft, drums, clutch packs, etc wan’t exactly a rigid assembly, there’s some wiggle in it, it struck as more so than a manual transmission. But, it all works fine and smooth when it’s all buttoned up and running.

 

[Dave6T4]

I don't usually change the rear tailshaft housing bushing, either, unless it really looks bad. They are a brute to push out and get back in. I always change the front pump bushing and front drum bushing, as they usually show wear. When you have the pump apart, check rotors for wear, and try to keep track of which side is top or bottom, to reinstall in pump as they came out. Keep these as sets; don't mix and match them.

 

[66Satellite47]

I only replaced, one maybe two tailshaft bushings. But most front pump bushings. When the Babbit versions were available, always used those.
One summer I had constant front seal leaks, replaced the seal and bushing, but still leaks. Pulled the trans three times one week. At the end of the season took the 727 out, disassembled, and checked the case for the front pump bore. Turned out it was egg shaped. Tossed the case, built another one, never leaked again.
Never had an issue with the pump rotors being up or down, just be sure the clearances are good. My opinion.

 

[HawkRod]

So I managed to get another sun gear with both bushings in it today. The bushings are in great shape so I will use that.

I still need to get a good drum, but my father-in-law might have one. But, my project needs to go on hold for a few days since I am headed to the PRI show in Indianapolis. I'll be back at this Transmission project on Monday!

 

[Nxcoupe]

Hawk, look up 'whatever it takes' trans parts on the internet. WIT is what everyone around here calls them. They seem to have parts for every trans ever built. They also have tons of information as well. I'm buying a trans bench so I can start doing some auto trans work. Good luck! Keep going.

 

[HawkRod]

OK, folks. Sorry for the break in progress but I went to the PRI show in Indianapolis last Wednesday, and have been running around doing some other things. In the mean time, I believe I have secured all the parts that I need (haha, likely Murphy will rear his ugly head and make that statement incorrect!).

OK, so some more picture dumps of what I did. I started refurbishing the planetary gear sets, so this post will contain disassembly pictures.

First, measure the end play clearance here:

I measured .019" (picture shows .018", but I was able to measure .019" after this picture); the spec is .010" - .037". So mine was likely not overly worn, but it came apart anyway.

First, remove the snap ring:

This is a shot with the planetary slid out

I then removed the "front annulus gear". Note bushing behind it. Mine had three tabs.

I then pulled off the driving shell and sun gear assembly. Note bushing and thin thrust plate.

I then slid out the rear planetary. Note the bushing shown here is the same one shown in the previous picture with how it mounts to the planetary.

Finally, the rear annulus gear slides off.

Now everything is disassembled so I can check it and rebuild it.

 

[HawkRod]

OK, so now to checking and refurbishing the planetary gear assembly:

First thing is making sure all the finished surfaces (that bushings ride on) and splines are in decent shape. They were OK on this shaft. The hole I am pointing to at the end of the shaft is a feed hole for fluid. You must make sure these passages are clear.

In this picture, my fingers are pointing to some of the holes that supply fluid. All these must flow well.

I sprayed 2+2 in the holes and then shot compressed air into the feed hole (and backwards too), making sure all these passages were clean and clear.

I then cleaned and inspected all parts. All splines and teeth need to be in good shape, and wear surfaces need to be smooth and not gauged up. Make sure the big lugs on the driving shell and rear planetary are nice a square and not rounded off.

Once the parts pass inspection and are cleaned, I started assembling them back together.
I lubricated and installed the thrust washer in the rear annulus gear.

Then I lubed up the rear planetary. Note that each small gear should be wiggled and spun to make sure the needle bearings are OK.

My bushings actually looked fine, and the difference in thickness between the old and new bushing was minimal, confirming that they probably could have been reused. But I had new ones and replaced them anyway.

Here is the rear annulus gear and planetary assembled with the bushing. Everything gets lubed!

Next post will continue the rebuild...

 

[HawkRod]

Planetary Gear assembly rebuild continued...

I then shot myself in the foot. Notice the bushing in the sun gear:

I got ready with my bushing driver to drive on new bushings and removed the old ones from the sun gear. The old ones looked fine, but why not replace them with new?

Well, in this picture you see the old (taller) vs. the new bushing I had. I went to a few transmission shops and no one seemed to have it. But one shop had an old sun gear with what looked like nearly perfect bushings. So I used that.

So I reinstalled the sun gear into the driving shell and called it a day! I did replace the flat bushing shown in the picture below.

I then lubed and installed the front annulus gear and planetary in reverse of how I took it apart.

I installed the front snap ring

I also installed the small bushing that goes on the front with a new one. Again, the old looked fine, but since I had new, I replaced it (old bushing is shown in front).

Finally, I checked the end play of the unit. It was .016", so well within the spec of .010" - .037".

This assembly is now done and ready to install in the transmission!

 

[HawkRod]

OK, on to the servos.

I replaced all lip seals and steel sealing rings on the servos.

I also replaced the small O-ring that seals the shaft of the low/ reverse servo lever. When I took the old one off, it was hard as a rock, so good I did this or the tranny likely would have leaked there.

Once the servos were installed (with lube, of course), I tested them using air to ensure that actuated the levers as they should.

Here is a picture with the servos almost fully installed. The front servo is a new one I got from @Dave6T4

Here is a shot with the servos fully installed. Note also that I slid in the planetary assembly into the case as well.

Now on to the front drum!

 

[Dave6T4]

OK, on to the servos.

I replaced all lip seals and steel sealing rings on the servos.
View attachment 1208635

View attachment 1208639

I also replaced the small O-ring that seals the shaft of the low/ reverse servo lever. When I took the old one off, it was hard as a rock, so good I did this or the tranny likely would have leaked there.
View attachment 1208637

Once the servos were installed (with lube, of course), I tested them using air to ensure that actuated the levers as they should.
View attachment 1208638

Here is a picture with the servos almost fully installed. The front servo is a new one I got from @Dave6T4
View attachment 1208640

Here is a shot with the servos fully installed. Note also that I slid in the planetary assembly into the case as well.
View attachment 1208641

Now on to the front drum!

Hi Hawk. It looks like it is coming along great. I would leave the spring off the accumulator piston, though.

 

[HawkRod]

Hi Hawk. It looks like it is coming along great. I would leave the spring off the accumulator piston, though.

Yes, the spring was missing when I started, but I put one there as a reminder. The transmission that is currently in the car will donate the valve body - it is one that I modified many years ago and really like how it performed. Once I get the VB out I will go through the instructions again to make sure (a) everything is set as needed and (b) all the valves move freely. I believe they state to discard the spring, so I will do that then.

Thanks for following along and keeping me out of trouble!

 

[Nxcoupe]

OK, on to the servos.

I replaced all lip seals and steel sealing rings on the servos.
View attachment 1208635

View attachment 1208639

I also replaced the small O-ring that seals the shaft of the low/ reverse servo lever. When I took the old one off, it was hard as a rock, so good I did this or the tranny likely would have leaked there.
View attachment 1208637

Once the servos were installed (with lube, of course), I tested them using air to ensure that actuated the levers as they should.
View attachment 1208638

Here is a picture with the servos almost fully installed. The front servo is a new one I got from @Dave6T4
View attachment 1208640

Here is a shot with the servos fully installed. Note also that I slid in the planetary assembly into the case as well.
View attachment 1208641

Now on to the front drum!

So a 3 gear planetary came out and a 4 gear went back in?

 

[HawkRod]

So a 3 gear planetary came out and a 4 gear went back in?

So there are two transmissions in play: A big block 727 transmission that had been built to live behind a 500 Cubic inch stroker, and a small block 727 transmission that is the original numbers matching transmission for my 73 Road Runner. (There is also a 3rd transmission too, that is the small block 727 transmission that is currently in the car).

Anyway, surprisingly the big block had a 3 gear planetary while the small block had a 4 gear planetary. In building my transmission, I am taking the best components from both transmissions, so obviously the 4 gear from the small block went back in.

 

[66Satellite47]

Hawk, Not sure why the BB 727 was built that way, 5 disc front clutch but 3 pinion planetary. Different builders have different approaches. I've almost always used a 5 disc front clutch(Turbo Action big spacer) with both 4 pinion planetaries. My approach. Last several years used the Cope thin disc/steel combo in the OEM 4 disc front drum. That seems to work really well.

 

[HawkRod]

Hawk, Not sure why the BB 727 was built that way, 5 disc front clutch but 3 pinion planetary. Different builders have different approaches. I've almost always used a 5 disc front clutch(Turbo Action big spacer) with both 4 pinion planetaries. My approach. Last several years used the Cope thin disc/steel combo in the OEM 4 disc front drum. That seems to work really well.

So I finally figured out the 5 clutches in the front drum. It is an OEM 4 disc front drum. When I initially inspected the drum, I measured only the top clutch - it is the standard front drum thickness (~ .095"). Then I counted the clutches. Great! A 5 clutch drum!

Wrong. It is an OEM 4 disc front drum. If you look at the picture below, they used 4 thin and one thick clutch in order to fit 5 clutches into the drum and get the proper clearance. Based on what I have read, this is a common way to fit more clutches in a stock drum. From what I have heard from the previous owner, this setup worked well.

Based on my belief that it was a 5 clutch drum, I ordered five .096" clutches for the drum. But 5 clutches will not fit in the drum! Pictures coming soon, but I have placed 4 standard clutches (and steeels) into a 4 clutch drum. I figure this is best for longevity. Since this engine makes somewhere around mid 400's horsepower, I assume 4 clutches will be fine.

I welcome comments and thoughts on my approach.

 

[66Satellite47]

Hawk, four good red (Raybesos style) clutches with good or new steels will work just fine for a 450-500 HP combo. I have always used the selective fit snap rings to get the clutch pack clearance where I wanted it. I used the Tubo Action modified top steel to get five clutches in the four disc drum. That was for my 500-600HP drag motors. A four disc red(HP) clutch disc is just fine.
FYI the only OEM five disc drum was the Hemi which used a wider band. That drum was heavier and unique.

 

[HawkRod]

Hawk, four good red (Raybesos style) clutches with good or new steels will work just fine for a 450-500 HP combo. I have always used the selective fit snap rings to get the clutch pack clearance where I wanted it. I used the Tubo Action modified top steel to get five clutches in the four disc drum. That was for my 500-600HP drag motors. A four disc red(HP) clutch disc is just fine.
FYI the only OEM five disc drum was the Hemi which used a wider band. That drum was heavier and unique.

Thanks. Yes, I have the good red clutches and good steels, so hopefully that will be fine.

Right now the clearance on my front drum is .112". I have read the spec is .050" to .150". This still seems on the looser side, but I only have two choices for the top snap ring. The thin wavy ring (.112" to the top of a "wave") and an old style solid snap ring. I don't remember the exact measurement of that, but it was less than .050".

 

[HawkRod]

I have posted above a couple of details about my front clutch pack, but haven't yet had time to post all the pictures - so here they come!

Font Clutch Pack:
First, there are old style drums and new style drums. The old style drums have a hole in them for fluid flow. The new style has a slot. Here is a picture of an old style drum (pointer showing the hole).

I have been told that the old style drum is NOT COMPATIBLE with a new style stator. It has to do with the distance between the seals.

So, I had to obtain a 4 disk newer style drum with a slot. The first order of business was to replace the bushing with a new one.

A book I have also talks about chamfering the two sides of the bushing. Not sure why, but I did this. Note also in this picture the slot (below the bushing) vs. the old style hole.

I replaced the two lip seals in the piston (lip pointing downwards), inserted it, and placed 10 springs into the drum.

To compress the springs and install the spring retainer and snap ring, I made my own little jig. It was simple, but worked fine. I simply put three 7/16" bolts into a block of wood spaced evenly around the wood to push down on the retainer.

I then inserted 4 clutches and 4 steels and installed the wavy snap ring. Measurement is taken from the top of a "wave" down.

Here is a shot of my actual final measurement: .112" I messed up and should have taken this measurement when dry stacking the clutches, so I tried to push down on the clutch pack to get a decent measurement.