Most likely source for leak between TH400 tranny and QT t-case?

[Frustrated]

My Jeep has had a leak at the tranny to t-case interface for as long as I have owned it (15+ years). I'm 99% sure the leak is there but it has been difficult to trace because my QT has been converted to part time and I run ATF in it. The leak is definitely coming from the tranny because it's empty and t-case is full.

I have had them apart a few times over the years and used permatex as a gasket but haven't been able to stop the leak. I pulled the t-case out again. I've cleaned both surfaces and am wondering what the cause of the leak is. There is ATF visible on the bearings on the tranny output shaft. There is no ATF inside the sun gear on the t-case where the tranny output shaft engages. The t-case front oil seals appear to be in good shape.

Any thoughts? Anybody have any luck with the Crown gasket vs. Permatex? If I do use permatex, where exactly on the adapter should I put it (there are some milled out areas on the t-case front face)?

[Frustrated]

My QT did not have this rubber o-ring on it. Could that also be part of the problem?



https://www.jeepforum.com/forum/atta...510_185549.jpg - direct link

[Frustrated]

Sorry Babywag, I accidentally erased my entire thread including your post while trying to edit.

So, if the forward most seal on the QT is damaged, ATF can get past it and then go out the weep hole?

[Frustrated]

Anybody know what seals are best. I've found Chicago Rawhide 13571 and Timken 5872s.

I also found a post on another site indicating the o-ring seal was only used from 1973 - early 1978. If this is the case and I don't have one then should I not use the one in the Crown kit (assuming it comes with it)?

[Frustrated]

Any consensus on whether or not I should use the o-ring and the gasket if my t-case didn't have the o-ring originally?

[Mike7009]

Are you talking about the o-ring that goes between the case halfs? If so some have it and some dont. I have one of each style.. it's pretty obvious if it takes it or not when you split the case. It will have a groove in the one half for the o-ring.

[Frustrated]

No - I'm talking about the o-ring between the tranny and t-case. It's in the pic posted above. My research shows that QTs between 1973 to early 1978 used it and then they stopped for some reason.

[Mike D]

the picture ws deleted with the thread too

[Frustrated]

You can't see the pic in the 2nd post of this thread? It shows up for me . . . let me know and I will re-post it.

[babywag]

Every QT that I've owned it was usually the 2 input seals.
Very easy to mess 'em up installing the QT.

If it doesn't go on straight or rubs on the seals while installing they will leak.
Can't have weight on seals and slide QT onto trans output shaft etc.

Short pieces of all thread or bolts w/ heads cut off and sliding case on helps w/ not damaging seals on install.

[Frustrated]

I think it's my seals also. I had the t-case off 2 times in the past 15 years and I know output shaft had to rest on the seals because I did the ole' bench press maneuver to put it on and off by myself when I was younger.

My seals were definely not set at the proper depth though. They were touching each other and the weep hole was blocked.

I have the Crown kit on the way so I will post pics of the seals to confirm the proper orientation.

[Mike D]

I dont see a picture in post #2 ...

looks just like this ....

[Frustrated]

OK - I provided a direct link and I downloaded the pic and put a copy in my photobucket account.

[Mike D]

OK .. so now were seeing a picture ...

I put a th400 from a chevy to a D20 and the tailshaft did not have a seal or a grove in it for an O-ring ....

I used a hand grinder clamped in a vice and strapped the tail housing down to the table and adjusted the position of all of it so that the grinder was barely touching the output shaft ... then with the grinder running i cut a shallow grove in the output shaft ...

All not very safe to do .. but i did not have any money for quality grinding ....

I did not use an O-ring ... i had a hard tinme getting one to stay on -- after talking to a CNC friend at the plant i worked at ... was suggested to use some high speed packing line .... it works like an O-ring but is like a waxed string and he guaranteed that the Trany fluid and gear oil would never eat it up ..... and that all i had to do was twist it apon its self on the shaft ...kinda like a fishing knot but not pulling the ends back on its self ... and pull it tight, cut the ends off close to the shaft and then drive the tail housing on to cut the packing line.

Its been like that for over 18 years and i don't have odd colored T-fluid ... and some day ill check the D20 gear oil ....

Iv not put alot of miles on it .... some day maybe ... and i still need to get a bottoming tap on the tail shaft -- for the bullgear bolt (the one that gets bolted to the end of the tailshaft that came from the original T90) ... i don't feel confident that there are enough threads to hold it well ... but its been "for ever" on there like that and not destroyed its self yet ....

Ok .. so that's a long story .. an O-ring would probably be cheaper in the long run ....

[mokurt]

Anybody know what seals are best. I've found Chicago Rawhide 13571 and Timken 5872s.

Both of those are quality brands,National is another.

I would avoid made in China.