Hawk's First 727 Transmission Rebuild

[HawkRod]

Success (I believe)!

So I tried to adjust the front band a half turn. It didn't work and just seemed to cause some weird issues in the 1-2 shift. So I bit the bullet, put the band back the way it was and pulled off the pan and valve body.

Once the pan was down, I had to pull out the "E" clip that connects the shifter to the park lever rod. The park lever rod is not easy to insert into the transmission due to the Gear Vendors tail shaft, so it was easier to pull off the "E" clip and drop the valve body. In the picture below, my finger in generally pointing in the direction of this "E" clip, but it is not easy to see in the picture (the transmission needs to be in "1" or first gear to make this rod readily accessible).

Once the valve body was out, we had to come up with a way to pull the restrictor out (as seen in post 178 above). I found a larger wood screw and simply turned it into the opening of the restrictor. Since it was pressed in initially, I then simply grabbed the screw with a pair of pliers and hammered down on the pliers. Success! The picture below shows the screw and the restrictor plug.

Here is a close up of the restrictor plug. The original hole was square - you can see this got beat up as we worked to get it out.

We then reassembled the transmission and took it for a drive. The "engine flare" was gone and the transmission shifted nicely from first to second to third at both a light throttle and a medium throttle (full throttle not yet tested).

So the problem I had earlier is GONE!!!

Now, mind, you, it is still early. I am not ready to declare this project a success yet, but the test drive this evening was a success. Now to drive it some more over the next few weeks (depending on acceptable weather) and see how it performs.

So far so good! Thank you again for the FBBO brain trust helping me through this project!

Hawk

 

[Dave6T4]

I am glad to hear that your transmission project has worked out for you. Once you have gone through this, you have gained quite an education.

 

[66Satellite47]

Hawk, I'm very happy that you were successful. Building a performance 727 sure is a learning experience. I'm going to go back & look at the hydraulic circuitry diagrams and see if I can understand what that restrictor was supposed to do. If I recall, I don't think I used the restrictor on my TransGo kit build. Enjoy the results of all your work!

 

[451Mopar]

The restrictor slows the front clutch application as far as I know.
On one of my transmissions I even went and tapped the forward clutch apply hole in the case to accept an 1/8" aluminum npt plug that I could drill to different sizes.
I ended up just leaving the plug out with no restriction?

 

[66Satellite47]

That sort of makes sense, if you have a low perf front drum with less than 10 springs. IIRC the passage in the valve body that gets drilled out, allows higher volume (higher pressure??) to the drum. Thanks

 

[451Mopar]

Yes. I think the number of springs in the drum would make a difference if the restrictor is needed?

 

[HawkRod]

Hawk, I'm very happy that you were successful. Building a performance 727 sure is a learning experience.

Thank you, and thanks for all your help too!
I can't quite yet declare victory, as I literally have two trips around the block as my testing. But with the snow, it will take a few days until things are cleaned up enough so I can drive it. Hopefully everything continues to behave well!

I'm going to go back & look at the hydraulic circuitry diagrams and see if I can understand what that restrictor was supposed to do. If I recall, I don't think I used the restrictor on my TransGo kit build. Enjoy the results of all your work!

The restrictor slows the front clutch application as far as I know.
On one of my transmissions I even went and tapped the forward clutch apply hole in the case to accept an 1/8" aluminum npt plug that I could drill to different sizes.
I ended up just leaving the plug out with no restriction?

That sort of makes sense, if you have a low perf front drum with less than 10 springs. IIRC the passage in the valve body that gets drilled out, allows higher volume (higher pressure??) to the drum. Thanks

Yes. I think the number of springs in the drum would make a difference if the restrictor is needed?

I perhaps shouldn't even open my mouth here as I am still a novice transmission builder, but here is my understanding:
First, when the transmission shifts from 2nd to 3rd gear two key things happen:
(1) The second gear/kickdown band starts to release.
(2) The clutches in the front drum begin to engage.

This little dance needs to be timed well. If (1) happens too fast compared to (2), then you will have the problem I had, which is described as "engine flare". It is characterized by the engine revving up in RPM for a split second before 3rd gear engages.

On the other hand, if (1) happens too slow compared to (2), then you will have a momentary bind as the band and clutches are acting against one another.

So the bottom line is the timing of (1) and (2) needs to be consistent. If you speed up or slow down the band then you need to address the clutches, and vice versa.

The springs in the front drum act to resist the application of the clutches. So all other things being equal, more springs = more time before they engage. So for example, if you have more springs (I put in 10), then there either needs to be more flow and/or more pressure to engage the clutches as quickly as if there were 6 springs. That plug that I pulled out restricts the flow so it slows the application of the clutches. With a slower acting kickdown/ second gear band, that worked great. But when the kickdown/ second gear band sped up, the clutches became too slow. So I had to speed them up by removing the restrictor plug. This allows more fluid to flow in a shorter amount of time, speeding up the application of the clutches.

Anyway, that is the way I understand it. I'm others will correct me if I have any details wrong.

 

[451Mopar]

I'm no expert. I have consulted several profession trans builders over the years and they really helped me out.
Chris Andrews an Andrews Racing Transmissions was a great resource to me as was the late Steven "Steve" Doughty, RIP.

 

[HawkRod]

More testing - and some adjustments???

So the weather today is sunny and cold, but there is still lots of salt and crap all over the roads from the snow, then the rain, then the freezing rain. But the he77 with it, I took the car on a little bit longer drive to test the transmission (maybe 4 miles or so).

Bottom line: Everything seems to be working OK. Reverse and forward gears work fine. The "engine flaring" that was present before I pulled out the plug seems to be gone. There are no weird noises and no leaks that I can see so far. However, I have noted some differences in behavior from my previous transmission.

• 1-2 and 2-3 shifts occur later than before. This is likely the new governor, and this is a GOOD change. previously, it shifted way too early and I was in third gear by 15 MPH. So I am really happy about this change!
• The 1-2 shift seems to be "less crisp" than it used to be. If I accelerate slowly, there is no noticeable difference. But if I use the Slap Stik and shift it manually from 1-2 at a moderately aggressive throttle (~3000 RPM), the 1-2 shift is "less crisp". My old transmission used to aggressively shift into second gear. Now, there is a bit of "comfort shifting" that seems to be there. Not slipping mind you, but just a nicer 1-2 shift you might expect out of a luxury car. But I don't want that out of my hotrod!

So overall things seem to be good, but I guess I need to do some more reading on the 1-2 shift and try to discover why it might be less aggressive than before. Also note that I have the exact same valve body that I had in the old transmission, without any (known) changes. Could this just be the kickdown band needing to be tightened a little bit? Time to research...

As always, if anyone has any suggestions for things to check, I'd greatly appreciate it!

Hawk

 

[ct71rr]

Nice work and thank you for posting this! Tons of great info. Although, I did just watch an episode of Wheeler Dealers and Mike Brewer rebuilt a 727 for a coronet 500 in about 10 minutes without any experience, just sayin’.

 

[HawkRod]

Nice work and thank you for posting this! Tons of great info. Although, I did just watch an episode of Wheeler Dealers and Mike Brewer rebuilt a 727 for a coronet 500 in about 10 minutes without any experience, just sayin’.

Haha, well, I am just not as good as Mike Brewer at finding deals OR building transmissions! But glad you enjoyed the thread.
(Although Mike Brewer plays a silly kind of act on the show, I actually think he is a pretty smart dude. Wheeler dealers is/was one of the better shows, IMHO, because they showed how to fix things and why.

 

[451Mopar]

On the 1-2 shift, I don't recall all this thread, but I though you mentioned a "Red" front servo spring? Not sure how stiff the spring is, and I don't recall if the accumulator was blocked?

 

[66Satellite47]

That servo spring does seem questionable, only since I don't know what it is. It may not be a match for your valve body. Or the valve body may not be a match for the rest of your combo.

 

[HawkRod]

On the 1-2 shift, I don't recall all this thread, but I though you mentioned a "Red" front servo spring? Not sure how stiff the spring is, and I don't recall if the accumulator was blocked?

That servo spring does seem questionable, only since I don't know what it is. It may not be a match for your valve body. Or the valve body may not be a match for the rest of your combo.

Thanks guys. Yeah, I have been looking into what the issue could be. Again, to be clear, this is not a major problem with the transmission or its operation, but more that it is not shifting 1-2 as firmly as I would prefer. Based on my very limited testing so far, I feel like I could drive the transmission just the way it is without issue. But I would still like to improve the 1-2 shift if I can. Plus, it is good learning for me (and perhaps some others who may read this thread).

In doing some reading, I didn't find anything that seemed to be an "aha moment" that indicates where the problem could be. Things that seem like they are possibilities: (1) the servo/ spring for the kickdown band (and perhaps the associated 3.8 lever I swapped in), (2) the band adjustment itself and (3) overall pressure within the transmission.

For the servo/ spring: I got that from @Dave6T4 and it is a new A&A Transmission "red spring" later style servo piston assembly. He has used this successfully on many builds, so I wouldn't think it is an issue by itself. However, perhaps the overall combination is not working together in an ideal way.

Here is my plan for a path forward:
(a) I will try a minor band adjustment (tighten) and see what the results are. Maybe only a quarter turn or so. This is an easy thing to try, so it seems like a good start.

(b) I will check the pressure of the transmission (this would have been ideal to do anyway). I just need to scrounge up a gauge that will work. I know I have an oil pressure gauge, but I think I need a gauge that can read higher than that can.

(c) If none of the above two things yield any results, then I may try swapping out the front servo spring that I had in my old transmission and see what happens.

Some of this might take a couple of weeks, as I now have my neighbor's 64 Impala SS on the lift - we are swapping out his 2 speed Powerglide for a overdrive (I seem to be stuck on transmissions lately!)

Of course and as always, I appreciate any comments anyone may have...

Hawk

 

[Dave6T4]

The only troubles I have experienced with the 1-2 shift is when the rear servo has not had the cushion spring blocked with a .250" spacer. The servo has to come apart by removing the small " C" clip. When using the shift kit, the 1-2 shift seems to "fight" itself, without this mod. I set the pressure with a 5/16" drill bit between the cage and the threaded nut plate. Don't be afraid to give it an extra turn counter-clockwise to raise pressure.
I try to use the 4.2 lever in my builds, but have also used the 3.8 lever whenever the transmission already had this one. I have never had a complaint in using the "red spring" servo to replace the newer factory controlled load front servo. When using the older thin pin servo, I omit the outer spring.

 

[HawkRod]

The only troubles I have experienced with the 1-2 shift is when the rear servo has not had the cushion spring blocked with a .250" spacer. The servo has to come apart by removing the small " C" clip. When using the shift kit, the 1-2 shift seems to "fight" itself, without this mod. I set the pressure with a 5/16" drill bit between the cage and the threaded nut plate. Don't be afraid to give it an extra turn counter-clockwise to raise pressure.
I try to use the 4.2 lever in my builds, but have also used the 3.8 lever whenever the transmission already had this one. I have never had a complaint in using the "red spring" servo to replace the newer factory controlled load front servo. When using the older thin pin servo, I omit the outer spring.

Dave, thanks for your thoughts and help here as well!

My rear servo definitely has had the cushion spring blocked with a .250" spacer, so that should not be the issue.

I DO have to check the pressure using the 5/16" drill bit. I left it as it was, but this may not have been set right, so the pressure certainly could be an issue. My bad for not explicitly checking and setting this - I wanted to be sure my original valve body assembly was exactly the same as before so I left this as is. Now I may be paying the price for it.

As I stated, I can't image that the red spring servo is an issue. So I think my two primary targets here to tweak the 1-2 shift are (1) the band adjustment (just because it is easy) and (2) checking and potentially setting the pressure.

While doing (2) is not particularly time consuming, it is a mess. I guess I might have to drop the pan again and take an ATF shower....

 

[451Mopar]

I normally use the servo spring(s) that come with the FT-2 Shift kit?

 

[qkcuda]

Time for a drain plug Hawk

 

[HawkRod]

I normally use the servo spring(s) that come with the FT-2 Shift kit?

I put a shift kit in the car around 1982. I used whatever springs were included with the kit and I was always happy with the way it shifted after that. When I rebuilt the transmission just now, I used a new A&A Transmission "red spring" later style servo piston assembly for the kickdown band. So yes, I guess it is now different than what I had after I installed the shift kit. If the band and pressure adjustments do not firm up the shifts, then I will try my old servo and spring. Some experimentation to get the right combination of parts might be needed here!

Time for a drain plug Hawk

It HAS a drain plug! But the damn valve body drips like crazy for a long time after the ATF had been drained and the pan dropped. I inevitably stick my big, fat head right under a drip that is about to happen and get an ATF shower...

 

[mach123]

Hawkrod
Is there a specific upgrade kit you can put in the 727,
Or just need to source out individual parts. I will be at 550
hp ish, and like to do tranny soon. Thx