Has anyone played around with the idea of installing a sightglass in place of the plug that's generally used to drain oil from the TC...
I realize that it can't be used as an oil level indicator, more as a reassurance that oil is still there

I found this glass used in a whipple SC

 

I know this is going to sound odd, but that is too big to fit in where it would need to go. A straight plug with the center square drive has its outer threads rubbing on the edge of the case (you can see where the threads start about a 1/2" up the side of the transfer case. So, while that is a good idea, it wouldn't work on our cars unless there is another design out there. You could possibly get away with something designed for say a 3/8" NPT opening and then using a 3/8-1/2" NPT adapter, make it work that way. But, you are still having to modify the adapter to cut it down slightly and then you are still running a chance of it not working.

 

I've found a few sites that carry different sizes, the Whipple one was for effect as it were...
one site has a bulb type that sticks out about an inch, but is only rates to 200°f... i'd imagine that is too close to the operating temps down there...

EPCO Products, Inc. Zero-Leak Gold Plugs Page

 

another site

Safety valve & liquid level gauge manufacturer - Seetru

 

sizing chart

 

Kota62, like I get into in my first post, any sight glass that uses the 1/2" NPT threads is going to be a hard fit. Looking at the chart from your last post, you can possibly make the 1/4" NPT fitting work without having to modify the sight glass body. But, you are still going to need the sight glass to be extended out about 1" to make it all work (can't go flush as you would still have around 0.050" of interference). If you do go this way, I would highly recommend using red loctite to seal the sight glass to your adapter. This will be needed as you will end up removing the hex top of the adapter to allow the adapter to screw in. So, the next time you go to do a TC fluid change, if you don't loctite the components together, how would you remove the adapter? Atleast with the loctite, you can apply a wrench to the sightglass and use that to undo the adapter.

Something else to consider: if you install the sightglass, how are you getting the fluid back into the TC? Something to ponder. Sure, you can angle the car to get the fluid in, but that is going to be about your only option. I don't see the "quick swap" method working too well for something like this.

I'm not trying to steer you away from this as I think it is a very worthwhile thing to look into, unfortunately, due to design, it may not be practical. It is easier to work it out thinking about it than to spend the money on the parts and then start having to cut, modify, adapt, etc to get something that may or may not work. I'm willing to help out and attempt to make this work for I have already been down this road in making a valve that adapts in to allow TC fluid changes.

 

Thermo;
i do appreciate your feedback on this
I would do the jack up & fill procedure for oil changes understanding that i would lose the quick fill/drain usefulness of those cool drains
looking at pics of the TC i felt there was enough room to install a sightglass w/o mod. I was unaware of the tight depth tolerance, so that needs to be addressed
The problem for me is that i'm on the road 3 weeks/month, so, since i bought my Jag in May i've put a whopping 90 miles on her...

P.S. what size is the plug currently installed

Thanks again
Gary

 

Found a 1/2" NPT high pressure sight glass online for 10 bux...
If i ever stay home long enough this could be quite an interesting science project

 

Kota, the drain hole in the transfer case is a 1/2" NPT fitting. I seem to recall the one on my transfer case being really close. THe picture that you show would lead you to believe that you have room to play with. For $10, I would say to give it a try. Not that big of an investment overall. I know when I was making my adapter, I had to grind the hex part of the adapter off due to clearance issues.

Give it a whirl and see what happens. It is a good idea to swap out the fluid anyways, so, one more reason to get under the car and check this out.

 

Well that's a picture I took of my transfer case, and the angle is deceiving. The edge that dips down in front of the drain hole comes down far enough that it blocks head-on access to the hole.

You will have 3/4" or maybe one inch of clearance, with slightly more and less than that as you try to rotate any fitting.

 

Gold:
your pic is much appreciated, in the 3 months i've owed my Jag, i've read, copied text & pics till my hard drive is ready to burst... lol
now if i could drive it more often