I have a 1970 Olds 442 automatic. I bought this car in 1977. The transmission blew up a few years later. I had it rebuilt & a shift kit added.
The transmission in there was not the original. The tag on the passenger side is stamped 77-AA-110531. The whole transmission is painted silver
so, there is no two-letter code on the tag. I'm guessing that the first two numbers are the year of manufacture. My question is: if this transmission
is from 1977 would it be the same as my original 1970 transmission? Would a 1977 trans be de-tuned to get better gas mileage at the expense
of performance. Would the governor be calibrated to shift sooner to save gas? Is there something that I could change to bring it back to the original
1970 specs & would it be worthwhile. The governor could be changed while still in the car. I have had issues with the transmission downshifting with
the electric kickdown.

 

The 77 means it’s a 77 model, I’m guessing out of a Cadillac.

The later th400s suffered the same penny pinching as everything else in GMs lineup. Unless someone has been into it before, it will almost certainly have plastic accumulator pistons, flimsy stamped steel pistons in the clutch packs, and more than likely thicker pistons for reduced clutch count.

If it’s being rebuilt, install the earlier aluminum pistons or the later 4l80 bonded pistons.

You can play around with governor calibration. Before even attempting gov calibration, make sure the kickdown solenoid is functioning. The trans will always tend to “short shift” at full throttle.


Install an accurate tach, it doesn’t need to be a permanent install. Get a spare gov to play with, install it. Take the car for a test drive, record full throttle shift points, both rpm and vehicle speed. If you want to fine tune the shift points, get a calibration kit from TCI, B&M, or TransGo. Follow the instructions, make one change at a time. Make sure you take detailed notes.

 

One thing is that trans won't have the attachment for the TCS (Transmission Controlled Spark) next to the kickdown prong. in 1970 there should be 2 prongs perpendicular to each other where the wires connect to it above the pan rail instead of 1.

Not that we use these things anymore.

 

"AA" is definitely a Cadillac trans. I don't have access to my trans code list at the moment, but I'm willing to bet that trans came from a Cadillac Seville with the EFI Olds 350 motor. In any case, it will be programmed for soft shifts and low upshift speeds. All TH400s have the same gear ratios of 2.48:1 first, 1.48:1 second, and 1:1 third.

 

I don't know what's inside the transmission after the rebuild, it has worked well for all of these years. I even pulled a boat trailer for a few years.
The only problem has been the kick down. I changed the solenoid years ago. I checked that it was getting power to the connector & could even hear a click inside.
If the piston inside the governor was stuck would that stop it from kicking down? I also changed the modulator to a new adjustable one. Whoever rebuilt it way back then transferred the two prong plug from the original tranny.
I have the TCS disconnected. I'm probably going to leave it alone. I have other projects that need more attention. Thanks everyone for the suggestions. I learned a lot here today.

 

The fact that the replacement trans has a two prong plug does not mean that the plug is connected internally or that there is even a pressure sensor in the valve body to connect to it. Of course, if the trans has been rebuilt, you have no idea what was done on the inside. I've swapped damaged cases during trans rebuilds myself. The case in my 1967 Delta is from a 1973 TH400 but I transferred all the 1967 internals, including the switch pitch functionality. (And yes, there is a special plug with an 0.040" orifice that needs to be installed in the replacement case to get the switch pitch to function)

 

It's sorely obvious that I don't know a lot about automatic transmissions. I know that the wire for the kick down connects to the plug
& connects to the solenoid inside the tranny. Also, the power reaches it when the pedal switch is activated. So, the solenoid works. The other wire is disconnected. My 1970 or 1977 Turbo 400 would not have a switch pitch converter, right? So, my car wouldn't need the special plug with .040 orifice. Thank you for the information.

 

Here is what a 1975 Cadillac big blocks factory WOT shifts looked like, center of screenshot.


Road Test Magazine May 1975 Cadillac Coupe Deville 500 CID.

Those shifts are 1000 rpm below what a 1970 442 would do. If a 77 version mated to a 350 is similar. Great for your engines health but the performance will be well below capability. Unless they modified the shift points back when transmission was rebuilt and shift kit was added.

Correct, unless someone added it after the fact. Factory switch pitch ended in 1967.