2006 Allison converter housing leak, stumped. Ideas?

thunder550

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Apr 2, 2013
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Been chasing a leak from the converter housing area in the 2006 LBZ truck I bought in Sept 2020. Trans has been out 4 times, and still leaking. Leak presents externally by dripping out the small round inspection cover hole on the bottom of the converter housing. When I stick my borescope up inside, I am finding transmission fluid around the bolt heads that hold the pump to the converter housing. At this point I am not sure if it's coming from the bolt holes or somewhere else...more on that below.

I am not sure if it's coincidence or due to the extra heat and/or distance, but I have only been noticing new fluid under the truck after towing.

I've pulled the trans twice, finally gave up and took it to a local diesel shop who has also now pulled it twice, the second time under warranty. Pump plate gaskets, pump o-ring, bolt head o-rings, converter snout seal, copper washers, pump and housing bolts have all now been replaced multiple times. RTV around all bolt heads. On the last attempt, I had the shop replace the whole converter housing with a new one, thinking that maybe there was a tiny crack or something somewhere that we couldn't see. Just got back from a trip towing our 5th wheel and checked underneath....still leaking :mad:

The only thing that I can think of that's left to replace is the torque converter itself. It's a stock converter, and if it's original (which I think it probably is), with 260k miles on it. The only reason I haven't done this yet is because I am only seeing fluid on the face of the converter housing where the pump bolts to...I would think that if the converter itself was leaking somewhere that it would be slinging fluid all around inside the housing...but I suppose anything is possible at this point.

So...I'm stumped, the shop is stumped...does anyone have any ideas? My next step would be to replace the converter, but I'm getting tired of throwing parts at this thing just to see what happens.
 
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thunder550

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Apr 2, 2013
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Here's what I'm seeing this morning after our weekend trip.

PXL_20210510_145826178.jpg

Here's what the inside typically has looked like previously. I haven't had a chance to get under yet today and see if it looks the same. The fluid is collecting around the bolt heads....it looks like at first glance that it's coming from under the heads, but maybe it's coming from somewhere else and just collecting there?

received_1223968931392075.jpeg

received_432516941175258.jpeg
 

2004LB7

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Dec 15, 2010
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Norcal
Is this the same transmission as you posted in this thread?

 

clrussell

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Sep 23, 2013
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I’ve had the same issue on two trucks. Replaced converter and it was fixed.
I hope it takes care of yours
 
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thunder550

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Apr 2, 2013
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Is this the same transmission as you posted in this thread?

Yes, the same one.

I’ve had the same issue on two trucks. Replaced converter and it was fixed.
I hope it takes care of yours
Converters leaking without slinging fluid everywhere?
 

clrussell

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Sep 23, 2013
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Mine looked like yours. Wet on the lower half of the bell housing. I put a front seal in the truck only to have to put a converter in it soon after because it still leaked.
 
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thunder550

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Apr 2, 2013
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Would it not be wise to just continue your previous thread so others can see the history and what was already tried?
That thread title doesn't accurately represent the content, and rather than have people read through a bunch of posts I thought it would be easier just to state in a couple sentences that everything exposed to the inside of the converter housing has been replaced (some multiple times) except the pump and converter.
 

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