I have a leak from rear of my transfer case, I believe it is a NP205.

Truck: 77 F-150 Custom, 351 W, 4-speed Manual.

What type of gear oil should I use for this transfer case? And, where is the leak coming is it a seal or from the plug/vent on top?


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Thanks!

 

from the pics it looks like its leaking from the vent. check your fluid level to make sure it isnt over full.

 

Mine looks exactly like yours and I think it leaks out the vent too. It's at the correct level so I don't have a clue why it comes out the vent. It is filled with 90w but a multigrade would be better for winter weather.

 

Bump. Same issue, leaking from the vent tube.

The NP205 fluid level hasn't been touched in almost two years when it was changed by the previous owner. I have a heated garage and it is damn cold this week.

Drove the truck to work yesterday, just over a mile and home after work, no issues, parked in garage.

Today before going to work I notice a 6" diameter puddle of clean gear oil on the garage floor under the truck, looks like it came from the vent on the NP205. I drove it to work and looked where I parked yesterday, pavement is dry. Drive home for lunch, put it in the garage and rode back to work with my wife (we work at the same place).

Come home tonight after work, truck been siting in the heated garage for the afternoon and there is another puddle on the floor. Stuck my phone up there and it is obviously leaking from the vent.

Suggestions?

 

Those are some weird symptoms... Maybe the case is pressurized somehow from the cold to warm cycle? but.. then how would the oil get there... hmm.. *shrugs* ah goot nuttin'!

But, what about sticking a hose on it? or replace that vent with a nipple (snickers) and run that way up high, like the axle vent is done?

 

Look on the front of the xfer case for a silver/blur tag to ID it. Have you pulled the upper fill cap and made sure it is not way OVER full? Should uses 80/90 gear lube.

NP205 Rebuild Guide

NP205 New Process Transfer Case Diagrams and Information

Offroad Design - Complete Rebuilt NP205, NP203 transfer Cases

 

The only thing I can think of that would cause that if the fluid level is correct and the vent is breathing correctly. Where the rear housing bolts to the main case there is a small cutout for an oil drain back. It could be plugged up some how. Too much silicone from previous repair or just gunk from old oil. I ran in the rivers and creeks a lot so I ran my vent way up high. Be sure to check tranny level. The transfer case should be over full if tranny was leaking into transfer case.

 

I'd bet moose is right - check both boxes, I bet the Tcase is overfull and the tranny is low. While it probably should be fixed, dad had a chevy like that for 15 years, I "fixed" it with a couple hose barbs and a line up to the firewall.... But it wasn't a high-speed daily driver, either.