Oil leak/drip from rear of T-case?

[Martinjmpr]

So the wife got after me the other day for my truck leaving oil stains in the driveway. I checked and dang if she isn't right! So I got on the creeper and looked underneath. At first I thought maybe when my transmission was rebuilt in August they didn't tighten something up, but the leak didn't appear to be ATF, and when I got on the creeper it looked like the leak was actually coming from the back of the transfer case, where the U-joint attaches.
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Sorry for the crappy cell pics, best I can do.
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The leak isn't a LOT, maybe a couple of drips after the truck has been sitting a half hour or so but it's more than the truck has ever done before so it's got me concerned. Anyone else had a similar problem? Is there a relatively easy or inexpensive fix? I'd hate to think that the T-case needs to be pulled to fix this but we're moving into a new house next week and I really don't want to leak on the driveway!
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Thanks in advance. BTW vehicle is a 2004 Chevy Suburban LT 1500, 5.3, 4x4, with about 154,000 miles on it.

 

[rayra]

Your picture appears to be of the transmission tailshaft seal on the rear driveshaft, not the transfer case front seal. Isn't that the fuel tank evap cannister (black rectangle box with the crap sticking out of the top / front) in the background? 't-case' usually refers to transfer case, not transmission case.

Most seals like that are made to be externally replaceable. You just drop the attached driveshaft end, pull out the output shaft, pry out the seal and its soft metal housing, clean the seal area and tap in the replacement seal. Reassemble. Not even an hour's work.
Be prepared for fluid/oil to run out when you pull the shaft. Be prepared to replace it after reassembly. BEFORE disassembly, make some chalk reference marks on the tailshaft / trans housing. Chock your wheels. Use jackstands.

A $20 Haynes manual describes the basic procedures. Along with a wealth of other 'home mechanic' -accessible repairs.

This is the part for the K1500 for the 4L60E trans. It's all of $5. Shouldn't be more than twice that at any local parts store.
http://www.rockauto.com/en/moreinfo.php?pk=1839182&cc=1380327&jsn=590



eta - the green part is the metal flange that press-fits into the transmission tailshaft housing opening. That's what you'll tap on drive it in. The bigger wider flatter tool you can use, the better. I don't think a normal seal seating tool will work, those are usualyl a flat disc and you need a cup shape that fits over the protruding rubber boot on this design.

The key is just lightly tap and work opposing sides somewhat like tightening lug nuts. The idea is to seat the seat levelly all around as you go. Drive it too hard, get it cockeyed, it will gouge up the coating on that metal flange to a degree that your new seal might leak. Just lightly tap it all around with a smooth-faced hammer and you'll be fine. Or use a small chunk of 2x4 as a driver. Place it across as much of the seal face as you can, before tapping the wood with the hammer.

 

[jeep-N-montero]

My educated guess it that at some point the rusted section of the yoke entered the lip of the new seal and damaged it. But as mentioned it is a very easy task to replace it, if under warranty from the rebuild they may replace it for free or cheap if you are not up to the task yourself.

 

[Martinjmpr]

My educated guess it that at some point the rusted section of the yoke entered the lip of the new seal and damaged it. But as mentioned it is a very easy task to replace it, if under warranty from the rebuild they may replace it for free or cheap if you are not up to the task yourself.

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Well, in addition to this being a little outside my comfort zone, we are ********** in the middle of moving which means most of my tools are in boxes, so I'll give the transmission repair shop a call.
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Thanks for the input, I figured it was probably something simple but you know, any time oil is leaking it's a cause for concern (unless it's a Triumph motorcycle in which case oil leaking is good because it means that it still has oil in it! )

 

[rayra]

1/2" open wrench (or whatever it is these days, 12mm? 13mm?) for the nut/bolts on the rear axle u-joint trunnion bolts trapping the rear U-joint.
A large screwdriver or small pry bar to pop the U-joint loose.
A seal puller or the same large screw driver or pry bar (it will be a lot easier with a proper seal pulling tool, a few bucks at any auto parts store)
A 12oz hammer.
A catch pan.

And maybe a bit of emery / crocus / 400grit to work the exposed section of the forward yoke. Jeep-n-Montero is likely correct in his supposition. Especially if you are driving it around fully loaded / squatting and bottoming things out often. That's what happens when the suspension compresses, that front yoke goes deeper into the tailshaft housing.
SAND SPARINGLY. Just enough to take the high points off any rust. DON'T try to remove all traces of rust or you will likely reduce the diameter enough to make it leak that way instead.


But it it's just a few drops you've got all the time you want to take. Just check your trans fluid level more often. It will take a LONG time before such a drip makes any mechanical difference. The only urgency is the driveway spotting.

Martin I encourage you to stretch that 'comfort zone'. It's an easy fix and good experience.


one last bit, there is a plastic tool, a cylindrical plug that you can jam in the trans tailshaft when you pull the driveshaft, to limit the spill of trans fluid, but it's moot since you are after the seal itself. It IS going to pour out. You can limit that somewhat if you can park it nose down on a suitable slope.


eta replacement slip yokes are $90-275. GM part #12471638. The GM part is on the top end of price, the aftermarket vendors on the lower end. And changing the yoke means disassembling the front U-joint. And at that point, driveshaft off and all, you might as well change your u-joints too AND your rear pinion yoke seal too. But I'm not even sure the pinion yoke comes out without opening the rear end. I don't think it does.


eta the tools are simple and inexpensive.

 

['round n' back again]

spicer parts for the slip yoke. ebay-good. crocus cloth, cheaper,- better. find out why the slip yoke sunk so far into tailshaft -best. there is a spec that details how far that yoke should be inserted with rig at rest.

replace u joints only, if sloppy out of spec as per mfgr. every time you break that connection you risk/invite vibrations


rear pinion yoke seal can be tricky if there is a crush sleeve involved.