Differential Drain Plug Dilemma

[G35fromTO]

So I've been trying to change the differential fluid. First thing I did was read on here what sort of a key I would need for the drain and fill plug. I found out that it's a 10mm hex and got that socket. Well, when I tried to unscrew either of the plugs (started off with the fill), the 10mm doesn't fit. Basically, it's too large and it's the same on each of the plugs.

The key that almost fits perfectly is a 3/8" hex, however, it doesn't sit flush and is a little bit loose so I feel like if I start trying to use it and apply force, I might actually round out the drain plug head.

It seems bizarre, but can it be that my differential drain and fill plugs aren't 10mm? I know the tranny's plugs are 10mm and the 10mm hex key that I had fit in those perfectly.

LOL I've even gone as far as to buy different hex sets and try the 10mm key from each one in case the first one I had was somehow not fabricated accurately

If anyone could shed some light on this “mystery” that would be awesome and greatly appreciated!

[EncoreCestMoi]

Originally Posted by G35fromTO

So I've been trying to change the differential fluid. First thing I did was read on here what sort of a key I would need for the drain and fill plug. I found out that it's a 10mm hex and got that socket. Well, when I tried to unscrew either of the plugs (started off with the fill), the 10mm doesn't fit. Basically, it's too large and it's the same on each of the plugs.

The key that almost fits perfectly is a 3/8" hex, however, it doesn't sit flush and is a little bit loose so I feel like if I start trying to use it and apply force, I might actually round out the drain plug head.

It seems bizarre, but can it be that my differential drain and fill plugs aren't 10mm? I know the tranny's plugs are 10mm and the 10mm hex key that I had fit in those perfectly.

LOL I've even gone as far as to buy different hex sets and try the 10mm key from each one in case the first one I had was somehow not fabricated accurately

If anyone could shed some light on this “mystery” that would be awesome and greatly appreciated!

somethings jacked up. I did both my trans and differential about a month ago and the drain plugs, fill plugs and washers are exactly the same all around.

[SiouxFallsG35]

I'd verify that you don't have crud built up in the female hex portion of the plug. Maybe work it over with a small screw driver to get the caked on stuff out.

1st owner, 2nd owner - any chance it's been worked on in the past?

[G35fromTO]

I've thought about the possibility of it being some built-up but BOTH of the plugs and so much!? Ok, if it's not raining tomorrow after work, I'm going under the car and giving it a try. Would spraying some W40 and then using a small screw driver head to scrape off any possible built-up work?

I'm the 2nd owner. The differential fluid was changed at the stealership by the previous owner. Neither of the plugs show damage but who knows...

[bbs350z]

Originally Posted by G35fromTO

I've thought about the possibility of it being some built-up but BOTH of the plugs and so much!? Ok, if it's not raining tomorrow after work, I'm going under the car and giving it a try. Would spraying some W40 and then using a small screw driver head to scrape off any possible built-up work?

I'm the 2nd owner. The differential fluid was changed at the stealership by the previous owner. Neither of the plugs show damage but who knows...

believe it or not they do see alot of junk,eialy if you drive it year round. my z's diff had alot of buildup in the diff, and that was at 44k being a weekend car

[itgogitrev]

My rear diff was the same way, lotta salt this past winter and my driveway was dirt and gravel until July. I let the bolts soak in the PB blaster and then cleaned them with a brass bristle brush. Took 4 hours, but the hex head finally fit.

[EncoreCestMoi]

as much as california taxes bug it's times like these I appreciate it. I crawl under the car and other than some water spots here and there it is factory fresh. nothing rusts, nothing seizes and things unscrew as easy as the day they were tightened

[twin001]

should be a 10mm, clean it out and try again.

[ttrank]

I just changed my tranny fluid and built a diff cooler. All the fill and drain plugs are the same size (10mm).

[ttrank]

Sounds like yours may have some rust or gunk in there that needs cleaned out.

[Tollboothwilley]

You built a diff cooler Tim? You got pics of that? Post those up somewhere.

[G35fromTO]

Well I tried PB Blaster and scraping anything out of there. Nothing. I'm pretty much certain now that the dealership messed them up (originally that's what I was thinking) when the previous owner replaced the fluid. Each side of the hex plug almost has like a grove on it.

The fill plug will allow the hex socket to go in slightly more than the drain plug. What I ended up trying is lightly hammering the socket into the plugs and that seems to work. They go in and stay but very very tightly. That's definitely not normal. I didn't go too far with that because I want to get two replacement plugs so I only have to take these off and never use them again.

Don't know how they did it... but I wouldn't dismiss them using a 3/8" hex key and a power tool.

I almost feel like going back to the dealership and demanding 2 plugs from them but I know that won’t happen. Anyways, hopefully they aren’t too expensive and I’m going to try and pick them up from a Nissan dealer.

[Tollboothwilley]

Glad you got them off.