ON my new diesel rig, the output shaft leaks gear oil. It only does it when I am driving, and I've replaced the seal. The seal rides good on the driveshaft slip yoke, but I'm still getting a drip while driving. It's bad enough to speckle the back of the truck, and underneath is damp from gear oil. You can see gear oil appearing to leak onto the shiny slip yoke surface, but I can't tell how it is getting past that seal.

Any ideas?

1st,,,use a Mitsu brand seal,,,,check the special parts repos on this site.
OEM seal has more sealing surfaces than an aftermaket.
It's not a very hard to do repair.
The transfer case Slip yoke seals tend to leak a bit, esp. from vibrations in driveshaft and possible slop from wear in output cover bushing and slop on output splines.

sounds like a bad bushing /oil leaking past the yoke splines/weep hole in the end of the yoke / o-ring gone

It seems to be dripping down off of the yoke. I don't think it's leaking at the splines/plug. I defiantly looked there. I'll check on getting an OEM seal for this.

Maybe there is a vent for this thing that is plugged??

It's leaking more than normal for sure. I'm ok with wet seals, and a drip every now and then, but this is leaking enough for me to consider it a problem.

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Got a wear groove on the yoke shaft? Tranny vent is a rubber mushroom on the top, on the shifter plate, I think.

The bushing has a spiral groove which is supposed to carry seepage back to the tcase direction in forward travel. I'd check it for a dam.

The yoke do have a tendency to leak out the plug hole. I'd look at some rtv to reseal it.

The yoke feels smooth, and the seal rides on it really nice. I slipped it up on the yoke before I installed it, and it seemd like it was perfect.

What do you mean dam? I looked up in there as far as I could see, and saw nothing out of the ordinary.

Mine leaked until i replaced it with stock seal. but the old seal was very worn.

the spiral groove is about 3/16' wide, with a rounded bottom like it was machined with a ball mill. If it has crud in it, the crud will block the flow back up the spiral into the tcase, and the pressure may force lube past the seal. You can pull the dust protector to get a better look - hard to see past the splined output shaft. Is the yoke still non-rocking on the splines? Still tight? Did the spring come out of the seal as it was driven? I always pack the spring groove with axle grease before I drive it to keep the spring in, and lube the sealing surface with either silicone lube or axle grease.

OK got that grocked....


Already done. PO pulled it off, and it was in the parts box that came with the truck. I'm guessing he had troubles with it also.



No.. Not tight. I could move it laterally around a bit. It was pretty clunky..... Should I start shopping for a new yoke?



Spring def did not come out. I put a lil bit of ultrablack RTV on the sealing surface between the seal, and housing. Lip of the seal was lubed with gear oil before the driveshaft went back in. This is such a simple thing, I just don't know why it wont cooperate.

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If the yoke is rocky, the seal won't seal up, or last long. Either the yoke is worn on the splined surface, or the tcase output shaft housing bushing is worn, maybe both. The yoke material is softer than the bushing, so hopefully the yoke is worn on the splines.