Loctite 29513 Blue 246 High Temperature Medium Strength Thread Locker, 450 degrees F Maximum Temperature, 10 mL Bottle

Great to use in transmission and differential plugs.

Use this if you are fastening nuts/bolts/studs that will be subjected to heat. It is heat resistant to around 400-450 degrees, F. I called Loctites tech support number ( I got it from a fastener store where I live) and asked which product is good for these situations, and they told me to buy this product. I was using it on studs that hold headers to the head on a water cooled motorcycle. The parts are removable, but you will need to heat the fastener with a heat gun before removal.