The Stovebolt Site Forums The Shop Area Driveline 3100 rear diff gasket question

I'm getting ready to change the rear differential gasket and oil in my '51 3100, but when I checked at NAPA and classic parts, both are telling me there are two different gaskets available. Both 10 bolt, both the correct diameter. Does anybody know what the difference is between the two, and does it matter which you use? Does one not fit the other's application? Is one cork and the other the other silicone? I'm not taking it off till I hear from someone. NAPA will have one of them Monday (said the other might take a week). Thanks.

About 30 years ago I couldn't find the right gasket and didn't have enough material to make one, so I cleaned both surfaces well and applied RTV sealant (silicone some would say) around the cover about 3/16 thick in 2 lines spaced about 1/4" apart, making circles around each bolt hole. Let it sit there for 10 or 15 minutes...followed the directions on the tube...and then installed the cover. It never leaked a drop after that and the tube of sealer cost me about $6 or $7. Good luck.

Here is the one I ordered from Classic Parts (part 93-911) last year and if fit perfectly, on my ‘52 3100, with the original torque tube rear. https://www.classicparts.com/1933-63-Rear-End-Cover-Gasket-10-Bolt/productinfo/93%2D911/

Thanks, fellas! Jon, I thought about doing that if all else failed. And thanks for the number Phil.

The confusion at NAPA is probably because there's a slightly different gasket for the differential to housing joint and another for the rear cover. I replaced both of mine when I put the chassis back together (and put sealant on the wrong one as I was putting them on ).
Got mine from The Filling Station their PN's FS-54 for the cover gasket and FS-54A for the differential gasket. They were both Fel-Pro brand, but I don't have those PN's.

The one that mounts the center section to the housing is real thin paper. The one for the cover is cork. You want the cork one if you are just pulling the cover.
George

Thank you very much! This helps. Seems they would specify the different location of each gasket, at least at classic parts, anyway. But this is what I needed. Napa said the gasket will be in today, so I'll see what they send.

This product works better than RTV for making flange gaskets for things like differential covers. It's a thick liquid that's applied and spread into an even layer with a putty knife prior to bolting the parts together. We used it frequently when installing differential center sections on big rigs.

https://www.permatex.com/products/g...tex-anaerobic-gasket-maker/?locale=en_us

It beats trying to keep a bunch of gaskets in stock.
Jerry

Thanks, Jerry! I'm about to try that. I had NAPA order a gasket for me Friday, and they said it would be in Monday. Mind you, the NAPA that I use is 8 miles away in Farmington, MO, and when I went down there to pick it up on Monday, they handed me a cardboard box. I wanted to check it before I bought it, and that's when I noticed one end was open. Then I saw that it was empty. I laughed and told the guy it was the wrong one and held the box open for him to see. His eyes got big and he went back and showed one of the other guys, and they both shook their heads. He said he was sorry, and couldn't believe the warehouse sent it without checking it, and told me he'd have the right one in today after 1. Stopped in there today on the way back from our property down south and picked it up and a couple of quarts of 80-90 oil for the job. When I got home and started to put it in the cab of the '51 and read the label, and it said it was for 3/4 or 1 ton trucks. Called them to tell them they sent the wrong one, and the guy asked if I had the old gasket. I said no, I'm not taking it apart until I've got everything ready to go. He told me to take it apart and bring the old gasket down there and they'd make sure they got the right one next time. The only thing I'm going to go back for is to get my money back. I'll either order it from Classic parts, which means it will be double the price and a week's wait, or do what you said about using permatex's aerated sealer. I mean, I like those guys down there, and 8 miles isn't that far, but it would be my 4th trip down by the time they finally get it in, and although I'm retired, I DO have other things to do. So, anyway, I'll get some of the sealer you mentioned when I take the gasket back and try it that way. All this may not even be necessary, but I've had the truck almost 10 years and have never popped the cover or changed the oil in it, so I'm going to do it 'for the fun of it!" (That's what I tell myself, anyway.) Thanks again. I'll let you know how it goes, bud.

Pick up a make a gasket kit there about 10 bucks it has 2 sheets of cork and 2 sheets of a paper like product. Make your own gasket Napa doesn’t have the cork gaskets and can’t get them they are not manufactured anymore. I made my own and no more leaks

Will do! Thanks for the tip.

That empty box, a ball peen hammer, and an X-Acto knife would have made almost as good a gasket as the one that got lost in shipment. I can't count the number of flat thin gaskets I've made from the cardboard backing of a legal pad, or even a magazine cover. Just trace around the outside of the part, mark the bolt holes, and whittle one out!
Jerry

Another option is a Pendaflex folder file. That material is not as easy to cut (much tougher), but it will work for all sorts of gaskets.

Just got back from returning the gasket to NAPA. While i was there i bought a 50ml tube of anaerobic permatex, and i plan on doing this today, if the rain doesn't appear. This wasn't a big necessity, and with all the wrong items shipped to the store, I'm done with trying to get a gasket for now. The guy behind the counter, who i know well, asked if they ordered the right one. I told him no, that the guy on the phone said to bring the old gasket in, then told him i've made enough trips and wasted enough time on something that isn't really needed anyway, and that some guys on the Stovebolt forum suggested i just use the sealer. There's one guy down there that's kind of a goofy older guy who seems a little lazy to me, and i'm pretty sure he was the one with the bright idea of bringing it in. I expect NAPA, of all places, to know how to order parts, and not to make it more work for me by not knowing what they're doing. I'm guessing it's the guy(s) in the regional warehouse in Cape Girardeau that are the problem here. I told them a '51 3100. That's pretty easy. Instead i got an empty box and then a 3/4-1 ton gasket, which i'll blame the parts pickers for. Probably have some kids working summer jobs. Anyway, I should get it done today. If it leaks, I'll get a gasket in there.

The gold standard for gaskets back in the dark ages used to be rubberized wool felt. These days, the makers of "Fel-Pro" gaskets can trace their ancestry to "Felt Products Company" from the 1930's, I believe.
Jerry