Flat, gear-driven t-case oiling

XJsavage

XJsavage

CounterCulture
Joined
Aug 15, 2009
Location
Lyle's Ford SC
I have an NP205 transfer case behind my 4l80e automatic that I've clocked completely flat. Specs say that they take 2-2.5 quarts of gear oil to properly lubricate it. When you look at the fill line on a stock clocked transfer case it about halfway covers the front output gear and bearings within.
Example:
ai552.photobucket.com_albums_jj335_jrhxj1_205fillline_zps02d49b6c.jpg

And here is where I'm at with exactly two quarts of Amsoil 75-120 synthetic, only about an inch covering the bottom of the front output gearset.
ai552.photobucket.com_albums_jj335_jrhxj1_IMG_20140627_092540_060_zpswr4ze5yp.jpg

So should I keep adding more until the oil line covers the halfway point of the gear? Or is that too much? I have two more quarts I can add if need be.
This vehicle will get driven at highway speeds in 2hi for several hundred of miles at a time up to 85 mph, (I mean 70~speed limit), and drag raced every blue moon. Will also be driven in 4-hi/lo for extended periods of time as well.
 
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transman731 said:
i would add a little more, you just don't want it higher than the output seals. the good thing is that the t-case is lubed by slinging oil so it isn't as big of a deal as we would think.
Click to expand...
Makes sense. I was gonna put another quart in just to see where it sits. I think the happy medium will be just below the center of the outputs. Certainly don't need oil seeping past the output seals and the LAST thing I need is for it to seep past the input seal and mixing with the transmission fluid. I know the input seal is good though. Thanks!
 
If I were you....

Eventually, I might would pull the cover off the back and drill/tap another hole for a fill plug. Just a thought. It may not be a huge deal, but it might make filling it easier. Where do you fill it now? The top hole for the sight tube?
 
ai552.photobucket.com_albums_jj335_jrhxj1_IMG_20140627_084300_013_zpsuxmeqn3x.jpg
Filling is the easy part.... Gravity and hydrostatic pressure*
Inside of the case will be the same level as in the sight tube.
 
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Interesting way to fill a t-case. I guess as often as a case needs refilling, it is no big deal. If it were more frequent intervals, I'd side with @Croatan_Kid 's idea.
 
Well.. Given the lack of room under there if I did have a plug drilled and tapped on the top half of the case there's no way I could get a funnel in the hole. I'd have to cut a hole in my floor pans to get any fall to it lol. This way is by far the best. Clean and exact. I can precisely monitor the level ad I'm filling it and forever after. No guesswork whatsoever.
 
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Well I use this to fill mine, which you could use regardless of how close to the floorboard the hole is.


ImageUploadedByTapatalk1403993025.001304.jpg
 
I've done that before on my Dana 300s, 231's, 242's, etc. Got tired of carrying the tube around which is going to be full of oil inside and drips all on inside of my tool bag. To each his own. This way uses hydrostatic pressure and requires no tools other than funnel and is a lot cleaner. I just couldn't see tapping yet another hole in the not-so-thick aluminum cover just to add oil. Thanks though
 
I thought about that as well. Just wasn't sure how well the weight/pressure of the fluid in the funnel pushed the rest of it inside the case. I totally agree that the cover there isn't all that beefy. I just figured it would be easier to fill from an unobstructed hole.
 
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