Transfer case drain plug leaking

sierra5454 · January 25, 2020

It looks like I am dripping transmission fluid from the transfers case at the drain plug. I ordered a new plug and will drain and refill with new Dextron VI. When I install the new drain plug, should I coat the outer threads with black permatex? Will this make it very difficult to remove the plug should I need to in the future?

Thanks,

davester · January 25, 2020

First, are you absolutely sure the drain plug is leaking, not that fluid is coming from further up.

Second, with the drain plug out, after all the fluid is out, really clean the area and check if the housing is cracked, say, from someone overtightening the drain plug.

Third, check the case to see if it has a hole where the "gm pump rub" problem rubs a hole in the case.

Fourth, I would suggest not putting permatex on it. Just get a torque wrench and use it to torque it down to 15 ft/lbs (that's from my '04 sierra full-service manual).

Fifth, the proper fluid for it is DexIII. Find some that says it is DexII. DexVI was known to cause leaks when put in older vehicles (particularly, made prior to when DexVI became a specification), as the seals weren't designed for it. Even in '06, the transmission was specced to get DexVI, but the transfer case still was supposed to be filled with DexIII.

sierra5454 · January 25, 2020

Owner's manual does call for Dex VI. I'll have do take another look, but there wasn't any obvious fluid leaking down from above the plug. This is on a 2012 sierra.

davester · January 25, 2020

Oh, I was looking at the truck at the bottom of your post... Forget the thing about pump rub and DexIII, and the torque for the drain plug may be different for your transfer case.

CapitalTruck · January 26, 2020

You gotta use thread sealer on that plug. Its white stuff in small white tube made by permatex. It isnt any kind of loctite.

sierra5454 · January 26, 2020

Would it require the high temp or high performance?

www.permatex.com/product-category/thread-compounds/thread-sealants/

CapitalTruck · January 26, 2020

I used the one in the red package (high temp). This is what I had on hand and seems to work fine.

CapitalTruck · January 26, 2020

Just be sure to work the stuff around in the tube before you use it. You know how mustard always dumps water on your hotdog before mustard comes out? This stuff kind of does the same. So, I always squirt a little on a towel before I use it.

sierra5454 · January 26, 2020

Much appreciated.

sierra5454 · January 26, 2020

Looks like the housing is cracked. I was able to see the crack after putting the new drain plug in. I drained the fluid, cleaned it with brake parts cleaner and sanded the area around the crack. I put on some JB weld and holding out hope that this will seal it.

It looks like a new housing is about $250 on rockauto.com. ACDELCO 19302452 GM Original Equipment . Any idea what I'm looking at to get this fixed?

davester · January 26, 2020

Sorry, no idea. I know for the previous generation truck (GMT800's), it's

-remove the transfer case (the case to transmission bolts SUCK, particularly the one at the very top)

-remove the VSS sensor

-unclip a retaining clip for the rear bearing

-remove all the bolts around the edge,

-then the housing splits (takes some careful prying to get rear half off the alignment pins)

-clean off all the old sealant between the case halves

-put free sealant (anaerobic flange sealant) around the inside edge of one half (enough, but not too much, as the excess that squeezes out on the inside winds up trying to plug the inlet screen to the oil pump)

-put the case halves together, on the alignment pins and torque them down (I do it in 2 passes, first time snug, then second time torqued down to the right value, in a criss-cross pattern)

-put the retaining clip on the rear bearing

-reinstall the VSS sensor

-install tc into vehicle and fill

Removal/installation, you really want a second person to help, even with something like a transmission jack to lift it, as it doesn't have a nice flat lifting surface and it has to be rotated in 2 directions to get past the crossmember just behind the TC.

Yours is different, in that it has those two visible machined sections where something bolts onto, and perhaps there's more stuff to bolt on to the inside. As well, there are likely bushings, seals and bearings you will have to install in that cover before it can be installed, that you will also have to buy, as typically you will fatally damage them trying to get them out of the old case half.

You might find youtube video's on how to do this job, and maybe study online parts diagrams for the transfer case, as you've identified the specific transfer case you have (hopefully!). Most like, info about your TC is less commonly available than it is for mine, as the GMT800 TC's had the pump-rub problem, so it was pretty commonplace to remove them, do a pump rub fix that involved splitting the TC, and then reinstall them. Later trucks didn't have that problem, so people only dealt with the TC when they failed.

Finally, going forward, find out what torque value to use for the drain and fill plugs, so the new case doesn't crack again...