Considering I’ve already changed my diff like 3 times in the past couple years (I drive a lot of highway so maybe been every 30,000), last time I had already resolved that I wasn’t going to change it anymore because it’s not even a recommended service interval, and I’m convinced due to its location that it’s not meant to be serviced unless it’s being repaired.

Mainly though because that bolt is so ridiculously hard to remove. I’ve had better luck when it’s warmed up, but it’s also close to the hot exhaust so I try to do it when it’s not. But even in 80 degree garage, it just wouldn’t budge.

So if I decide to tackle it again, I really want to replace both of those bolts with a hex and a gasket/washer of sorts. Last time I did it, I used high temp thread sealant which is recommended. So it’s definitely not leaking but definitely not moving either. Any ideas or are we stuck with the original square inserts? Having a washer or gasket there would prevent it from always getting seized every time it’s time to change it…assuming it even needs to be changed regularly to begin with, which I’m convinced it doesn’t.

I'm fairly certain it's pipe thread, so a machine screw wouldn't have the taper needed to seal. I change my differential gear oil every few years. This next service will be with 75w140 Mobil1 and LSD friction modifier. It also give me an opportunity to clean, inspect and/or replace the "breather" so it doesn't build up pressure and start leaking.

I'm having a hell of a time just draining the MT in our 06 Z33. It's a T55, I think, but after repeated heating of the housing and cooling of the plug, the damn thing still won't budge! I guess we're going to vacuum it out with a transfer pump through the fill hole if I have more luck with it. I'm all ears for a different option. I just did a quick check of Fumoto's site and only saw engine oil drain plugs.

HeavyDuty wrote: ↑

Sun Aug 08, 2021 9:28 am

I'm fairly certain it's pipe thread, so a machine screw wouldn't have the taper needed to seal. I change my differential gear oil every few years. This next service will be with 75w140 Mobil1 and LSD friction modifier. It also give me an opportunity to clean, inspect and/or replace the "breather" so it doesn't build up pressure and start leaking.

I'm having a hell of a time just draining the MT in our 06 Z33. It's a T55, I think, but after repeated heating of the housing and cooling of the plug, the damn thing still won't budge! I guess we're going to vacuum it out with a transfer pump through the fill hole if I have more luck with it. I'm all ears for a different option. I just did a quick check of Fumoto's site and only saw engine oil drain plugs.

On previous changes, I would drive around and get everything heated up, then the bolt would come loose. This time I just warmed the engine up to operating temperature but it didn’t get the diff hot enough.

I might just leave it for now. I don’t want to break my only 1/2” ratchet. Though I’ll probably be tempted to try it one more time…especially considering I brought a bottle of 80w90 for a good price and still have a half bottle I want to get rid of. It’s just crazy tight and there’s not a lot of leverage when working from below.

Better yet than ANY kind of pipe thread 'stuff' , especially the Hi-temp , like Red Loctite,,,, is Anti seize .
Ya get the thicker versions of this stuff , a diff. has no real pressure in there ! When you coat the threads heavy-heavy , it seals , gets somewhat solidified - moreso over time . And you can get the F'n thing out again VERY easily by the way . Never use like a Red Loctite or any Hi-temp on stuff like this.
ANTI-SEIZE

macgiver wrote: ↑

Wed Aug 11, 2021 2:07 pm

Better yet than ANY kind of pipe thread 'stuff' , especially the Hi-temp , like Red Loctite,,,, is Anti seize .Ya get the thicker versions of this stuff , a diff. has no real pressure in there ! When you coat the threads heavy-heavy , it seals , gets somewhat solidified - moreso over time . And you can get the F'n thing out again VERY easily by the way . Never use like a Red Loctite or any Hi-temp on stuff like this.
ANTI-SEIZE

+1. It's an NPT plumbing thread and there's also nothing wrong with teflon tape, just don't wrap it to the bottom thread and get teflon in the diff. Big no on Loctite or anything like it. It's a compression thread, that's suicidal.

you know it !! That teflon would be my plan B too VStar .
p.s. you drove a bimmer 650?? I just got hold of a pristine 650i - about the best "driving machine" I've been in.
My humble life??? German engineering - German reliability maybe,, LOL .

macgiver wrote: ↑

Wed Aug 11, 2021 2:34 pm

you know it !! That teflon would be my plan B too VStar . p.s. you drove a bimmer 650?? I just got hold of a pristine 650i - about the best "driving machine" I've been in.
My humble life??? German engineering - German reliability maybe,, LOL .

Nope, 650 Yamaha. Went 106K on the original air-cooled pistons and then got stolen by some twits who probably thought it had 6K. Joke was on them, I'm very sure. I happen to think very kindly of riceburner engineering in general, it's a different philosophy from the euro guys. German bikes have real engineering in them because they need to compete directly with Honda and Yamaha, but the cars? Please. Anybody can build a moon-shot for $500B, that's no feat. Build it for $5B, that deserves kudos. By that standard, the average Honda or Nissan has more engineering in the lug nuts than a Benz has in the whole car. In most of Europe they're taxicabs. I personally know ex-Europeans who still shake their heads at the prices we pay -- without half of it being VAT tax like back home -- then drive off in their US-built riceburners and laugh their a$$es off. We deserve it.

I like and respect your analyses - me , everything is "Disposable" more or less , in the final analysis ?? As it is?
As it should be ? LOL for me !!!

Forgot about this thread! lol.

So I did a round 2 the other day on the fill diff plug while doing my pre-road trip maintenance. The s*** wouldn’t budge! I drove around, albeit not Highway but just a couple of miles and back to warm it up.

This reminds me of the first time I tried to do it. It was like factory sealed and ended up taking it to my mechanic. After that, I was able to remove it 2 more times, but this time I used the thread sealant (which is recommended, and no it’s not thread locker or lock tight or anything…but just a soft sealant with a gum consistency when it cures).

I was literally putting all my strength and might into it, and it just wouldn’t budge. The leverage is an issue, and I was going to use my Jack to push on it, but I couldn’t swivel the ratchet down far enough.

I’m definitely not using that stuff again! I only used it because on previous changes, the diff fluid will seep out thru the threads over time. Plus the package says it prevents seizing and galling of threads and for use in differential plugs and such. In the future I’ll definitely use anti seize instead.

But for now…I think I’ll just take it to a lift again. I’m hoping it doesn’t cost a ridiculous amount, and hoping they don’t recommend to open it up and change the case/gasket even though it does seem to have some seep around the pan. But I just drove 1,200 mile road trip, so the differential fluid is more of a peace of mind and maintenance thing, versus an actual issue. But after a couple of brutal winters and brutal summers, I’m sure it’s time.

As for euro BMWs, I agree! I see a lot of people obsessed with them as a type of status symbol. I just like Infiniti luxury because it always stands out. Like the Q45, FX35 and QX80s are just very strange looking, and people know it’s nice but can’t figure out what it is lol. I still get almost weekly compliments on the Q from strangers, despite the OE paint starting to rapidly decline despite my best efforts to wash and detail once or twice a week due to the vicious Arizona and Florida sun, and now the damn Midwest salt is corroding under body parts that were previously rust free (which my goal is to repaint this year if finances remain steady).