Oct 14, 2021
2019 ZR1
When you remove the drain and fill plugs for the rear axle there is a round rubber looking flat washer. It turns out that this washer is not available separately from the dealer. It is only available if you purchase the complete drain or fill plug (they are the same part regardless of where they go on the diff and both are magnetic).

On my ZR1 I had already changed out the oil twice and this spring I will do it 1 more time, when I changed it out the 2nd time back in the spring the rubber washer on the drain plug looked really squashed and was in the process of tearing in several spots. This was what led me to visit the dealer to see if it was available separately and when it wasn't I decided to purchase 2 new plugs that I will use on the 3rd change this coming spring.

Not wanting to keep buying plugs just to get that washer if they get wrecked with future oil changes I decided to see what I can find to replace that washer with. After measuring with some calipers there was an oil resistant O-ring that will fit those plugs.

Available on it comes in a package of 20 and are 24mm x20mm x 2mm and fits the plugs perfectly. Oil it with some gear oil before screwing in and tightening. Should be fine for numerous changes and if necessary you have some spares to replace.


An even better solution is to replace the factory flat rubber washer with an alum. crush washer. I've procured 2 of them and when I finish working on test fitting them on the new plugs I bought I'll post up the results here. These will be replaced everytime you do a drain and fill and easily available at a Japanese car dealer so you can stock up on them also should you do lots of drain and fills on your rear axle.

Here are some pics:

AP1&2 shows the Walmart O ring, factory flat rubber washer, the plug itself and the alum crush washer that I have to test fit.
AP3&4 shows the Walmart O ring on the axle plug and AP5-6 shows the plug with the OE flat washer as if you purchased the part from the dealer.

I have not test fitted the alum washer yet as this washer was the closest thing I could find that I can make work on the axle plug. This is an alum washer sold at any Honda dealer part # 90471-PX4-000 (it's their crush washer for the drain plug on most of their auto transmissions and rear diffs). As purchased this washer does not fit onto the Vette plug as the inside diameter is about 1 mm too small so I will need to open up the hole with a dremel so it will fit on. Then I have to check to see if the outside diameter fits inside that stepped lip the GM plug has so there may be a need to dremel the outside diameter down or remove the step on the plug. Yes, a bit of work needed to use the alum crush washer (IMO the better option over using the other 2). When I get to it I'll post the results here.


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FYI You can buy a kit on Amazon with different sizes of aluminum crush rings.
What did u find on Amazon? I only see the crush washer I got with the listed Honda part # sold as a quantity of 20 and the other one is a 14mm washer which is way too small.
Just search “aluminum crush washers kit” on Amazon. You will get a lot of choices.
I did that but what you get is a box full of various alum crush washers and from what description I can gather from the listings none of them have the perfect sizing I need. I also don't need to spend anywhere from $27-45 or more for a box full of 250-300+ alum crush washers of various sizes that for the most part I'll probably have no use for them so no thanks.

I'll stick with my Honda washer that I'll dremel and continue to look for the actual ones that will just "drop" onto the diff plug.
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I'm back on this after leaving it for a while. Just before I brought my car out from winter storage besides the oil change I changed my axle fluid again for the 3rd time. Instead of using the new axle drain plug flat rubber washer from GM I did put those rubber O rings instead and so far so good but I do want to use the alum. crush washers instead.

I dremel those Honda alum. washers and got them to fit perfectly over the fill and drain plugs so when I do the 4th change the metal washers will be going on.

Still trying to find "the" proper metal washer that will work and I have a lead so later today I'm heading out to check and will report back, better to find the proper metal crush washer and not have to dremel the Honda ones.
My lead worked out, I have 2 metal crush washers that slip right onto the drain and fill plugs. I will take pics and post up a more thorough explanation of this particular washer tomorrow.

I measured this washer and checking around on the net guess what???? I found an online place that sells a package of the EXACT flat rubber gasket that fits on the plugs so you could go that route if you want instead of the metal crush washers.

All right here we go.....................more pics re: axle plug washers (APW)

APW 1 shows the honda washers mentioned back when I first did this thread, first washer is the regular Honda washer part # 90471-PX4-000, 2nd washer was the washer I dremeled first to open the inside diameter. I did a shitty job of the first one and it does go onto the axle plug but you have to lightly work the washer past the threads. 3rd washer was dremeled a lot better than the 2nd and that washer slips right on no problem shown in APW 2&3.....................notice it fits also properly inside the step surrounding the outside edge of the plug. I have spare Honda washers so I'm tossing the first one I did and will do another one so it looks like the washer that slips right on.

APW 4 are the 2 metal washers I got from my lead............................Oh the Humanity!!!! at a Chrysler/Dodge dealer. It carries part # MFSI 2167 and it fits a drain plug on some kind Cummins diesel engine that the Ram trucks might have (parts guy didn't get specific about exactly what it fits maybe having the ZR1 T shirt on yesterday made him not want to disclose too much about exactly what this washer fits). Notice that this washer is not a metal flat washer but kind of a spring washer (flat on 1 side, slightly curved surface on the other). Parts guy mentioned that it can be reused several times before needing replacement so if you change your axle fluid a lot (like me, especially when I start tracking my car) you can get two and know you can get several uses out of it. Not cheap though each washer was $5.75 on the invoice (or he jammed me because of the ZR1 shirt LOL).....................whatever I'm driving a $2XX,XXX ride so spending a bit for something I want isn't an issue.

APW 5,6,7 shows the Dodge washer in the plug, fits like a glove so again next axle fluid change I'll decide on either using these or the dremeled Honda washers. Notice the APW 7 pic the Dodge washer is metal and not alum like the Honda washers. I had a slight concern about that after purchase but I was going up to see my friend who is a Shop Foreman at the Honda dealer I worked at a long time ago (I call him Mr. GM Freak, loves Camaros and Corvettes and had a 1976 Trans Am back in the day). My concern was corrosion if the metal washer started rusting against the alum casing of the diff. He told me not to be worried about it as there won't really be any corrosion at all on the washer. The plug itself is also metal so that put my concern at ease.

If I ever make it back to the US on a road trip or something and staying overnight somewhere I'll most likely will get a package of those proper GM flat rubber washer posted above this post shipped to my hotel for me to pick up so that way I have choice as to what I want to use when I do my axle fluid swaps and I won't have to keep buying axle drain/fill plugs just to get that washer.



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Here is a little update to what's been going on here with regards to my car and changing diff fluid. As mentioned in another post back in Oct. 2022 I did another fluid change shortly before parking the car for the winter. On this change I decided to try the "Mopar" spring washers shown in this post above with all the pics.

Once I parked the car for winter storage I would check that area the odd time and noticed a sweat at the bottom of both plugs. I'd wipe it and leave it for a few days and it would continue to have a sweat.

Back in mid Feb. I decided to pull the plugs and changed them out for the "Honda" metal washers that I dremelled for them to fit over the plugs. Put them back and still developed a sweat that became a hanging drip at the fill plug when I checked it last week after coming home from holidays.

Basically it looks like all this effort to find a washer that won't disintegrate like the OE rubber washer was all for not. This morning I pulled both plugs, drained my fresh fluid into a container, refill and put the plugs back in with the OE washer. At the moment there is no issue but I'll give it a few hours then go out and check to make sure no signs of fluid leakage is there.

1 note, those plugs DO NOT need to be tightened a lot..............go hand tight then just a snug with a ratchet (I use a 1/4" drive ratchet with a 1/4 to 3/8" square adapter). If you decide to really reef on it to tighten is when you will damage those rubber washers. If no leaks after my check I will get a marker and mark where the plug is in relation to a mark on the case so in the future I only tighten to that point.

Edit: 2 checks several hours apart....... all good no more drip/sweat at the plugs and position marked. 1 more check in the morning tomorrow should be good to go! 👍

Edit #2: checked it this more sweat or hanging drip at the plugs.................OE washer for the win ALA it doesn't get wrecked.
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Just another little update now just over a month since the above post.......................all good and no residue at the plugs at all (totally dry). I am now satisfied that proper tightening when using the OE washers will do the trick.
That's quite a play by play Afterimage.... I just finished doing an oil change as well as the diff fluid. Have been using the same washesr and plugs on both oil drain plugs (dry sump engine) as well as the diff plug and washer. Never had a leak yet.... but, its prob best that I purchase a new set.
Very well explained and supported with great photos... Thanks for sharing!
That's quite a play by play Afterimage.... I just finished doing an oil change as well as the diff fluid. Have been using the same washesr and plugs on both oil drain plugs (dry sump engine) as well as the diff plug and washer. Never had a leak yet.... but, its prob best that I purchase a new set.
I never had any issues with the engine oil drain plugs and the washers that came on them. I have stocked up on a bunch of the rubber seals for the drain plugs (engine) and will change them out every few years. I also religiously torque the plugs to spec (18 ft./lbs) and those plugs are marked also with a paint pen.

The diff plug seals were slightly crunched the first time I removed them to change out the diff fluid (when car was new 4 years ago @ 1000kms) so why I bought new plugs with the new seals included so in the future they won't get wrecked. I would've preferred the metal crush washer option which is why I went through this whole fiasco only to just go back to the OE diff plug rubber washers.
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