Tranny Problems?

[Liberator]

Here's the story! I just got the truck on the road again only to find that the transfer case is leaking automatic tranny fluid. Funny thing is, I had gear oil in the old NP205. So, it seems the input seal on the transfer case is bad. I dropped the transfer case and preped it for a rebuild. Then I began to ponder this question. Maybe the seal isn't bad! Is it possible something in the tranny is plugged and therefore building enough fluid pressure in the tailshaft section to push tranny fluid into the transfer case through a perfectly good t-case input shaft seal? I would like some opinions before I rebuild the t-case and stick it in only to find the tranny has problems. Besides, that cast-iron monster is hell to manuever in and out of the Blazer.

Thanks

 

[Liberator]

BTT

 

[imiceman44]

Since you didn't say which kind and your profile doesn't either, I will assume tranny fluid = auto.
Now to know if it's plgged and puking blow some air in the fill tube and wait and see if it pukes from there.
If there is no pressure build up, then the breather tube is fine and it should blow fluid through the seal if it's not bad.

 

[Liberator]

Thanks for the reply!

</font><blockquote><font class="small">In reply to:</font><hr />
then the breather tube is fine and it should blow fluid through the seal if it's not bad.

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I'm not exactly sure what you mean! I don't want to check if the breather/fill tube is plugged and I don't want automatic transmission fluid in the tailshaft of the transmission to get past the seal in the NP 205 transfer case which is running gear oil. I don't want to change the input shaft seal on the transfer case until I'm sure the tranny is not building enough pressure in the tail shaft to push auto-tranny fluid past the NP205 input shaft seal. Is this pressure build up possible in a TH350 and if so could the tranny fluid pressure in the tailshaft increase enough to get automatic tranny fluid past the input shaft seal on the t-case. I know nothing of the inner-workings of a TH350 transmission and would like to know if this pressure build-up is possible. Could anything other than a bad seal on the t-case cause the automatic tranny fluid to mix with the gear oil in the t-case? Pressure build-up maybe?

 

[imiceman44]

OK as you said you don't know much about trannies.
Reread my post, a tranny will build up pressure, that is why there is a breather so it releases the pressure from the top so only air comes out.
If this breather is plugged then it will take the easy way out, the seal or the fill/dipstick tube.
If the seal isn't great it's where the fluid will go since it's lower than the filler tube.
If the seal is tight, then the fluid will puke out from the tube.
/forums/images/graemlins/thumb.gif

 

[Liberator]

That must be where I'm lost. I don't know of a breather tube on a TH350. I thought the filler tube also acted as the breather. So based on the information you've given me, I need to be looking for a separate breather tube? Where on the TH350 is the breather tube located?

 

[imiceman44]

The breather tube is on top of the case, it's a niple with a plastic cap on it, or someone could have put an extension to it with a ruber hose.