Leak at transmission output, transfer case input. Advice please!

So, in addition to many other problems I've been having with my truck (all of which started shortly after having a new clutch installed), it now appears I have a very slow leak where the transmission meets the transfer case.

my truck: 1998 V6 3.4L 4X4 5-speed

I have searched around these forums and I get that the leak is probably the output seal of the trans, or the input seal of the transfer case, or both. The leak is really slow: I get about a fraction of a teaspoon every 100 miles or so. It doesn't even drip to the ground, it just sort of collects at the bottom of the T-case.

My questions:

1) What causes those seals to fail? Could it be related to having a new clutch installed? I don't really see how. Another thought: Is it possible that never using 4WD could cause the seals to dry out or fail? The manual says you should drive in 4WD at least 10 miles per month to keep everything lubricated. I bought the truck with 100k miles on it, and the original owner NEVER used 4WD. I have used it regularly since I bought it, so maybe I am shaking things up or stressing things out??

2) Could over-filling the transmission or transfer case cause this kind of problem? Last year the original owner drained and filled both diffs, the trans and the t-case. I opened the fill plugs on all of them and they were all WAY over filled. As a side note: are there any problems at all that could be caused by over-filling the diffs/trans/t-case?

3) How long can I let this problem go? Its such a slow leak, I kinda just feel like ignoring it and keeping an eye on oil levels for the time being. obviously if i let the oil drain completely, that would be terrible. but if I keep it topped off, any long term consequences?

4) last question: the mechanic at the toyota dealer told me they would have to drop the transmission to replace the seals. That sounds wrong to me. cant they just remove the t-case and work underneath the truck? What do y'all say?

 

He's not wrong, your trans is sealed in back where transfer bolts up & in front where it slides into the pressure plate/disk/into the end of the crank

 

The mechanic did the seal at the front of the Trans when he did the clutch, so all that needs to be fixed are the seals where the Trans and t-case meet. Still need to drop the Trans??

 

If the fronts been done then no the trans doesn't need to come down just the transfer but it should've at least been brought to your attention something like "Hey since we're pulling the trans anyway let's re seal everything .?" (within reason of course)

 

Yea, I hear ya. They did recommend the rear main seal, which I had them do, but that's all. I wish I had thought of the others! NOW I KNOW!

Well, if they don't have to drop the Trans to take care of this seal, at least it won't be TOO expensive. Maybe I'll even do it myself..

Thanks for the advice!