1968 AMX390 M12

I have the M12 automatic out of my 68AMX. Tomorrow I'm hoping to pick up the rebuilt heads. In short order the rebuilt engine should be re-assembled and installed. The M12 transmission only has 21,000 miles on it since it was rebuilt in 1981, and new torque convertor. What do you recommend be done to it before I reinstall it?

When was the last time the car was driven? Did it work good at that time?

My opinion, it was done 33 years ago...personally I would take it in and get it looked over and new seals installed or if your good with transmissions do it yourself. It's easier to do it now than later and then you won't be left stranded somewhere and forced to use a shop you wouldn't normally.

Other than front and rear seals you only have o-rings in the shift lever shaft that I can remember. May as well replace them. The pan has to come off but that's all. There are o-rings in the servos that could dry up and shrink, and some in the valve body. Wouldn't hurt to replace the servo seals (they come out easily) and take the VB apart an clean it real good. Make sure you have a service manual before taking the VB apart though! There's not much to it, just have to keep things clean. There are a couple little check balls that can fall out when disassembling though, and you have to know where to put them back in.

All good suggestions. Here's a couple more that you need to do before the trans is in the car. I have a LOT of experience with these trans.

Downshift/passing gear solenoid bulkhead fitting O-ring. It is a on a plastic connector that goes through the side of the case. It pushes out from the inside. Add a little silicone to the seal and push it back in.

Shift shaft seals, They require valve body removal.

Servo seals, hey, they are in your hands to get the valve off anyways.

Band and auto adjuster settings. The top one is very hard to do in the car.

Don't worry about the clutch pack seals as they are deep inside and would not be very dried out in a used tranny just from years. A low miles rebuild should still be fine.

You have to start somewhere! Take a look at the TSM. The valve body drops right out with 4-5 screws. There are 2-3 screws that hold the two halves of the VB together. Take those out last, and on a lint-free cloth (old bed sheet works, towel doesn't!). There is one or two check balls that should come out, the TSM shows where to put it (them) back. The servos are even easier -- just a bolt or two holding them in. None of this is much harder than taking the filter out. These are pretty simple transmissions. Back in the early 80s I hadn't done as much as you have, and I pulled one apart and rebuilt it with no issues. If you have the TSM it's not hard at all. If you've ever done some engine work (rebuilt an engine?) it's a good one to cut your teeth on.