Moparts Tech Archive

Automatic Trans.

727 Build-up Questions

Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-01-2002 09:49 AM

Hi,
My main questions are:

1. Is it worthwhile finding a solid kickdown servo piston assembly if I have an oil cushioned one(For drag racing)

2. What is the ideal amount of return springs in the top gear drum for drag racing.

3. I have a 3 clutch top gear drum; what has to be machined to accept 4.

Read further if you want to hear my story

I recently mangled the sprag which then destroyed the following; output shaft support , 1st-reverse drum, scored the output shaft, I'm not sure whether the top gear drum is alright(I don't want to take any chances) but the trans case seems fine.

My trans is behind a 383 and runs 11.1@119.5 and had these parts:

Early style pump(Short shaft) and top gear drum with 4 friction clutches and 15 piston return springs
3 pinion f & r planetaries
Controlled load kickdown servo piston, 4.2 lever, solid band
Cheetah reverse manual VB

The spare trans I pulled down was a '71 340 727. Is it best to use the oil pump, top gear drum and rear clutch drum as an assembly from this trans and put it in mine?
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-01-2002 11:41 AM

1. YES. Use both return springs. You can use the oil cushioned servo if you remove the small inner spring and use flat washers or make a shim to make the inner piston solid. However, the 2 spring unit releases the 2nd gear band faster for a cleaner 2-3 shift. I would look for the early servo. I got one from A&A, but be prepared to pay.
2. Turbo Action & A&A use 12 springs. Griner uses all 15 with their reverse manual VB. Most stock transmissions had 9.

3. You can have the drum machined for a new snap ring groove higher in the drum or step machine the thick outer plate to allow 4 discs in a 3 clutch drum or 5 in a 4 clutch drum. You have mail.

The '71+ 727's have a better pump and high drum in that the drum has a wider bushing to support the drum better and the oil slot in the drum flows more oil than the 2 oil holes of the 1970 and earlier trans. I would swap them into your tranny.

http://pages.moparalley.org/440Jim/website/id4.html

Check this site for a pic of the machined pressure plate. Scroll down to the tranny section.
John
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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-01-2002 02:35 PM

Thanks John,
1. So I can make mine solid with washers but it will only make the 1-2 shift better and the solid early unit will help both 1-2 & 2-3 shfts?.

2. With less springs in the top drum, will it help firm up the 2-3 shift?

3. My pressure plate measures .280", how much is safe to remove from this? I noticed that with the groove already in the drum(from spare trans), it clears a steel clutch plate and would allow it to spin if it located itself in it if I machined the groove higher(My earlier type drum, the groove isn't quite machined as far out(O.D) and therefore probably wouldn't allow a plate to spin)

Is there an advantage with a valve body that applies the band in 1st as opposed to the cheetah reverse pattern VB?

Does the accumulator blocker rod go between the valve body and the piston? What does this accomplish over no spring at all?

If I get hold of the early type kickdown servo piston, do the bore sizes vary year to year on the cases? I have a '76 bigblock case
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-02-2002 12:37 PM

1. You can shim it with washers to help. This helps the 1-2 shift. The 2 spring servo is better for a cleaner 2-3 shift.
2. It's a combination of springs in the front clutch and the servo for best shift timing. T/A recommends 12 springs in the front clutch and 2 servo springs. With less springs in the front clutch, the 3rd gear clutches will apply quicker, and if they apply before the band releases, you have a 2-3 bind-up.

3. Just follow the dimensioned drawing on Jim's website. It's the same as a plate offered by Turbo Action.

The low band apply in 1st helps protect the sprague from damage while in 1st. The no band apply in 1st (Cheetah and others) has a faster 1-2 shift because the low band does not have to release. Burnouts and 1st gear operation have to be done safely to prevent roller clutch damage with the Cheetah.

The rod goes between the top of the accumulator piston bore and the bottom of the piston. The spring is not used. This blocks the piston downward so no fluid pressure is used to move the piston and try to buffer the application of the kickdown band servo. Removing the spring only speeds up the application of the forward clutch going from neutral/park to a forward gear.

The servos are all the same diameter. John
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Author Topic: 727 Build-up Questions
Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-01-2002 09:49 AM
--------------------------------------------------------------------------------
Hi,
My main questions are:

1. Is it worthwhile finding a solid kickdown servo piston assembly if I have an oil cushioned one(For drag racing)

2. What is the ideal amount of return springs in the top gear drum for drag racing.

3. I have a 3 clutch top gear drum; what has to be machined to accept 4.

Read further if you want to hear my story

My trans is behind a 383 and runs 11.1@119.5 and had these parts:

The spare trans I pulled down was a '71 340 727. Is it best to use the oil pump, top gear drum and rear clutch drum as an assembly from this trans and put it in mine?

Thanks

[This message has been edited by Ilias383 (edited 07-01-2002).]

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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-01-2002 11:41 AM
--------------------------------------------------------------------------------
1. YES. Use both return springs. You can use the oil cushioned servo if you remove the small inner spring and use flat washers or make a shim to make the inner piston solid. However, the 2 spring unit releases the 2nd gear band faster for a cleaner 2-3 shift. I would look for the early servo. I got one from A&A, but be prepared to pay.
2. Turbo Action & A&A use 12 springs. Griner uses all 15 with their reverse manual VB. Most stock transmissions had 9.

3. You can have the drum machined for a new snap ring groove higher in the drum or step machine the thick outer plate to allow 4 discs in a 3 clutch drum or 5 in a 4 clutch drum. You have mail.

John

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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-01-2002 12:01 PM
--------------------------------------------------------------------------------
http://pages.moparalley.org/440Jim/website/id4.html
Your e-mail failed, so check this site for a pic of the machined pressure plate. Scroll down to the tranny section. John

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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-01-2002 02:35 PM
--------------------------------------------------------------------------------
Thanks John,
1. So I can make mine solid with washers but it will only make the 1-2 shift better and the solid early unit will help both 1-2 & 2-3 shfts?.

2. With less springs in the top drum, will it help firm up the 2-3 shift?

Is there an advantage with a valve body that applies the band in 1st as opposed to the cheetah reverse pattern VB?

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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-02-2002 05:51 AM
--------------------------------------------------------------------------------
Does the accumulator blocker rod go between the valve body and the piston? What does this accomplish over no spring at all?
[This message has been edited by Ilias383 (edited 07-02-2002).]

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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-02-2002 11:57 AM
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If I get hold of the early type kickdown servo piston, do the bore sizes vary year to year on the cases? I have a '76 bigblock case
[This message has been edited by Ilias383 (edited 07-02-2002).]

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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-02-2002 12:23 PM
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Btt
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-02-2002 12:37 PM
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1. You can shim it with washers to help. This helps the 1-2 shift. The 2 spring servo is better for a cleaner 2-3 shift.
2. It's a combination of springs in the front clutch and the servo for best shift timing. T/A recommends 12 springs in the front clutch and 2 servo springs. With less springs in the front clutch, the 3rd gear clutches will apply quicker, and if they apply before the band releases, you have a 2-3 bind-up.

3. Just follow the dimensioned drawing on Jim's website. It's the same as a plate offered by Turbo Action.

The servos are all the same diameter. John

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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-02-2002 12:45 PM

Thanks John,
So the accumulator piston even with no spring moves around enough(Up and down) to use some pressure? Does it also mean that with it blocked down there's more fluid on top of the piston just sitting there?

I also plan on putting NOS on my car, do you think it will be alright to gas the car either on launch or just after initial launch with my trans?
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-02-2002 02:48 PM

With the piston not blocked, the piston has to move and displace fluid like an accumulator, to buffer the kickdown servo. With the piston blocked, oil flows directly to the kickdown servo for faster application of the 2nd gear band.
Spraying an engine puts alot of stress on everything. If you don't use a big kit, say over 125 HP, it should be alright. If you spray it hard, you could strip the internal splines off the front carrier gear. It is only aluminum. Most big nitrous and transbrake users go with a steel front carrier for strength. John
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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-03-2002 12:27 PM

Hey John,
Do you think its worth me finding a valve body that applies the band in first, I like the idea of extra protection against sprag failure as big block cases are rare here in Australia and braking a case could put me out of racing for a far while?

What other tricks do you recommend for really hard shifts?

I noticed that the output shaft support I got doesn't fit tightly in my case and doesn't have grooves for oiling on the drum side of it, is this a problem?

If I find an early style kickdown servo piston assembly, should I use the springs that came out of that trans? Even if it only had one, or can I use one from a cushioned assembly?

In the spare trans it had a 4 pinion front gearset, should I try and find a rear one also to use in my trans?
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-03-2002 02:02 PM

Use a JVX or A&A valvebody for low band apply if you want the extra safety.
Some supports do not fit tight in the case, not a problem. The grooves help oil the drum. The factory did not groove them. Turbo Action sells a roller support for the 727 for around $88.

You can use the stock servo springs. The cushioned servo spring can be used if you need an outer spring. Turbo Action sells a spring kit if you need springs.

The rear planet does not receive as much stress as the front, so it's up to you whether you want to find a 4 pinion rear planet. Some factory transmissions came with a 4 pinion front and a 3 pinion rear.

The main ways to make the trans shift nice and firm is the VB, the servos and the blocker rod.
John
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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-03-2002 02:17 PM

Thanks John,
I've looked over the rear of my case and it seems crack free, do you think that its possible that the case and VB may have warped when the diff failed? Are gaskets a cure between the VB and case?

Should the direct clutches have grooves or squares or is it better to try and gain as much surface area and have them flat?
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John Russo
Moparts Member
Posts: 1901
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-03-2002 04:32 PM

No gaskets needed. Check flatness of valvebody attaching area on the case with a long straight edge to make sure it is flat.
I have had the best luck with the Raybestos Tan waffle clutches in the front clutch. These channel away oil during application to prevent hydroplaning of the clutches.

www.raybestosclutch.com

Also, new design clutches, but I have not used them:

www.altousa.com

Some builders use the rear clutches in the front clutch with less grooves, and they are thinner to add a friction disc easier than machining the pressure plate. I have not done this, but have heard that some racers have had good results. I have only used the Raybestos waffle frictions in the direct clutch. John
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Ilias383
Moparts Member
Posts: 154
From: Adelaide, South Australia
Registered: Dec 2001
posted 07-04-2002 02:48 AM

Thanks John,
Do you set up the clearances different for say a 4 clutch setup to a 5 in the front?
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451 Jim
Moparts Member
Posts: 1574
From: Lexington Park Maryland
Registered: Dec 2000
posted 07-04-2002 11:03 AM

For the front (direct) clutch, the stock clearance specs are:
3 disc: 0.076-0.123
4 disc: 0.088-0.145
5 disc: 0.090-0.122

However, for performance use B&M recommends 0.060-.080"

Raybestos recommends 0.008-0.012" per friction disc, so a 5 friction clutch would be 0.040-0.060" clearance.

I have 5 frictions, and my clearance is at 0.052" with the snap ring thickness I used.
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info provided by members listed above

727 Build up

Ron Bookman
New Member
Posts: 22
From: Hampton, Virginia
Registered: May 2002
posted 05-29-2002 12:45 PM

I,m in the process of building a 502 ci stroker that should put my 69 Dart into the 9's . The car weighs 3600 lbs with driver, it has an S&W rear frame with 4 link with 33 x 18.5 x 15 ET Streets. I will be using a trans brake as well. What trans mods are required to help make the transmission live longer with this combo.

Where can I purchase a bolt together sprag?

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DARTMAN928
Moparts Member
Posts: 709
From: IN
Registered: Jun 2001
posted 05-29-2002 01:55 PM

Try A&A transmissions or tranz-act. They should have them.
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hemifever
Moparts Member
Posts: 1103
From: Raleigh/Durham, NC
Registered: Jul 2000
posted 05-29-2002 03:09 PM

A&A will have probably everything you need and can probably make some suggestions on bands/clutches. The bolt in sprag is a necessity.
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info provide by members listed above

Best 727 Bands?

Mopar_Mudder
Moparts Member
Posts: 168
From: Rice Lake, WI
Registered: Nov 2000
posted 05-28-2002 06:12 PM

Ok what is my best option on 727 Bands for extreme duty in an off-road truck.lots O power big tires, ect. The reverse band will be used in first gear also.
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Dennis
Moparts Member
Posts: 6820
From: Eagle Creek, OR U.S.A.
Registered: Nov 1999
posted 05-28-2002 10:16 PM

Brand new bands for the low/reverse in the stock material is best, and Turbo Action red race lining was the absolute best I ever found. The Kevlar stuff is absolute crap, and way overblown as far as the hype goes. They are so hard that they glaze over and lose all efficiency after a short while. Dennis
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440shorty
Moparts Member
Posts: 819
From: Annapolis, MD
Registered: Apr 2001
posted 05-28-2002 10:46 PM

News flash: Borg Warner has recently released a new 727 HI-ENERGY kickdown band. The lining is dark gray in color. The high energy lining has been available for the GM 4L60-E for over a year now, and was developed to improve the quality of shifts and durability of the band, which is used in second and fourth (O/D) in the 4L60-E.
This lining is awesome. The Hi-Energy material was released for the TH200/325 recently, too, and made those transmissions shift like they never could before.

We haven't had a chance to use one yet in a 727, but I can say that it is great in other applications.

I agree with Dennis on the Kevlar -- no good.

440shorty
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64hemi
New Member
Posts: 95
From:
Registered: Feb 2002
posted 05-29-2002 07:21 AM

440shorty......I've got my transmission apart right now and this would be a great time to put the borg warner bands in. Where can I get them(from you?????)
THANKS......Terry

P.S. This is why I like this board so much because EVERYONE is willing to share information for the good of all of us. Reminds me of the old days. Didn't matter who won as long as it was a MOPAR.
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440shorty
Moparts Member
Posts: 819
From: Annapolis, MD
Registered: Apr 2001
posted 05-29-2002 07:13 PM

Any transmission shop should be able to order the Hi Energy kickdown band from their suppliers.
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info provided by members listed above

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