4R70W filling Transfer case with ATF

[DRBRONCO69]

Hey Trans guys,
I've got a 4R70 W in my street truck that keeps losing fluid. Apparently it's filling the transfer case with ATF to the point that it now blew out of the vent and the rear output shaft seal on the transfer case before I figured this out due to being completely overfilled. Now that everything is covered in trans fluid, I power washed it all off, degreased everything and drained the excess ATF from the transfer case. My question is, What seal would cause this issue? Does the 4R70W have an output shaft seal as well as the NP205 input shaft seal to keep the two from swapping fluids or is it just the one NP205 Input shaft seal that will need to be replaced? I've read some conflicting answers on some Ford Truck forums about some split ring seal on the 4R70W. I don't remember seeing any sort of seal in the back of the 4R70 housing when I mated it to the 205 Case. Thanks!

 

[EPB72]

99%sure it’s only a seal in the transfer case and paper gasket between the 2.. just did a 02 f150 and that’s it was ..

 

[rjrobin2002]

I've seen this when people use the 4x4 4r70w with a dana 20 and you have to add a seal to the ZF adapter. But I thought on the NP 205 the T case had an input seal.

 

[rjrobin2002]

That's a heavy transfer case to pop off and check, LOL

 

[DirtDonk]

Did you do the conversion or did you buy the bronco with it already done?

 

[Broncobowsher]

You are going to have to pull the transfer case anyway. Then you just look for where the seal is at.

 

[Wes harden]

Make sure the transmission vent and any hose attached are clear and open. If it is plugged when the trans get hot and builds pressure it will force trans fluid past that seal into the t case new or not. I have seen this many times.

 

[DRBRONCO69]

Did you do the conversion or did you buy the bronco with it already done?

I did the conversion, the NP205 is bolted directly to the 4R70. It had a seal on the input but the transfer case was used and I didnt replace it.

 

[DRBRONCO69]

Thanks guys, I'll check the vent on the trans but I am 99% sure that it is good because it all came directly from the Mountaineer and it didn't have any issues until I put the NP205 behind it. The Mountaineer was running and driving perfectly without leakage. Sounds like I've gotta pull the T-Case and replace the input seal.

 

[Yeller]

I've seen a lot of 205's with the incorrect input seal. The parts store book shows a single lip seal, the correct seal has a lip and spring on both sides of the seal, that can be difficult to source. The easy solution is 2 of the single lip seals installed back to back. I've also had bolts in the bearing retainer come loose and do the same thing. This really is a fairly common issue. At least there are no parts in the 205 that are harmed with excessive amounts of ATF, just drain and refill.

 

[spap]

I had a c4 that leaked into the Dana 20, and I never seen a transfer case so clean on the inside afterwords.

 

[DRBRONCO69]

I've seen a lot of 205's with the incorrect input seal. The parts store book shows a single lip seal, the correct seal has a lip and spring on both sides of the seal, that can be difficult to source. The easy solution is 2 of the single lip seals installed back to back. I've also had bolts in the bearing retainer come loose and do the same thing. This really is a fairly common issue. At least there are no parts in the 205 that are harmed with excessive amounts of ATF, just drain and refill.

Like this one?

https://www.transmissionpartsdistri...43-np247-np249-transfer-case-input-seal-4435/

 

[Yeller]

yes that is the correct seal.