Changing fluids in trans and diff.
replacing the plugs and the large drain plug on trans & lower diff is M18 with 1.5 thread size.
these work great on drain plug for diff and larger trans plug and will not strip like the OEM 24mm head M18 bolt. The magnet is also 10x stronger.
https://goldplug.com/shop/mp10/

But here is the issue.
the fill plug on Diff had a M18 in it that was sealed up but the threads seem stripped by the local jiffy lube years and years ago ( over 10years)
I only found out when trying to put the fill plug back in, and it just kept turning
So it does not work with the M18 bolt with a 19mm head.

What is the thread size of the Diff fill plug ?
I am wondering if the shop used the wrong bolt of M18 over a NPT 1/2 . like the ones in on the S5 TII transmission fill plugs.
If it is M18 and stripped I will likely go NPT 1/2 and tap it but wondering if I have to drop the diff to tap the Diff top fill plug?

 

Problem solved. Tapped to 1/2 NPT while on the car and no need to drop the sub frame or diff.
Make sure to clean out the shaving from the tapping.

Here are the tools and new plugs.
Now all fill plugs are 1/2 NPT.


transmission fill plug, 1/2 NPT tap (3" long) wit 15mm ratching wrench, 14mm wrench, new hex 1/2 NPT plug with hex wrench, old M18 plug

old stripped M18 threads