Diff Cover bolt size

I am planning on replacing my diff fluid this weekend and it is the first time I have done it. Since I am on a mission to remove anything that can rust on my 91 I would like to replace the cover bolts on my 30 Front and 35 Rear w/ stainless. I was wondering if anyone knew what length/thread for the bolts. Thanks

Don't worrry about using stainless. The bolts on diffs virtually NEVER rust solid into their bores.

If you REALLY want stainless, take ONE of the TOP bolts out, and go to the hardware store. It's safe to drive a short distance with ONE bolt missing from the top.

They are 5/16" coarse thread....3/4" works well I believe.

For a cool look paint your diff cover a nice fresh black.

Install stainless bolts with lock washers.

Actually they are the metric size that is very close to 5/16-18. The markings on the head of the fastener will usually reveal what grade, be it metric or standard.

Right, it's a metric size. I can get the exact size tonight when I get home, as I replaced mine with longer bolts when I put on a rock ring.

I would not, however, recommend stainless bolts. Stainless steel is more brittle than standard carbon steel, so they are worse in that sense, not better. And, as AZ Jeff said, these bolts do not get rusty, so there is no advantage at all to swapping them for stainless. If you're just doing it for looks get some chromed bolts.

Chrome plating also embrittles the metal. If it's just for looks, use the standard carbon steel bolts and get stainless caps to cover the bolt heads.

"Chrome plating also embrittles the metal." I didn't know that. See, you learn something new every day.

The size, by the way, is m8. Be sure to use plenty of lock-tite or some other sealer or the bolts will seep diff oil.