ATF dripping off driveshaft, trans seal or transfer case seal?

[fordsucks!]

Th350 transmission with NP205. Any ATF I put in transmission, ends up on garage floor off the rear drive shaft. My local shop told me to pull the drive shaft and replace that rear seal, but to me it seems like it wouldn't the fluid be going into the transfer case? Or is it just slipping through on the shaft

The shop told me I don't have to pull transfer case, just replace the rearmost seal, but the guy was pretty drunk when he said this so wanted to get your opinions. The only videos I can find on YouTube are two wheel drives, nothing with the transfer case

 

[Wes Harden]

Yes is leaking from trans into t case. I bet you t case is over full, and your trans is low.
Np205 uses 80w90 hypoid gear lube.
1st thing to check is the trans case vent. If it is plugged up no seal will stop the trans fluid from being pushed into the tcase. I have fix a number of 2000s vintage fords, just by opening a clip that pinching the vent hose on the trans. Came that way from the factory. After draining and correctly filling the tcase no further repairs were needed.
So if your vent isn't clear and you clear it you might get lucky and not need a new seal.

If it is clear then, You'll need to do the seal in the adapter.

 

[fordsucks!]

Thank you for that tip, about to get underneath and check right now.

 

[fordsucks!]

I'll be damned, breather seems plugged. Either that or the hole on the nipple is really small. But last night I couldn't even get a small zip tie in the thing, seemed plugged.

After work in a couple of hours, I want to take a better look with the mirror and see what the hell is going on. So a plugged breather can cause fluid to leak? Man I really hope that's all I have!

 

[Wes Harden]

Yes the trans fluid expands, ie two lines on dip stick hot and cold. The air inside the trans must go somewhere. If it can't escape through the breather it will move into the t case, taking atf with it. The tcase fluid doesn't expand as much, less heat, so lower pressure.
Now would be a good time to check all the breathers t case and both axles.

 

[wazzabie]

This is why I run tranny fluid in the np205 tcase.

 

[Wes Harden]

spec is 80w90 unless it's a later Ford then atf. I don't get it both are New Process. I have used straight w50 before it works good.

 

[wazzabie]

spec is 80w90 unless it's a later Ford then atf. I don't get it both are New Process. I have used straight w50 before it works good.

On my 78 K5 I run a 72 NP205-th350 setup. I'm not sure if GM spec tranny fluid for the np 205. Either way if the seal goes bad there is cross contamintaion of the gear oil and tranny fluid. So for that reason to save my tranny I run tranny fluid in the np205.

 

[1-ton]

I run ATF in my NP205 as well. My square body is a later 88 - 91 which are speced from the factory for ATF. I believe the 73- 87 square body NP205 are speced for 80W-90 from the factory, but I think you can get away with running ATF in them if you want, in order to prevent cross contamination of gear oil and ATF. My NP205 had an ATF leak at the rear drive shaft output seal, but that was because the output yoke bolt had come a little loose, and allowed the yoke to slip back and forth enough on the seal to damage it.

 

[Wes Harden]

The seal would need to be very bad for t case oil to enter the trans. Or parked nose down for long periods.
Transmission makes way more heat, and pressure.
I do see your reasoning. The np205 is very robust, any lube is probably good enough.
Doesn't save on trail fluids either way.