243 transfer case questions

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DSinOR

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1996 Yukon 4WD 5.7l with NP243C transfer case.

I removed the driveshaft to change u-joints.
While I was working, about 3/4 quart of ATF dripped out of the transfer case.
I reinstalled the driveshaft.
Then I removed the 30mm top fill plug on the transfer case, to top off the transfer case.
However, as I unscrewed the (top) fill plug by hand, fluid came gushing out like it was over-filled.

I'm trying to figure this out.

I drove 20 miles and then checked the transmission fluid level with engine running. It was right at the top of the hot range.

Does the transfer case share atf with the transmission?

If nearly a quart of atf dripped out of my transfer case while the driveshaft was pulled, then why is the transfer case "overfilled" after I put everything back together?

Any ideas?
Thanks.
 

packer0440

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There should be no “sharing” of oil between the t case and trans. Otherwise it would be a problem with a manual trans. The front bearing retainer of the t case uses RTV to seal it from the trans; only thing I can think of is maybe the truck wasn’t level, I would just keep an eye on the fluid level for any weird things
 

DSinOR

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Thanks for the reply. The truck was level.

I'll keep an eye on it, but for now, it seems like my transfer case was filled way above the fill-plug level.

I'm not even sure how a person could accomplish that. How would you do it?
How could you fill a transfer case so high that fluid comes spewing out of the fill port when you remove the plug?

Also, I've never had any transmission fluid issues. I did all the flushes myself, about 6 of them over the years.
I got the fluid to the correct level and it stayed there for 5 years until the next flush.
 

Schurkey

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Last person to fill the transfer case did it with the ass-end of the truck jacked-up, while the front wheels were still on the ground.

Transfer case tilts forward--fluid level has to come up to reach the fill plug. When the transfer case is level, fluid level is above the fill plug.

This is why it's better to drain the transfer case, then refill based on published capacity, than to "top off" (especially if the person doing the top-off isn't thinking clearly.)
 

RichLo

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Could have also over-filled it if it was sitting on a bench.

Maybe a PO blew up an original t-case because it slowly leaked until dry then way over filled the replacement hoping it wouldn't happen again or something?

Either way, do what Shirkey said, drain it and refill to the proper level with good fresh stuff.
 
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