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Sight Glass for Trans and T case


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Hey guys,

I was thinking today and I decided it would be very convenient to have a sight glass in my nv4500 fill plug and my nv241dhd fill plug. Maybe eventually the front and rear diffs as well. Now I know from Mike's thread that the trans fill plug is 3/4 npt. What I don't know is, the t case fill plug size, and diff fill plug size. I'm also wondering if anyone has input on anything special to look for or avoid with a sight glass for this specific application? Also, anyone have a good source for these?

thanks!

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Yes something like that would be just the thing. I'm just not sure of the best place to get one. I was looking at this site so far https://m.mscdirect.com/mobileweb/category?catId=12107797&searchTerm= or this

https://m.grainger.com/mobile/product/LUBE-Gage-1U917

I just wasn't sure if there is anything in particular I should look for.

Edited by leathermaneod
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Lol we must have been posting at the exact same time with the same link. I'll certainly keep the thread updated for you. I do hope someone else chimes in that knows the size on the t case though. Maybe it's the same as the trans. I guess the diffs might even be the same too. Only thing I'm a little concerned about would be getting a brass one. I'm not sure if it would stand up to how tight those plugs sometimes need to be...

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Thank you! I'll have to do some more digging on that. I've also still got to find a good source for sight glass plugs. Anyone have any input on what material the plug should be? Does it need to match the case material i.e. steel for the trans and diffs and aluminum for the t case?

Edited by leathermaneod
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I can see putting a sight glass plug in for the axles or transmission. As for the transfer case it might be hard to get extra fluid in to see it in the sight glass. Little knowledge on sight glasses. Like old Honda motorcycles had them back in the day instead of a dip stick. Now the Honda motorcycle where horrid because about every year or two you had to pull the clutch cover and using a q-tip clean the glass so you could see the oil level. Yamaha got smart and used a wiper that you spun using a screwdriver to clean the glass. So consider the fact that crud will cloud the sight lass over time. Just like pulling the differential cover and everything has coating of the black that just wipes off.

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Thanks for the tip and the info! I wonder if a sight glass with a reflector would be better or worse for keeping it clean? I'm having a hard time finding these locally so I'm probably going to have to order off the net. I wanna try my best to get it right the first time.

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15 hours ago, leathermaneod said:

Thank you! I'll have to do some more digging on that. I've also still got to find a good source for sight glass plugs. Anyone have any input on what material the plug should be? Does it need to match the case material i.e. steel for the trans and diffs and aluminum for the t case?

On the industrial side of things all the sight glasses I've seen are brass screwed into in a steel or aluminum case. 

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The transmission and differentials are regular 3/4" NPT.  But the transfer case is tapered 22x1.5mm.  Not very typical.

 

I installed a sight plug on the transmission as I have it overfilled and use the sight glass as a visual confirmation for the amount of fluid in the transmission as much as its color condition.....because obviously (and as already pointed out by others) the level of the fluid would have to be overfilled otherwise you wouldn't see anything unless you were driving and fluid was sloshing.

 

Important though is that you'll want to make sure the temperature rating of the sight glass you're looking at.  They're not all high temp and some are actually so low of temperature rating that I wouldn't suggest using it because you wouldn't want to chance the sight glass failing.

 

I eventually found a 500*F sight glass in 3/4" NPT, although it didn't come with a reflector, but I wasn't able to find the right thread pitch in a sight glass for the transfer case which also had the correct temperature range.

 

I'll post some pictures as to what I installed on the transmission and the solution to not finding what I wanted for the transfer case tomorrow. :thumbup2:

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