TH400 rebuild tech

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m (→Rear planetary setup)
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[[file:Reaction_tube.jpg]]
 
[[file:Reaction_tube.jpg]]
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===Center support assembly===
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It is best to have the center support already ready.
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The center support houses the intermediate apply piston, supports the direct drum. It has sealing rings that seal it to the direct drum, allowing it to transfer fluid to the drum to apply 3rd gear, and reverse.
 +
Disassemble, clean, and re-assemble using new lip seals. Pay attention to the orientation. Use the old lip seals to be sure you select the properly sized new seals.
 +
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[[File:Center_support_rings.jpg]]
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Install the piston using a lip seal installed or feeler guage, be sure the piston depressions align with the depressions in the center support, and it helps to use a tilting motion as you install it sometimes.
 +
You can also use thin plastic (cut from a large plastic soda bottle) as a seal protector/installer or the proper Kent-Moore J-tools.
 +
 +
Once the intermediate apply piston is installed and the return springs, guide, retainer plate and snap ring, you must install the center support to direct drum sealing rings.
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There are 3 choices here.
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Solid teflon is on the left, then scarf cut teflon, then cast-iron.
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[[file:Sealing_rings.jpg]]
 +
 +
Cast iron is what most kits will contain, and what was used stock in most TH400's.
 +
Scarf cut teflon was used on later model Th400's.
 +
Solid teflon is used on 4L80's and is interchangeable.
 +
I prefer solid teflon, although it is the most time consuming type.
 +
Cast iron is the easiest and will work fine for most applications but if using any type of valve body that will not require a modulator teflon is best as it will prevent wear on the direct drum.
 +
If using teflon, be sure there are no burrs on the center support ring grooves.
 +
Installing the teflon rings requires a protector to prevent cutting or gouging them, and a sizing device.
 +
It helps to heat the rings in hot water before installing so that they will stretch easier.
 +
I use a piece of plastic (from a paint can cap) that is cut to size to install and size the rings. Leave it on until you are ready to install the direct drum.
 +
 +
Notice I left one sealing ring off, 2nd from top groove. This groove seperates the direct (3rd gear) and reverse feeds from each other. When dual feeding the directs (as done in this build), this sealing ring is not necessary. Dual feeding the directs on a Th400 will be covered in more depth in another section.
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[[File:Center_support_rings.jpg]]
  
  
 
Also of note,
 
Also of note,
 
Pictured is a late style reaction carrier and an early style. I believe the early style was only used on 1964-1966 models. Notice the actual sprag type element used on the early style on the right. I prefer these type for high-HP transbrake builds although not mandatory.
 
Pictured is a late style reaction carrier and an early style. I believe the early style was only used on 1964-1966 models. Notice the actual sprag type element used on the early style on the right. I prefer these type for high-HP transbrake builds although not mandatory.
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[[file:planets.jpg]]
  
  
  
 
My "compressor/sizer" for the sealing rings.
 
My "compressor/sizer" for the sealing rings.
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[[file:Center-support-compress.jpg]]
  
 
Next, you will finish assembling the rear portion for installation into the case.
 
Next, you will finish assembling the rear portion for installation into the case.
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This part is a stock 4L80 part available at a GM dealership.
 
This part is a stock 4L80 part available at a GM dealership.
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Edit/Delete Message
 
  
−
===Center support assembly===
 
  
−
It is best to have the center support already ready.
 
−
The center support houses the intermediate apply piston, supports the direct drum. It has sealing rings that seal it to the direct drum, allowing it to transfer fluid to the drum to apply 3rd gear, and reverse.
 
−
Disassemble, clean, and re-assemble using new lip seals. Pay attention to the orientation. Use the old lip seals to be sure you select the properly sized new seals.
 
  
−
[[File:Center_support_rings.jpg]]
 
−
 
−
Install the piston using a lip seal installed or feeler guage, be sure the piston depressions align with the depressions in the center support, and it helps to use a tilting motion as you install it sometimes.
 
−
You can also use thin plastic (cut from a large plastic soda bottle) as a seal protector/installer or the proper Kent-Moore J-tools.
 
−
 
−
Once the intermediate apply piston is installed and the return springs, guide, retainer plate and snap ring, you must install the center support to direct drum sealing rings.
 
−
 
−
There are 3 choices here.
 
−
 
−
Solid teflon is on the left, then scarf cut teflon, then cast-iron.
 
−
 
−
[[file:Sealing_rings.jpg]]
 
−
 
−
Cast iron is what most kits will contain, and what was used stock in most TH400's.
 
−
Scarf cut teflon was used on later model Th400's.
 
−
Solid teflon is used on 4L80's and is interchangeable.
 
−
I prefer solid teflon, although it is the most time consuming type.
 
−
Cast iron is the easiest and will work fine for most applications but if using any type of valve body that will not require a modulator teflon is best as it will prevent wear on the direct drum.
 
−
If using teflon, be sure there are no burrs on the center support ring grooves.
 
−
Installing the teflon rings requires a protector to prevent cutting or gouging them, and a sizing device.
 
−
It helps to heat the rings in hot water before installing so that they will stretch easier.
 
−
I use a piece of plastic (from a paint can cap) that is cut to size to install and size the rings. Leave it on until you are ready to install the direct drum.
 
−
 
−
Notice I left one sealing ring off, 2nd from top groove. This groove seperates the direct (3rd gear) and reverse feeds from each other. When dual feeding the directs (as done in this build), this sealing ring is not necessary. Dual feeding the directs on a Th400 will be covered in more depth in another section.
 
−
 
−
[[File:Center_support_rings.jpg]]
 
  
  

Revision as of 20:35, 28 January 2011

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