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Tech Editor's DeskProjects, papers, writings, thoughts, musings of our technical editor Joe Padavano. To begin with, he will be making threads and can approve posts to it if he wishes. This can be changed in the future if it does not work out well.
HEY TEDD
I thought I purchased a "stock" TH400
I pulled off the pan and this critter has been "modified"
I hoped that maybe a resident "expert" could tell me more by perusing the pictures
It was an automatic from the factory and now it is a manual transmission
Well glad to see a finishing nail holding the shift shaft, thought mine was the only one! thought I was looking at my picture. 72 TH400 in my 88. I replaced with a cotter pin, figured it was lost by previous mech and the nail was handy! Finishing nail?
Hydromatic used finishing nails to retain the manual shaft in the trans. They also used nails for the pivot shafts for the governor weights on the 400, 350, 700, 250, etc. GM spared no effort looking for ways to save money! I guess it was cheaper for them to buy nails instead of machining retaining pins or pivots.
The "finishing nail" is factory. Most of the TH400s I've had apart were the same. The only "modification" I see in the photos is that the kickdown solenoid wire is not connected to the pass-through terminal in the case.
That appears to be a home made manual valve body. The pipe plugs are blocking the govenor feed and return ports in the valve body. I’m guessing your also going to find a small hole drilled right above the return passage, the idea is to loop governor oil to the shift valves.
I’m curious to know what’s been done to the 2-3 accumulator and intermediate servo. I can see the pin for the accumulator piston has been removed. I can also see the vent hole in the 1-2 shift valvetrain is open, for the poor man homemade manual valve body to function that hole needs plugged, and the shift valve needs a vent ground into it.