NO! Never reuse copper washers. Once they are smashed to seal the 1st time they can not be smashed farther to seal again. I will not disagree with Kenny on using RTV in place of them. But I would use new ones. The Ford part number is 373820S. But Parts stores have universal 3/8" brake banjo fitting copper washers that will work just fine.

 

 

You can sub RTV for a gasket. It's what I've done more than once. Although I prefer to use both on most things.

 

Ford listed the gasket 1957/79, then 1980/87: RTV

 

Use permatex black rtv oil resistant silicone and new copper washers which you can get at the hardware store. Shouldn't leak ever.

 

Yeah, those are the key words . . . . Oil Resistant RTV.

Although I always use 587 blue oil resistant RTV on my Dana 60s with a gasket, I only apply this same stuff on oil pans and trans pans when I install heat pads to the bottom pan surfaces as the pads never come loose even on the corners and stay dead flat !.

The only time I removed a 9 inch pumpkin was on my 70 Thunderbird when I swapped in a traction loc 2.80 ratio assembly to it, and only installed a new gasket back in June 1995, reinstalled the same washers and had no leakage problems with it.

I would imagine if no 'copper' washers that particular size were immediately available at a hardware store, you could sub for brass ones as they are a soft enough non ferrous metal as well although a little more durable than copper because the zinc mixture to make them.

I always had great luck with 9 inch Fords, changing oil on them is a breeze too by just lifting the rear axle on jackstands and pull the fill plug, let the engine idle and engage trans in reverse to spit out the old oil without removing the pumpkin.

 

I'd suggest "Right Stuff" from NAPA and no, never reuse copper sealing washers if new ones are available which they are. When I use a gasket in a situation like this I glue it to the diff so it won't slip. A very thin coat of some type of sealer isn't a bad idea but that is the purpose of the gasket itself.

 

I always just use Ultra RTV for "Gear oil". They actually just started offering it. I used to only use gaskets, but anymore RTV works just fine and no issues.
If you use a gasket, you can use gasket tack. It will glue the gasket to each surface keeping it from oozing out from too much RTV. That is usually the real problem with slipping gaskets.

 

I used to anneal the solid copper head gaskets on my drag bike. Heat to red hot and stick in a bucket of water.

 

Harbor Freight has a kit of copper washers really, really cheap...

 

GASKET PLUS RTV AND NEW COPPER WASHERS IMHO
for the little $ for new copper why risk a leak and having to do over ?