Dos & don’ts - getting CV Joint bolts out

[PopsRacer]

I’m replacing the rear wheel bearings and axles on my 88 carrera. The 6 bolts that hold the inner CV joint to the transmission flange are really stuck. Since the flange is AL(?) I don’t want to hurt it.
I’ve read lots of ‘replace your CV joints” and “remove your stripped CV Joint Bolt” threads - but what are the good options for getting the bolts started?

* I have soaked them in penetrating oil for a full day so far and heated one up to cherry red a few times (heat, oil, wrench, repeat) but I have gotten nowhere so far.
* I did clean out the inside of it and made sure my 8mm hex key is good
* I have tried both hand and electric impact tools so far.

My guess is that heating the head of the bolt isn’t doing much since the threads are pretty far away. What is safe for the flange end of the bolts? TIA

[75 911s]

The transaxle flange is steel. Try to hit the backside of the thread with penetrating oil in between the flange and the trans.

Smack the head of each bolt straight on (lightly) with a flat hammer to break the rust loose.

Heat the flange a bit to make it bigger and then use an air impact. Make sure you are fully seated with the bit as you said. Wurth makes a cooling product that you can make the bolt smaller, or you could use carb cleaner. Not sure if that might make it brittle though.

Can also use a long breaker bar. That's what I usually use. Make sure your ebrake is on.

[88911coupe]

Clean inside the hole for the hex wrench thoroughly, mine had a LOT of grease and dirt so the wrench started to slip. Cleaning it gave more grip. Also use a GOOD wrench. I initially used one of my cheap hex's and they started to deform.