1961 differential drain plug gasket
 

My 61 GMC diff drain plug won't stop leaking. I tried different gaskets, copper washers and made my own plastic washers. I just obtained a 60 or 61 GMC parts truck and removed the plug to find the gaskets is deteriorated but it looks like it's made of cork. Anyone have a problem like this?

Re: 1961 differential drain plug gasket
 

I think they were leather.
I'd find a Teflon washer.

Re: 1961 differential drain plug gasket
 

The seals were fiber- you say its the drain plug leaking but it looks like a fill plug in the cover to me. Here is one I bought for mine, there are suppliers that sell the fiber gasket separately.
https://www.classicparts.com/1934-72...ctinfo/93-223/

Re: 1961 differential drain plug gasket
 

Maybe some thread sealant on male threads along with the gasket? Teflon or rector seal thread sealant?

Re: 1961 differential drain plug gasket
 

I asked my son to take the drain plug out of the parts truck but it looks like the fill plug in the picture. Next I'll try Teflon tape. This is getting annoying lol

Re: 1961 differential drain plug gasket
 

Wow, good timing on this. Was just changing oil in my HO and discovered that some old parts house fill plugs I bought years ago were flat on the sealing surface but an original I had was tapered to match the taper on the diff cover. That got me wondering what the proper gasket was. Funny how after all these years I never noticed the difference.
Thanks for the info on the Classic part. Couldn’t tell by the picture on their site if it is tapered or flat on the back. Also is the plug the same for 1/2 and 3/4 ton rears?
Thanks
Tom

Re: 1961 differential drain plug gasket
 

Did you ever find what you were looking for? I actually have some NOS fill plug gaskets which I'll be posting in the parts board here shortly. They are a flat fiber gasket, GM # 3714775.