Hawk's First 727 Transmission Rebuild

HawkRod · Nov 21, 2021

Final for now:

Planetary gears and output shaft
So both of these look to be in nice shape. I see no damage to either. However, the small block has a 4 planetary gear unit while the big block only has 3.
Both output shafts look good, although there is slightly more wear on the big block shaft.
The shaft end play (spec: .010" to .037") of the small block is .018", while the big block is .030"
Seems to me to be clear winner here: Small block

small block

big block

I guess the question here is can I simply reinsert this as an assembly or do I need to pull it apart? I'm not trying to make a major project here, and I might rather risk damaging something that has been working well. On the other hand, I'm in here now. Thoughts?

Thanks,

Hawk

zyzzyx · Nov 21, 2021

You do need to inspect the bushings, thrust washers, and the shaft for any wear or abnormalities.
Four pinions are better than three, and five are better than four, and so on. They spread the force
out and allow the trans to handle more torque.

HawkRod · Nov 21, 2021

zyzzyx said:
Just check the support hub with a Mic to make sure it's round! Use some carb Cleaner and compressed air to finish cleaning your case! Buy a new Kevlar band!

Thanks - will check roundness. And yes, the case will get Berkebile 2+2 and a wipe down!
As far as the Kevlar band: I found one at Summit for $67. That's a bit painful. Now mind you, I'm not trying to be a cheap SOB. If I need it, I need it. But if the big block band (that looks similar to the Kevlar band) is OK, can't I reuse it?

RemCharger said:
Machined surfaces should never be blasted.
The problem in this case is;
No gasket
Thin fluid
Keeping the separate circuits separated.
Who knows what servo circuit might engage some other clutch pack in the wrong gear.
Might want to read up about that area in the book.

Thanks for the heads up. The book speaks about checking the pan rail for distortion using a large fine file to file until the entire surface is flat. Mine was only off by .002" at worst, but perhaps then I will run a file over it to ensure I have done it "by the book".

zyzzyx said:
You do need to inspect the bushings, thrust washers, and the shaft for any wear or abnormalities.
Four pinions are better than three, and five are better than four, and so on. They spread the force
out and allow the trans to handle more torque.

Yeah, I was afraid someone would say to inspect it all! OK. I'll check it (tomorrow - time for beer now!)

zyzzyx · Nov 21, 2021

zyzzyx · Nov 21, 2021

I can't hold the band and look at it so I can't tell you how good it is, but you don't need to give Summit
your money. I just bought a heavy-duty band on E-Bay with a Raybestos Kevlar lining for $27.00/Free ship!
Some of this stuff is expensive and some is not!

Ghostrider 67 · Nov 21, 2021

Top of my head pal, I don't know, cant remember. I would have to grab the Hand book and read up and compare again.
Your assumptions, as you stated, all seem to be okay. It's all mostly common sense, be observant. As you are clearly doing.
The five pinion carriers are for extreme heavy duty use. I doubt you need them. I took the four pinion sets out of the trans I had from behind a 440 six pack and put them in mine. Should be fine. Don't recall what the three holes are for but my guess would be to evac fluid..& heat.

Dave6T4 · Nov 21, 2021

HawkRod said:
Me neither! But that's what is great about this site. There are people willing to help share their knowledge so I can do something like this!

Speaking of sharing knowledge. While I am cleaning the case today, a couple of questions to prepare for assembly:
Question 1:
I know I need some kind of assembly lube. The below is what I use on engines. Can I use this for the transmission or should I use something different?
View attachment 1196725

Question 2:
I have a complete seal kit as pictured below. It goes without saying that once I disassemble the other big block transmission I need to inspect parts for damage, wear, etc. But are there some parts that I definitely need no matter what?
View attachment 1196726

As always, I greatly appreciate the help!

OK. Now to get my butt outside in the cold to do a lot more boring cleaning - it's a necessary evil if I want this transmission to live more than a few miles!

Hawk

I do not see the oil pump bushing or front drum bushing in this kit. You should change them. Early 727's used a narrow drum bushing, while later (about 1970-1971) used wider bushing. There were also differences in the drums. You should also get a new sprag spring and rollers kit.

Dave6T4 · Nov 21, 2021

HawkRod said:
OK Folks, here is where I could really use the help from the experts. I want to show comparison pictures of my small block vs. big block parts. I'll add my own commentary, but since I may not know what to look for, I greatly appreciate your help to pick the best part/ subassembly for my car.

I will always post the small block first/ to the left, big block last/to the right.

Overrunning Clutch Outer Race
Both look fine to me, I see very minimal wear on either, but the small block has bigger indentations from the rollers on the spring retainer. Both inner races (and rollers/springs) look good. My vote would be for big block here.
View attachment 1197058 View attachment 1197059

Output Shaft Support
The small block seems to have more wear from the governor, and also some more wear on the front. Neither have any wear I can feel with my finger, but my vote goes for big block. Edit: Also, the inside, that supports the output shaft, is nice as well, no galling or obvious wear, although, again, the big block looks a bit better (this is not able to be seen in the pictures).
View attachment 1197070 View attachment 1197071
View attachment 1197072 View attachment 1197073

These may be no brainers, but I'd still like to boost my confidence by getting some comments from folks on the forum. Of course, if there is something that you think needs replacing, then so be it - let me know that too.

Thanks,

Hawk

The big block piece looks like the clear winner. I have an assortment of honing stones that I use to clean up machined surfaces. I have a fine flat and another small round "India" stone. These are both white stones. I also have a coarser brown "Arkansas" stone to take down high spots on oil pan, valve body separator plate, etc. Machinists use these in their work. You may be able to source these from companies that supply tool shops. I would use the small round stone to clean up the seal rings marks in the rear support and my flat white one to check for high spots on the hub end of the support. These stones are very fine and merely polish the area without taking any appreciable amount of material off.

Dave6T4 · Nov 21, 2021

HawkRod said:
Final for now:

Planetary gears and output shaft
So both of these look to be in nice shape. I see no damage to either. However, the small block has a 4 planetary gear unit while the big block only has 3.
Both output shafts look good, although there is slightly more wear on the big block shaft.
The shaft end play (spec: .010" to .037") of the small block is .018", while the big block is .030"
Seems to me to be clear winner here: Small block
View attachment 1197108 View attachment 1197109

small block
View attachment 1197110

big block
View attachment 1197111

I guess the question here is can I simply reinsert this as an assembly or do I need to pull it apart? I'm not trying to make a major project here, and I might rather risk damaging something that has been working well. On the other hand, I'm in here now. Thoughts?

Thanks,

Hawk

The 4 pinion planetary is obviously the one to use. You should pull these assemblies apart since there is a thrust plate and machined surfaces that should be checked for wear. This will be one of the easier assemblies to take apart and reassemble. Be sure to lube everything before reassembly Trans fluid is OK here. Again, I would just lightly dress any machined surface here with my flat white stone. Also, any machined surfaces in the output shaft.

Dave6T4 · Nov 21, 2021

HawkRod said:
Next set of parts:
Low and reverse drum
The big block drum has noticeable wear from the clutch, you can even feel it with your finger. On the other hand, the small block drum still has machining marks left and extremely little wear. My vote here goes for the small block drum.
However: I notice that the small block drum has three holes drilled in it, while the big block does not. Not sure why?
View attachment 1197090 View attachment 1197091
View attachment 1197092

View attachment 1197093

Low/ Reverse Band
The small block band looks like a solid piece of metal with perhaps a coating on it (?). On the other hand, the big block looks a little bit like a brake drum pad. The small block has imperfections in it, so I don't like the way it looks (see center of the picture, bottom of band). The big block band looks fine, except three of the ribs look like they have gotten very hot. Winner here, maybe big block?
View attachment 1197094

View attachment 1197095

Thanks,

Hawk

I would use the small block rear drum with the band that came with it. The drum looks brand new, with no damage from the band. Look at your other drum and the wear marks from its band. There are lots of reasons for the wear such as poor band adjustment, oil pressure problems, and just driver abuse.The holes in the drum are likely for balance. I have seen different combos of holes in these drums over the years.

HawkRod · Nov 22, 2021

Great information and feedback - thank you all.

So I have ordered the sprag spring and roller kit. I have looked for bushings, and really only had success finding the bushing kits. I may still order a bushing kit, but before I do, I need to understand better how to remove and reinstall them. I do have a 20 ton press, but it looks like there are some special parts needed to drive the bushings. Like most, I might use an appropriately sized socket, but maybe I need something more. Perhaps I should just go to a local transmission shop and have them press the needed bushings in?

I will also look for a good honing stone to polish some of the machined surfaces. Barring that, I will just use some emery cloth to touch them up.

Dave6T4 · Nov 22, 2021

HawkRod said:
Great information and feedback - thank you all.

So I have ordered the sprag spring and roller kit. I have looked for bushings, and really only had success finding the bushing kits. I may still order a bushing kit, but before I do, I need to understand better how to remove and reinstall them. I do have a 20 ton press, but it looks like there are some special parts needed to drive the bushings. Like most, I might use an appropriately sized socket, but maybe I need something more. Perhaps I should just go to a local transmission shop and have them press the needed bushings in?

I will also look for a good honing stone to polish some of the machined surfaces. Barring that, I will just use some emery cloth to touch them up.

You could stack the new bushing on the old and use your press to carefully push the old bushing out. I would be afraid that every cloth might be too abrasive.

HawkRod · Nov 22, 2021

LOL. This transmission build is getting to be a bit like my "budget" 340 build. It became a stroker, then with aluminum heads, balanced, blueprinted, etc! So much for budget!

But I hear all you guys telling me to replace stuff. I had kind of hoped to just throw together the best of the major components and go down the road. However, it does make sense to check and replace wearables while I am here. I want something reliable to get me across country next year, so I guess I need to suck it up and do what is right.

One of my current issues is that I have TWO disassembled 727 transmissions. I would like to get the big block unit back together and out of my way so I can better concentrate and work on my small block unit. To that end, I would appreciate some help making final decisions on parts selection. Once I have done that, I can put the parts I am not going to use back in the big block case.

So here goes the (hopefully) final parts selection process:
Kickdown and low/reverse servos
I think if I remember my reading correctly, that the big block kickdown servo is an early style, while the one from my small block is a newer style. I will keep both small block servos.

Kickdown servo arm
The small block has a 3.2 ratio while the big block has a 3.8 ratio. It seems that performance applications use higher ratios, so based on my reading the big block 3.8 is the way to go on my transmission.

Input shaft assembly
These look pretty identical to me. Since overall the small block seems to be in better condition, I will use it, but from an overall condition perspective, they are about the same.

Any comments regarding these final parts?

Next steps will be
(a) reassembling the big block transmission to get it out of my way
(b) starting to check and recondition assemblies for the small block transmission

Thanks everyone for your patience and for following along!

Hawk

Dave6T4 · Nov 22, 2021

HawkRod said:
LOL. This transmission build is getting to be a bit like my "budget" 340 build. It became a stroker, then with aluminum heads, balanced, blueprinted, etc! So much for budget!

But I hear all you guys telling me to replace stuff. I had kind of hoped to just throw together the best of the major components and go down the road. However, it does make sense to check and replace wearables while I am here. I want something reliable to get me across country next year, so I guess I need to suck it up and do what is right.

One of my current issues is that I have TWO disassembled 727 transmissions. I would like to get the big block unit back together and out of my way so I can better concentrate and work on my small block unit. To that end, I would appreciate some help making final decisions on parts selection. Once I have done that, I can put the parts I am not going to use back in the big block case.

So here goes the (hopefully) final parts selection process:
Kickdown and low/reverse servos
I think if I remember my reading correctly, that the big block kickdown servo is an early style, while the one from my small block is a newer style. I will keep both small block servos.

View attachment 1197435 View attachment 1197436

Kickdown servo arm
The small block has a 3.2 ratio while the big block has a 3.8 ratio. It seems that performance applications use higher ratios, so based on my reading the big block 3.8 is the way to go on my transmission.
View attachment 1197437

View attachment 1197438

Input shaft assembly
These look pretty identical to me. Since overall the small block seems to be in better condition, I will use it, but from an overall condition perspective, they are about the same.
View attachment 1197453

View attachment 1197454

Any comments regarding these final parts?

Next steps will be
(a) reassembling the big block transmission to get it out of my way
(b) starting to check and recondition assemblies for the small block transmission

Thanks everyone for your patience and for following along!

Hawk

Use the big block servos and 3.8 lever. Are you going to disassemble clutch packs to replace clutches and piston seals? Seeing the early style kick down servo makes me wonder if both the front drums are the same with the wide bushing?

zyzzyx · Nov 22, 2021

Sounds good Hawk! Yes, I hope you will be checking the clutch pack clearances!

Ghostrider 67 · Nov 22, 2021

Sounds right to me.

HawkRod · Nov 22, 2021

Dave6T4 said:
Use the big block servos and 3.8 lever. Are you going to disassemble clutch packs to replace clutches and piston seals? Seeing the early style kick down servo makes me wonder if both the front drums are the same with the wide bushing?

Will do - thanks. Yes, I'm now going to go all the way and replace all the friction material, bushings, etc. I might as well since I have gone this far!

zyzzyx said:
Sounds good Hawk! Yes, I hope you will be checking the clutch pack clearances!

I will, once I get to that part. I am first going to disassemble and redo them with fresh friction material. You're ahead of me.

There is so much transmission stuff to learn about mixing/matching parts!

Thrashingcows · Nov 22, 2021

I did my first...and so far only 727 rebuild a few years back for my 440/auto 68 T/C wagon. I priced out having it rebuilt at several shops and they were either not interested, or IMO gave me the "not interested" price tag of $1500-$2000 for a rebuild!

Having rebuilt manual tansmissions A833's, NV4500 etc I figured it couldn't be that hard, and As others have stated it was actually easier then rebuilding a manual unit.

I think for most people the auto is just slightly intimidating and therefore they choose not to do it themselves.

Great job so far!! :thumbsup:

HawkRod · Nov 23, 2021

So last night, I verified my forward drum/ front clutch retainer and also put back together the big block transmission (no pictures of this). The big block transmission will be sold as a core, but I carefully assembled it with all parts so it can be easily rebuilt. In theory, it could be run, but I would strongly suggest to anyone buying it not to do that.

Forward Drum (Front Clutch Retainer)
Here are the clutches and steels from the two forward drums:

So the big block had (unusually) 5 of each.

Here is the spring arrangement from each.

No, I didn't make a mistake. The big block only had 6 springs. A couple of people I have talked to can't figure out why.

Here is a closeup of a steel spacer from the big block. They are kind of a uniform gray, and these may be "Kolene Steel", that has a gray color and is used in high performance applications.

So, I will end up using the big block forward drum with 5 clutches. This is much better than only 3 in the small block!

So now:

I have ordered new front and rear bands, clutches, bushings and even tools to press the bushings in and out. So now I have to wait for those as the transmission will get a full rebuild. As I am able to, I will begin to rebuild my small block with refurbished parts, which (of course) will be posted here.

Thanks for the help and sticking with me!

Hawk

zyzzyx · Nov 23, 2021

HOORAY! There is light at the end of the tunnel! Glad to hear Hawk. Now to get mine changed around!

Hawk's First 727 Transmission Rebuild

Formerly hsorman

FBBO Gold Member

Formerly hsorman

FBBO Gold Member

FBBO Gold Member

Jack Stand Racer #6..and proud of it!

FBBO Gold Member

FBBO Gold Member

FBBO Gold Member

FBBO Gold Member

Formerly hsorman

FBBO Gold Member

Formerly hsorman

FBBO Gold Member

FBBO Gold Member

Jack Stand Racer #6..and proud of it!

Formerly hsorman

Well-Known Member

Formerly hsorman

FBBO Gold Member

Similar threads