: th400 rebuild



72HearseGuy
05-02-13, 07:14 PM
Hey guys, long time no post. I'm planning on rebuilding the 472 in my 72 hearse next spring. I figured id service the transmission too. Its not too bad, sometimes it shifts a little hard. No major issues though. What kind of kit should I buy, and what video/manual do you suggest. Any tips? Trying to get everything ready so I'm ready come rebuild time.

Roadmaster75
05-03-13, 11:23 AM
hard shifting could be one of two items that only require external serving/troubleshooting:

Governor set up and adjustment (see shop manual)
or,
simple vacuum modulator adjustment or replacement (cheap)
Also, ensure the vacuum line to the modulator is getting full vacuum from the manifold.
This means inspect the little rubber hose and connections to ensure there are no leaks.
With these items checked and a fresh filter/fluid change I'm guessing you
have a perfectly good trans without a teardown.
my 2 cents
mike

The Ape Man
05-03-13, 12:39 PM
Hard shifting can be a good thing. A poor vacuum signal should be ruled out first as mentioned. If it were mine I'd change the pump seal while the engine is out. Maybe the driveshaft seal too if it leaks, change filter and fluid and enjoy. The engine rebuild is enough stuff at one time.

Maybe find another transmission and rebuild it in your spare time.

BRUCE ROE
05-04-13, 12:17 AM
If your trans is original, it is way overdue for a new set of soft parts (rubber seals). A blown piston seal
could BURN UP a perfectly good trans. Good news, it only costs $30. I'd take it apart & check damage before
deciding. A set of clutches will double the price, except yours (like my 70) likely has an extra plate in the
direct clutch, which I've never seen in a kit yet. Full kit has steels double the price again, I NEVER replace
steels or other hard parts, if they show no wear. Esp DON'T replace the 3 wavy plates with flat, if you
want it to shift like new. Get a new set of torringtons, I replace plastic thrust washers with metal.

There are a few tools that greatly help the rebuild; I learned from the factory service manual. Converted
my 70 to a switch pitch, so smooth. Bruce Roe

GM_Parts_Guy
05-31-13, 11:39 PM
If your dead set on doing a rebuild (i look at it like your right there with the motor rebuild would not be much extra to do the trans and you know you have a fresh trans mated to the fresh motor) Trans-star and TCI Trans both make very good kits. I've used both.