TH400 rebuild tech

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m (moved T-400 Rebuild tech to T-400 rebuild tech)

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==Rebuilding the ~~TH400~~==

+

==Rebuilding the T-400==

===Clearance in clutch packs:===

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===Full manual shift modifications===

+

FULL manual shifts means just that. You must move the shifter for every shift up or down. NO Automatic shifts.

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==Valve body mods, automatic shifts==

−

The ~~TH400~~ has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage.

+

The T-400 has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage.

You can eliminate this feature by performing the following modifications to the valve body.

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−

==~~TH400~~ transmission rebuild tech==

+

==T-400 transmission rebuild tech==

'''NOTE:'''

−

*This information and photos are meant to help those who wish to rebuild their own transmission, however this is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is an ATSG rebuild manual, HP Books "How to Rebuild and Modify the ~~TH400~~", and this post for those new to transmissions.

+

*This information and photos are meant to help those who wish to rebuild their own transmission, however this is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is an ATSG rebuild manual, HP Books "How to Rebuild and Modify the T-400", and this post for those new to transmissions.

The article by jakeshoe can be seen in the Hotrodders forum thread [http://www.hotrodders.com/forum/t-400-build-tips-photos-145318.html T-400 Build Tips With Photos]. Also covered are some modifications that are not usually required, but are still good to do.

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[[file:Rearbushingdriver.jpg]]

−

A ~~TH400~~ and 4L80E used in heavy towing will sometimes cause the rear bushing to "walk" to the rear, ruining the governor gear. There is a "fix" bushing for this that has a thrust surface on the front that prevents the bushing from walking.

+

A T-400 and 4L80E used in heavy towing will sometimes cause the rear bushing to "walk" to the rear, ruining the governor gear. There is a "fix" bushing for this that has a thrust surface on the front that prevents the bushing from walking.

Use a stock bushing with red loctite and staked in place.

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If you plan on using a rear torrington-type bearing you want to place the bushing ever so slightly protruding to the front, so that it will locate the bearing.

−

I use a ~~TH350~~ pump - direct drum bearing from a later style ~~TH350~~. These can be ordered new (preferred). This torrington bearing replaces the stock thrust washer and rear selective tang washer in the ~~TH400~~.

+

I use a T-350 pump - direct drum bearing from a later style T-350. These can be ordered new (preferred). This torrington bearing replaces the stock thrust washer and rear selective tang washer in the T-400.

Pictured here, bearing is at the top:

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−

You set rear end play using ~~TH350~~ pump shims as pictured on the left here:

+

You set rear end play using T-350 pump shims as pictured on the left here:

[[file:Rear-thrustshim.jpg]]

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[[file:Rear-bearing-measure.jpg]]

−

It is best to adjust rear endplay on the tight side. On a ~~TH400~~ (unless it has straight cut planetary gears) the planets will try to thrust load against the case bearing and the center support.

+

It is best to adjust rear endplay on the tight side. On a T-400 (unless it has straight cut planetary gears) the planets will try to thrust load against the case bearing and the center support.

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[[file:Seal_rings_t-400.jpg]]

−

*Cast iron is what most kits will contain, and what was used stock in most ~~TH400~~'s. 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.

+

*Cast iron is what most kits will contain, and what was used stock in most T-400's. 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.

−

*Scarf cut teflon was used on later model ~~TH400~~'s.

+

*Scarf cut teflon was used on later model T-400's.

*Solid teflon is used on 4L80s and is interchangeable. I prefer solid teflon, although it is the most time consuming type. 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 separates 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.

+

Notice I left one sealing ring off, 2nd from top groove. This groove separates 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 T-400 will be covered in more depth in another section.

[[File:Center_support_rings.jpg]]

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===Sprag design comparison===

−

The next picture shows a common roller clutch style drum and a roller clutch on the left, most ~~TH400~~'s will use this style drum. Early units, pre-'71, will have the smooth inner race style drum on the right. 4L80E's also use the "early" style drum and an actual sprag. The stock 16 element sprag is in the center, with the 34 element on the right.

+

The next picture shows a common roller clutch style drum and a roller clutch on the left, most T-400's will use this style drum. Early units, pre-'71, will have the smooth inner race style drum on the right. 4L80E's also use the "early" style drum and an actual sprag. The stock 16 element sprag is in the center, with the 34 element on the right.

[[file:Sprag-drum-compare.jpg]]

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===Spiro loc retainer===

+

This is a picture of an upgrade for high RPM applications, it is a spiro lock type retainer instead of a regular snap ring. The regular snap rings will release due to centrifugal forces at high RPM. This fits on the direct drum plate that covers the sprag.

+

The 4L80E direct drum uses a sprag race that is .045 to .050 wider than the T-400 sprag race. If you acquire a 4L80E direct drum be sure to have the correct race too.

[[file:Spirolock.jpg]]

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==Resources==

*[http://www.tpub.com/content/trucks1.25ton/TM-9-2320-280-34/ Army Technical Manual] with specific step by step instructions for basic rebuild. Halfway down the page, look for 3L80 links.

−

*[http://www.nastyz28.com/forum/showthread.php?t=131600 ~~TH400~~ Rebuild Tips and Tricks] by jakeshoe at Nasty Z28.com from 2006.

+

*[http://www.nastyz28.com/forum/showthread.php?t=131600 T-400 Rebuild Tips and Tricks] by jakeshoe at Nasty Z28.com from 2006.

[[Category:Transmission]]

[[Category:good articles]]

TH400 rebuild tech

Revision as of 20:47, 22 March 2012

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@@ Line 1: / Line 1: @@
 {{youcanedit}}
-==Rebuilding the TH400==
+==Rebuilding the T-400==
 ===Clearance in clutch packs:===
@@ Line 18: / Line 18: @@
 ===Full manual shift modifications===
 FULL manual shifts means just that. You must move the shifter for every shift up or down. NO Automatic shifts.
@@ Line 94: / Line 95: @@
 ==Valve body mods, automatic shifts==
-The TH400 has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage.
+The T-400 has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage.
 You can eliminate this feature by performing the following modifications to the valve body.
@@ Line 127: / Line 128: @@
-==TH400 transmission rebuild tech==
+==T-400 transmission rebuild tech==
 '''NOTE:'''
-*This information and photos are meant to help those who wish to rebuild their own transmission, however this is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is an ATSG rebuild manual, HP Books "How to Rebuild and Modify the TH400", and this post for those new to transmissions.
+*This information and photos are meant to help those who wish to rebuild their own transmission, however this is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is an ATSG rebuild manual, HP Books "How to Rebuild and Modify the T-400", and this post for those new to transmissions.
 The article by jakeshoe can be seen in the Hotrodders forum thread [http://www.hotrodders.com/forum/t-400-build-tips-photos-145318.html T-400 Build Tips With Photos]. Also covered are some modifications that are not usually required, but are still good to do.
@@ Line 150: / Line 151: @@
 [[file:Rearbushingdriver.jpg]]
-A TH400 and 4L80E used in heavy towing will sometimes cause the rear bushing to "walk" to the rear, ruining the governor gear. There is a "fix" bushing for this that has a thrust surface on the front that prevents the bushing from walking.
+A T-400 and 4L80E used in heavy towing will sometimes cause the rear bushing to "walk" to the rear, ruining the governor gear. There is a "fix" bushing for this that has a thrust surface on the front that prevents the bushing from walking.
 Use a stock bushing with red loctite and staked in place.
@@ Line 156: / Line 157: @@
 If you plan on using a rear torrington-type bearing you want to place the bushing ever so slightly protruding to the front, so that it will locate the bearing.
-I use a TH350 pump - direct drum bearing from a later style TH350. These can be ordered new (preferred).  This torrington bearing replaces the stock thrust washer and rear selective tang washer in the TH400.
+I use a T-350 pump - direct drum bearing from a later style T-350. These can be ordered new (preferred).  This torrington bearing replaces the stock thrust washer and rear selective tang washer in the T-400.
 Pictured here, bearing is at the top:
@@ Line 162: / Line 163: @@
-You set rear end play using TH350 pump shims as pictured on the left here:
+You set rear end play using T-350 pump shims as pictured on the left here:
 [[file:Rear-thrustshim.jpg]]
@@ Line 171: / Line 172: @@
 [[file:Rear-bearing-measure.jpg]]
-It is best to adjust rear endplay on the tight side. On a TH400 (unless it has straight cut planetary gears) the planets will try to thrust load against the case bearing and the center support.
+It is best to adjust rear endplay on the tight side. On a T-400 (unless it has straight cut planetary gears) the planets will try to thrust load against the case bearing and the center support.
@@ Line 205: / Line 206: @@
 [[file:Seal_rings_t-400.jpg]]
-*Cast iron is what most kits will contain, and what was used stock in most TH400's. 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.
+*Cast iron is what most kits will contain, and what was used stock in most T-400's. 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.
-*Scarf cut teflon was used on later model TH400's.
+*Scarf cut teflon was used on later model T-400's.
 *Solid teflon is used on 4L80s and is interchangeable. I prefer solid teflon, although it is the most time consuming type. 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 separates 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.
+Notice I left one sealing ring off, 2nd from top groove. This groove separates 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 T-400 will be covered in more depth in another section.
 [[File:Center_support_rings.jpg]]
@@ Line 278: / Line 279: @@
 ===Sprag design comparison===
-The next picture shows a common roller clutch style drum and a roller clutch on the left, most TH400's will use this style drum. Early units, pre-'71, will have the smooth inner race style drum on the right. 4L80E's also use the "early" style drum and an actual sprag. The stock 16 element sprag is in the center, with the 34 element on the right.
+The next picture shows a common roller clutch style drum and a roller clutch on the left, most T-400's will use this style drum. Early units, pre-'71, will have the smooth inner race style drum on the right. 4L80E's also use the "early" style drum and an actual sprag. The stock 16 element sprag is in the center, with the 34 element on the right.
 [[file:Sprag-drum-compare.jpg]]
@@ Line 284: / Line 285: @@
 ===Spiro loc retainer===
 This is a picture of an upgrade for high RPM applications, it is a spiro lock type retainer instead of a regular snap ring. The regular snap rings will release due to centrifugal forces at high RPM. This fits on the direct drum plate that covers the sprag.
+The 4L80E direct drum uses a sprag race that is .045 to .050 wider than the T-400 sprag race. If you acquire a 4L80E direct drum be sure to have the correct race too.
 [[file:Spirolock.jpg]]
@@ Line 338: / Line 342: @@
 ==Resources==
 *[http://www.tpub.com/content/trucks1.25ton/TM-9-2320-280-34/ Army Technical Manual] with specific step by step instructions for basic rebuild. Halfway down the page, look for 3L80 links.
-*[http://www.nastyz28.com/forum/showthread.php?t=131600 TH400 Rebuild Tips and Tricks] by jakeshoe at Nasty Z28.com from 2006.
+*[http://www.nastyz28.com/forum/showthread.php?t=131600 T-400 Rebuild Tips and Tricks] by jakeshoe at Nasty Z28.com from 2006.
 [[Category:Transmission]]
 [[Category:good articles]]