Looking for a few opinions on replacing a rear freeze plug in my 1968 Camaro with a 350 engine and TH350. Is it easier to remove transmission or remove motor mounts and jack motor up? Can I even get to rear plugs by just removing transmission? Not exactly sure which freeze plug it is, but almost posotive it is on back of motor. Water dripping down between bellhousing and flywheel. Planning on using a rubber expansion plug, which I have used before with no problems. Main question I have is, how am I going to get the old one out without removing the motor?? Car is a convertible so I have the "X" brace under rear of trans. Also, this will be done on my back with front of car jacked up. Thanks in advance for any replies.

Easier to pull trans, block motor up at pan, replace freeze plug with brass , 1 5/8" , takes two there and while you are at it, replace the others in block, sooner or later they will go unless you already have done this.
I have always done this on my back . I say brass plugs as rubber will tend to rot later. Do it right first time. Put a smear of permatex 1 on the plug and tap in.

X2 on doing the other plugs (and brass instead of rubber), surely they are next to fail.

Don't worry about finding the leaking plug, you'll know it when you see it.

Ok, looks like I am fixing to start removing the trans. I'm assuming that I will have room to knock the brass freeze plug in if I remove the transmission? I have replaced all the freeze plugs except the back ones within the last year, so I should be good on all of those. I just hope I have room to swing a hammer to knock the old one out. A couple of the other ones were a PITA. I had to drive a screwdriver through one and pushed it into the block but was able to fish it back out. I will update soon as I get trans out. Thanks for the advice.

That's the way I do it, sometimes the hole will cave in an a long driver or screw driver will pop them out. You can also grab them on the lip with a pair of channel locks, if they fall some, but they do come out.

Don't forget to remove your distributor (not just the cap) so the back of the engine sags and gives you the best angle for this repair.

Got the transmission out on the ground with a jack and 2 x 4 under the oil pan of the motor. I did remove the distributor, but I didn't think I would have to remove the flywheel but it looks like I will. Are the flywheels juist bolted on or pressed on? The reason I ask is because when I took the old motor out some time ago, I went to remove the flywheel and could not get it off. It was like it was put over the shaft and then had a lip and I tried and tried and could not pry it off. Thankfully the new replacement motor already had the flywheel on it. Has anyone experienced that? I hope this flywheel is not like that. Fixing to go unbolt it and keep my fingers crossed.

Stuck flywheel is normal, ever so in your area. Put some PB blaster, or rust dissolver and let it saturate, maybe tap it with a block of wood, it will come up when you least expect it.

It may be aligned with a dowel hole so you could try to rotate, goferit.

Definately passenger side rear freeze plug. Has a pin hole right in the middle of it skeeting water out. Still working on removing flywheel. Got all the bolts out but 2 and my impact won't budge them with 150psi. Looks like I'm going to have to go to a wrench with a cheeter pipe. What's the best way to keep the engine from turning over? I have the trans and driveshaft out. I'm leary of putting something in a spark plug hole to stop the piston. Thanks for all the advice guys. This forum is invaluable.

Put some penetrating oil on that bolt , it should pop with an air impact, use 6 point impact socket to keep from rounding bolt head off.
There is a fly wheel wrench , to turn the flywheel or hold it if you have to put a long 18" or so breakover on it. Some auto store have a loaner tool program, I know O'reilly does.
I have done this in my very early days, I pulled crank pulleys off , and put a small pipe wrench between the spokes and allow to be backed up at the front cross member. I did this out of desperation , young and dumb. But it worked, I had no major tool but a small snap on set.
Also another desperate act, Your flex plate should have round holes in it, you could put a long 1/2" extension that will or should hit somewhere near the starter area.
Put some penetrating oil first. Might even put a little oil in that impact inlet, that will give you a little hammer boost.
Be careful not to rock the car on jacks, pull down wards, not sideways. I think those bolts are either 5/8 or 11/16" socket size. Put a little oil on those bolts going back together.
Work safe.

Use a brass plug. Never use a rubber plug, especially there. You will have to do it all over again. Rubber plugs are just for getting you home. I put brass plugs in every engine I install. I even remove the steel plugs in brand new crate engines before I install them. It is crazy not to. Steel plugs look on the outside, and then , bam you have got a leak. A little black RTV and a socket that will fill the center of the plug , and then just tap it in. Sometimes a socket and a short extension will make life a little easier. Brass yes , steel no, rubber hell no! Leave rubber for the tires, it has no place in a freeze plug.

Remove a sparkplug and thread some fine rope into the hole so that it interferes with the piston rising. This will keep the engine from turning so you can break free your stuck bolts.

I have herd of the rope trick. Never done it because there is way too many other safer ways to do it. A flywheel tool works great, or just wedging a hole in the flywheel like mentioned before. If you do not have the cylinder on the compression stroke , you risk bending some valves. Not a good idea for a newbie.

Thought about that too, but its like compressing water. You get a shorter rod and maybe some bearing damage?
Surely 150# air on a 1/2" drive impact will loosen it .

Just wondered if he removed pushrods and aired up one cly? Surely head gasket would hold.

Some great advice here fellas. I finally got the bolts loose by putting a large screwdriver through one of the holes in the flywheel and wedging it against the block close to where the starter mounts. My 1/2" air impact with 150 psi wouldn't break them loose, but my long 11/16 wrench and a cheeter pipe did. Used a little PB Blaster and pried just a little bit on the flywheel and it popped right off. Good advice on leaving a couple of bolts in for when it pops off. Probably saved me some skin. Ended up pushing freeze plug into block but luckily was able to fish it back out and pull through the hole. On my way to parts store now to buy a BRASS freeze plug. I have heard mixed opinions on using a little RTV on plug. Sure don't want to do this again anytime soon.