Editing TH400 rebuild tech

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=Rebuilding the T-400=

===Clearance in clutch packs:===

*Direct and forward clutch drums:

.050 to .080 in each drum works well with 5 frictions
Typically the thicker steel plates are used in the direct clutch drum. These can be mixed with thinner steels used in forward drum when setting clearance.
Try to maintain thicker steels in the direct clutch drum.  Thicker steels take the heat of shifting better.

*Intermediate clutch pack:

.040 to .060 clearance in the intermediate clutch with 3 frictions.
Always use a thicker snap ring .095 - .100 to retain the pressure plate

==Shift modifications==
*Valve body
insert photos and instructions

*Full manual shift modifications

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

There are two steel governor fluid tubes out the rear of the main valve body.  Remove these tubes.  Plug the holes in v-body. 3/8 x 16 tap and set screws work. Use liquid thread locking chemical

[[image:400v-body6.jpg]]
 
A new hole in the proper place needs to be drilled (.110) to loop the governor fluid. Check photos here for location

[[image:400v-body-7.JPG]]


==Jakeshoe rebuild tech:==
This post is meant to help those who wish to rebuild their own transmission, however it is not meant to replace a quality rebuild manual.
I recommend using an ATSG rebuild manual, HP Books "How to Rebuild and Modify the TH400", and this post for those new to transmissions.

I will be covering some modifications that are not usually required but good to do.

After you have disassembled your trans and cleaned the mostly bare case, I recommend you change the shift shaft seal, kick down connector o-ring, and rear case bushing.
Pictured here is a tool that allows removing the shift shaft seal without removal of the parking linkage. It is relatively inexpensive and can be used without pan removal (in the car).

Be sure to lube the seal before re-installing, and take care not to cut it on the edges of the shifter shaft.
If you do not have the tool or wish to buy it, now is DEFINITELY the time to change the seal, it requires removal of the linkage. You want to do this before you have the trans internals assembled. If you drop the "nail" in the case, or anything else, it is very frustrating later on to disassemble.


A universal cam bearing tool can be used to replace many bushings in the various automatics. It will not do very small bushings. Pictured here driving the bushing out towards the front.

A TH400 and 4L80-E 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, red loctite in place, and staked in place.



[[Category:Transmission]]
[[Category:Undeveloped articles]]