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Leak on my np203 adapter Need help quick

chevy111

chevy111

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My 74 has a 203 tcase and a th350. I just yanked them and had the tranny rebuilt. I also had the tcase freshened. I just finished installing them and getting everything started when a puddle of tranny fluid forms on the ground. I get under there and it is coming from the front of the adapter where the tranny bolts to it. It has 4 bolts that bolt the adapter to it and I am pretty sure I tightened them down good. Of course the only way to get to them is pulling the tcase back. I also remember installing the O-ring gasket between the adapter and tranny which was also new. I am going to tear it back apart tomorrow to see why its leaking. Has any one else dealt with this? Should I use a torque wrench on these 4 bolts to make sure they are perfect? It really sucks to have to take that big a$$ tcase out again.
 
if its tranny fluid its got to be from your trans rear seal, nothing should be in that adapter, and the t-case should have motor oil in it i believe, but definitly not trans fluid.
 
I Have never heard of a transfer case with motor oil in it. I have always had tranny fluid or gear oil in mine.
 
FIgured out why its leaking. One of the bolts on the tranny is bad. Somehow it stripped the threads when I tried to torque it down. Im thinking now I probably am going to need to drill it out and fix it.
 
stephan.laun said:
I Have never heard of a transfer case with motor oil in it. I have always had tranny fluid or gear oil in mine.
Click to expand...

yeah the 203 boat anchor takes motor oil. when i first got one i thought someone put the wrong crap in it
 
More like a ship anchor I would say.
I put 10/40 in it. Just got it back together and its working great. Man it was a real job to put that thing in. I think if I ever have to do that again I would put in a smaller t-case. I dont hardly ever 4 wheel it. I took it out tonight and its driving great. Maybe a 241. I heard those are alot lighter. I just found out I am moving too and I might be selling it. What a jiff because I just spent $1500 rebuilding everything. Oh and if you ever do this make sure to have a good jack for this purpose. I had a tranny jack and it was about half help.
 
Ancient thread but today after sitting for about 2 months. I drained the 203 and I swear after all the oil was done draining. There was some ATF coming out of the 203 drain hole. I noticed a drip coming down from the adapter.

Everything is new on the TH350 even the O-ring on the tranny/Tcase adapter.
The truck has been sitting so I’m sure all the ATF in the torque converter is filling up everything.

To the point I’ve spent an hour searching around online and nobody really has an answer other than the TH350 adapter seal is either bad (its brand new) or the little hole in the TH350 is letting the tranny fluid fill up and flowing through the shaft seal on the 203.


I just put The 203 in. Do I need to remove and fix the 203 shaft seal, or the TH350/w203 seal? Or can I leave it and just monitor tranny and Tcase levels?

Can the oil from the Tcase mix and get back into the TH350?
 
there is the seal on the 203 input gear that keeps the 2 apart . then some little amount of thread sealer on a few adapter to 203 bolts that are threw holes in to the gear oil side of the 203 .

also there should be little o-ring seals under the 4 bolts for the 203 adapter to the back of the th350 trans . and the bolts are a special washer head bolt and smooth sided to let the little o-rings seal up to them .
 
sweetk30 said:
there is the seal on the 203 input gear that keeps the 2 apart . then some little amount of thread sealer on a few adapter to 203 bolts that are threw holes in to the gear oil side of the 203 .

also there should be little o-ring seals under the 4 bolts for the 203 adapter to the back of the th350 trans . and the bolts are a special washer head bolt and smooth sided to let the little o-rings seal up to them .
Click to expand...

Yes,
Adapter bolts have sealer
New Orings under those 4 bolts.
New Oring on 203/th350 adapter

Maybe the input shaft on the 203 is where it’s seeping into.

——-Do I need to pull the 203 or what is the coarse of action?
Can I leave it, and just not let it sit so long. The oil I drained from the 203 today had no ATF in it.———


It drained through the night and so saw the drip under the adapter and drip forming on the hole where I drained the 203.
 
I know it’s an old thread from 11 years ago.
Just wondering what my course of action is.
 
most i can say is someone isnt happy and wants some quality time spent on it . . . could be the input seal / input seal holder gasket to range box / or the others who knows . might be dropping it again to check and find out .

and ATF loves to leak if the surfaces are not 100% atf free/dry when put together .
 
Ugh...
Ok...
So with that said. Can I still run it as is in the meantime and just keep an eye on fluid levels?

Everything was clean and dry before being put back together. I figure it’s because it’s been sitting for over a month. ATF in my experience always finds the weak points, may take some time but it finds them.

I hate that red fluid... hate it.
 
Last edited:
i ran a 205 for over 2 years leaking atf in to it . keep an eye on atf level and when you add 1 drain that much from other or till level is correct .
 
sweetk30 said:
i ran a 205 for over 2 years leaking atf in to it . keep an eye on atf level and when you add 1 drain that much from other or till level is correct .
Click to expand...

Thank you....
I’m going to fix up the other 203 just in case. I’ll run it, and check it. Drain some, fill some.

There is no way for the 203 oil to get into the TH350 and ruin it, is there?
 
if the input seal is BLOWN the heck out and you fill up the t-case to much yes it possibly could get back in the trans . and reg oils or gear oil in a auto is NOT good . altho some auto trans are built to run engine based oil but thats HUGE truck stuff or other equipment not out th350/400/700r4 units .
 
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