Auto Trac transfer case porosity

[intruder217]

My truck is a 99 Suburban with the AutoTrac 4WD transfer case. I've been chasing a pesky oil leak for some time. The local dealer just looked at it and they've determined that the case has gone porous on one of the seams. they cleaned and sealed it with something called GMS but won't guarantee that it will hold. They want me to let them pull the case and replace it to the tune of 1800 bucks. Well I can buy a truckload of fluid for that amount. Anyone ever heard of this before?

[chevroletmb]

i've never heard or seen magnesium being porous

what part of the t-case is cover with oil?

check you vent tube make sure it's not blocked

unless the case is cracked it should be fixable

[intruder217]

The vent assy was leaking as well and has been replaced. The "porosity" is right near where the rear driveshaft seal presses in. I have yet to get under there myself to see what they did.

[intruder217]

Took a look today as I can still see fluid on the ground. Still bleeding right near the output seal. I can't see any porosity, just seems to be leaking where the seal flange meets the case. The fluid color is red. Did I read somewhere else on this forum that it is supposed to be blue?

[chevroletmb]

autotrac fluid should be blue

the vent for the transmissions is sometime routed right over the t-case

if the fluid in the t-case is blue might want to check the trany vent.

[Nick2000Gmc]

I think the older auto trac fluid was red origanally, unless you have changed it before I think you might have the old auto trac 1 fluid. I think if ya do a search for auto trac fluid you might find the old stuff is red. I would replace that seal and see what happens. I know there is some really good epoxy glues on the market no a days. I've seen stuff that can plug a transformer oil leak ( on the pole ), you just mix it together and slap it on hard and hold it there for a minute and it seals the leak. I have heard guys say hw it has held more than 500 gallons until the morning. I'd call someone like 3M and see what they might have, amazing the stuff they make now a days

[JayMan]

Remember that magnesium is very light, but also brittle. It's VERY easy to fracture/crack if you happen to overtorque fasteners, or even happen to smack it with a ballpeen hammer.

 

Is the leak from the seal itself, or next to the seal??

 

In many cases with a bad seal, the mating surface MUST be absolutely clean and smooth. A slight burr or nick on the seal surface will quickly destroy a seal. Also dirty fluid will grind away a seal.

 

I once had a leaking hub seal on one of my heavy trucks running Eaton Dana HP-40 tandem axles with the Eaton Spicer LMS hub. This is normally a VERY good hub with excellent seals.

 

One seal was leaking from new, even at delivery. Under warranty, they replaced the seal and the drum brake set (Contaminated the shoes with gear oil). Within 5,000km / 3,000mi, leaked again.

 

This went on for 20,000km / 12,000mi and the truck was always in the shop. Finally, babysitted the factory dealer shop and watched as they took the hub apart. Although hard to see, there was a slight burr along the edge of the hub seal surface.

 

Following recommended Spicer service procedures, the burr was removed. That was almost 4 years ago, no leaks since. So it's really important to check minor things like seal surface condition.

 

Have you checked appropriate TSB's for porosity issues? I would think if porosity was a problem, it would have shown up LONG before now.

 

One final thing to try would be to get one of those leak detection dye kits from an autoparts store. Add it to the transfer case (Less than 4 oz and has no effect on lube), then use an appropriate degreaser to get the transfer case spotless.

 

Drive around for a few days and use a "black light" to check exactly where the leak is. Sometimes a leak is sneaky, it will start one place and the fluid will migrate to a different area, sending you off on a goose chase.