Can anyone tell me how to remove the transmission from an engine that is seized?
Every article I've seen says to remove the bolts from the torque converter first, but I'm unable to turn the fly wheel on my '66 S type.
Any suggestions

 

If the engine is seized why mess about trying to separate the two whilst in the car and just pull both out at the same time. I have removed my Auto trans from my 1967 S Type (I say I, but I had a garage do it for me as they were rebuilding the trans) and access was made via the vent holes in the bottom of the bell housing to separate the torque converter as you said but if the engine does not rotate getting to the top bolts is going to be very hard.
Other than that what is seizing the engine. Rings, big ends, something else snapped? Can the engine be freed up by soaking the bores with oil? Try removing the radiator and then putting a socket on the front pulley bolt with a long extension bar. Place a hydraulic jack under the handle of the extension bar and jack it up so it is under pressure and leave it overnight having soaked the bores in oil. Every hour or so just give the jack a pump to keep the pressure on the handle. Time is your friend and eventually the engine should start to move. Might take a couple of days if this is just the pistons rusted into the bores.

 

A 66 S-Type should have the DG Gearbox, to remove the transmission just unbolt the bolts around the bell housing and pull the gearbox off the torque converter. There will likely be some oil loss when doing this.

Once done you will then be able to access all the bolts on the torque converter to remove it, I had to do exactly the same on my 1967 MK2 with a DG Gearbox.

One thing to mention, the DG gearbox has a metal tube/piece that fits into the input on the gearbox, when you take it out the piece might come out with the box, it might stay in the torque converte or it might drop out. Just make sure when you put the gearbox back on you remember to refit this.

If your in the UK and need any bits for the gearbox I can highly recommend Graham Whitehouse Autos https://www.gwautos.com/, they have supplied bits for all three of the ones i've rebuilt and are really helpful.

 

Another vote for Graham Whitehouse - he supplied a modulator and other bits for my GM 400. The shift is less lazy, but not jerky.

 

Also another vote for the advice from Cass. Take the fan belt off as the water pump is probably solid. If the crank begins to turn, take it very gently as valves may be stuck as well.