mark79,80

I am replacing the differential plug on a 1980 that I may have damaged by over tightening. I used ATF fluid on a black iron plug to act as a chaser to straighten any damaged threads in the differential case. I can thread the black iron plug in 4 revolutions before the ratchet starts exceeding about 10 foot pounds.

Ready to install the new aluminum plug. It has about 7 revolutions of thread, so 4 is only partially threaded. Which would be better to use: Permatex Aviation Sealer or Anti-seize? I thought anti-seize may act as a lubricant and allow the plug to be tightened further, but a sealer may stop fluid seepage even though less threads can be driven in the case.

AzMotorhead

I'd use the sealer. Not sure but I believe the plug is a NPT thread so it should tighten as is threads in before it bottoms.
Use a new plug and put thread sealer on the threads

Brcmpbl

I use thread sealer, just a little.

You don't need to tighten it too much - it's common for several threads on the plug to still be showing with the plug seated sufficiently.

mark79,80

Threads are NPT

Street Rat

Use sealer on the aluminum plug. If it was a steel or brass plug I'd use anti-seize.

BlackC3vette

I just went thru this not long ago. The AIM calls for a 9985253 sealant which converts over to a Permatex High Temp Thread Sealant, #59214. The first auto store I stopped at had it.

The plug is NPT and does not thread all the way in and bottom out. The AIM listed 10 to 15 ft lbs for the tightening.

http://www.itwpf.com.au/permatex/pdfs/approvals/7.pdf
https://www.permatex.com/products/th...hread-sealant/

mark79,80

For anyone else in need of a new filler plug. The original GM no. Is 14024358. I was able to purchase a NOS replacement. It is coated with a type of paint where as the original is bare aluminum. The same part was used on some C4's as there is a thread on the topic. That same thread also lists other part numbers that can be used: Dana/Spicer 39527, GM 4626710 and Mopar 4626710AB. I also found much easier access to the plug by removing the spare tire tub. This enabled viewing and cleaning the threads in the differential case and enabled using a torque wrench.