Hawk's First 727 Transmission Rebuild

[71Beeper]

Here's the link to Nicks Garage video.

 

[HawkRod]

My bushings just arrived, but yesterday (without bushings in hand), I made some progress on things I could do without bushings.

If you are building a high performance transmission, the action of the front drum clutches can be tuned by tapping the hole shown below. You then put in place a NPT plug with a variable hole drilled through it to tune the rate the hydraulic fluid can push the clutches. As you can see, there is a restrictor that has been pressed in already, so I decided to leave it alone.

I decided to install the rear servo. It already has a beefier spring so it is ready to go. I replaced the bushings and reinstalled it.
Blue bushing is new, black is the old. Lip has to go face down!

Here is the rear servo installed. I used transmission fluid to lube it up.

I then decided to install some of the plugs. on close inspection, I saw a little bit of residual crud in the hole. So I cleaned some more!

I replaced the rubber seal on the shaft that holds the rear lever. Man was it hard and OLD! Definitely a must to replace this for a leak free transmission if you are doing one!

I then installed the lever and tested it using compressed air. Worked great!

Finally, I replaced the sealing rings for the accumulator and re-installed that.

So, not tons of progress but at least some!

 

[MoparGuy68]

I’ll have to read through all these posts. I’m hoping to learn how to stop a 727 from leaking fluid. And to stop fluid from leaking past the pan gasket after installing a new pan and gasket. The old cork gasket leaked so bad, it was like there was no gasket at all..

 

[66Satellite47]

I didn't like the cork gaskets at all. Used the Fel Pro style rubber composition type for decades, no real leakage problems. Make sure the pan bolt holes are not dented from over tightening.

 

[66Satellite47]

Hawk, FYI, that "center servo" is called the accumulator. Those are sealing rings, not bushings.

 

[AR67GTX]

I didn't like the cork gaskets at all. Used the Fel Pro style rubber composition type for decades, no real leakage problems. Make sure the pan bolt holes are not dented from over tightening.

Yes, I eventually replaced my pan with a new repro one but I think going to the blue rubber gasket was the big difference in stopping pan leaks

 

[Brandy]

The pan rail has to be F.L.A.T., so much so that a flashlight underneath the pan while sitting on a dead flat surface allows no light to escape. Then, don't over tighten the bolts.

 

[HawkRod]

Hawk, FYI, that "center servo" is called the accumulator. Those are sealing rings, not bushings.

Thanks for the correction. I suck at names of things. I normally look up stuff to verify the names of things but didn't this time. I have gone back and corrected the post so if someone looks at it in the future it will make mores sense to them.

Thanks for keeping me honest!

 

[Don Frelier]

I’ll have to read through all these posts. I’m hoping to learn how to stop a 727 from leaking fluid. And to stop fluid from leaking past the pan gasket after installing a new pan and gasket. The old cork gasket leaked so bad, it was like there was no gasket at all..

Are you sure the shift selector seal isn't leaking?
They can easily be confused as the pan leaking

 

[AR67GTX]

Thanks for the correction. I suck at names of things.

Don’t feel bad. There’s a guy from Europe on the Corvette Forum discussing his export 57 Corvette and he keeps referring to the kph speedometer as the “tacho”. So far no one has bothered to correct or challenge him - probably for fear they may actually use that for speedometers over there. But every time he repeats it I sort of cringe. I frequently mangle terms myself.

 

[66Satellite47]

Thanks for the correction. I suck at names of things. I normally look up stuff to verify the names of things but didn't this time. I have gone back and corrected the post so if someone looks at it in the future it will make mores sense to them.

Thanks for keeping me honest!

Just trying to help.

 

[66Satellite47]

The pan rail has to be F.L.A.T., so much so that a flashlight underneath the pan while sitting on a dead flat surface allows no light to escape. Then, don't over tighten the bolts.

A typical steel pan will defect at the pan bolt holes with most gaskets if over tightened. The bolt holes need to be checked and re-flattened.

 

[66Satellite47]

Thanks for the correction. I suck at names of things. I normally look up stuff to verify the names of things but didn't this time. I have gone back and corrected the post so if someone looks at it in the future it will make mores sense to them.

Thanks for keeping me honest!

Really good thread with the pics!!

 

[Joske2]

Don’t feel bad. There’s a guy from Europe on the Corvette Forum discussing his export 57 Corvette and he keeps referring to the kph speedometer as the “tacho”. So far no one has bothered to correct or challenge him - probably for fear they may actually use that for speedometers over there. But every time he repeats it I sort of cringe. I frequently mangle terms myself.

Thats correct. He probably is a truckie, they use the word tacho for the speedometer, because they used to register the speed and driving time on
a disk inside the speedometer, so police can check how hard and how long they have been driving.

 

[Dave6T4]

Yes, I eventually replaced my pan with a new repro one but I think going to the blue rubber gasket was the big difference in stopping pan leaks

I like the pan gasket from the A-518 transmission with the steel core and o-ringed bolt holes. They are a little pricey, but are reusable. Up here, I can only buy them at the Dodge store.

 

[HawkRod]

I had a frustrating day today. I was all excited to make good progress with the transmission today now that I received the 71 and up bushings. Well, not so fast.

Problem #1: Bushings
I started with dismantling the sun gear and shell. I then went to replace the bushings inside the gear.
The first went OK. With my cheapo bushing driver I stacked the appropriate two sized discs and tapped the bushing into place.

OK, Fine. However, the second bushing in the kit is still narrower that what I need. Old bushing is on the left and the new bushing is on the right. Damn it, I STILL don't have all the bushings I need, even though this bushing set was supposed to be for a 71 and up transmission. The pump bushing is also too narrow. I guess I'll have to just go to a local transmission shop and try to get what I need.

Problem #2: Front Drum
This is the bigger problem. I was re-reviewing some videos and information today. Each time I am able to pick out some additional details. I was watching this great video from Precision Transmission:


AT 6:15 of this video, he talks about early and late drums. Looks like my 5 clutch drum is an early drum, and that is based on it having the hole shown below. A later drum has a slot in it.

Oddly, this early drum pictured above has a later, wider bushing meant to go on the stator. Richard, from the video, states that the rings and slot (pointer in the slot) will not line up and work with the early drum.

I have reassembled the big block transmission with the pump and stator, but I am pretty sure it was a newer stator. But then, how did this work properly in the big block transmission? According to Richard, this combination should not work.
Now this guy Richard sounds like he has forgotten more about 727 transmissions than I will ever know. Who am I to doubt him? But this means that my 5 clutch pack drum I was intending to use from the big block is not usable. I either need to go back to using the 3 clutch setup from my small block transmission or try to find a drum meant for a 4 clutch setup.

So the lesson learned here is if you are mixing and matching parts, be sure you know what you are doing (unlike me!). Check everything twice to be sure!

So I guess I need a drum now

 

[Dave6T4]

Oh man, Hawk, it looks like you are in a jackpot there! I have never changed the bushings in the sun gears. I have never seen different size oil pump bushings, although I have seen them in different materials. The front drum and oil pump have to be changed in sets. You can not mix and match early and late styles for reasons you have seen. The drum you show is definitely the early style and should have a narrow bushing in it. The oil pump/drum support, I can not tell if it is early or late. Have you switched it, or kept it with the drum? What is the pump in the other trans?

 

[oldbee]

Kinda agree, it was much harder, way back with no internet;lol. Magazines and face to face talking. There's a lot we couldn't just Google. I still remember asking Gil Younger why my trans wouldn't shift into 3rd without letting off throttle a tad when racing. He didn't have answer. But with all the new stuff out there, I kinda figure it was my 5.0 lever on a hemi frt.clutch. Didn't even know that 'dvw' was alive back then! Although the magazines showed you how to do a full-manual VB back then, and it worked!

 

[HawkRod]

Oh man, Hawk, it looks like you are in a jackpot there! I have never changed the bushings in the sun gears. I have never seen different size oil pump bushings, although I have seen them in different materials. The front drum and oil pump have to be changed in sets. You can not mix and match early and late styles for reasons you have seen. The drum you show is definitely the early style and should have a narrow bushing in it.

That's what threw me. It has a wider, later style bushing in the early type drum. Earlier in this build, I just saw the bushing, so I assumed it was a later model drum. Just today when I saw the hole, something in the back of my head thought that was odd. Somehow my brain pieced together that one detail from the video I had subsequently watched. First of all, I'm glad I checked. But it also shows that knowledge is power - all these videos and stuff on the internet have value!

The oil pump/drum support, I can not tell if it is early or late. Have you switched it, or kept it with the drum? What is the pump in the other trans?

I am pretty sure both the oil pump/drum support (I think the guy in the video called it the stator) are the newer style; it is now back in the assembled big block transmission. I looked at all these parts very carefully, and if they were different styles I'm sure I would have noticed (and that is also why I assumed this drum would work OK). However, I will pull the big block tranny back apart and check it to be sure.

Assuming the pumps are the same, that means the big block tranny was running with an early style drum and a later model pump/drum support/ stator. That's not supposed to work, but it ran for quite a number of miles that way, so maybe it actually works (although maybe not in an ideal manner)?

Either way, I'm not going to take a chance so I'm going to find a later drum.

 

[Builderguy]

"But it also shows that knowledge is power - all these videos and stuff on the internet have value!" by HAWK.

Yes Sir, Hawk; when we stop learning we may as well stop living since one has learned everything there is to know. My motto is, as you have eluded to, "Knowledge is King". Never stop learning or trying new things. That is what keeps us young and full of fun. It also makes us pretty good at trivia. Keep on keeping on Sir, we are all learning something from you. Love this transmission thread.