Hi all,

Can any of you confirm what the size of the nut is that goes on the studs at the rear of the oil pan that are also integral with the rear main seal?

I found this description for item 423 "Nut, hex 5/16-18x.25 286m por (acdelco #12338130)" at https://nemigaparts.com/cat_spares/e...t/00/tx00-046/

I also found this link for the part number: https://www.wholesalegmpartsonline.c.../12338130.html

I'm thinking I'd like to install some additional nylok nuts so to secure the OEM ones in place after I torque them down. I had an oil leak seem to go away after I re-torqued them last summer.

I was surprised to see it listed as non-metric.

 

I can’t say for sure on the size and pitch of the fastener but what size socket was required to tighten? Also not uncommon for gaskets to compress over time just from heating and cooling cycles. Oil pan and valve covers are notorious for this.
Brad