Rear diff drain leaks

[jboomer]

I went ahead and attempted adding a drain to my 9" rear today and it didn't go so great. First hole I drilled missed the internal compartment completely. Re-drilled next to it and a little higher and hit the compartment, however the case is only about an 1/8" thick. I bought a 1/8" 27 NPT tap and a brass plug, however that fine of a pitch just pulled right through and screwed up the hole. I was able to tap it with a 3/8" 16 though and bought another plug for it. Now, even with pipe tape on the plug, it's still leaking. The plug seats really tight, it just won't quit leaking though.

I was under the impression from another thread on this that I could do it without pulling the rear end completely out. What are my options to fix this? I don't know if RTV will stick to it or not...or if that's even an option. Am I going to have to weld it shut? I don't want to go to a bigger plug, because then the pitch just gets bigger which would make it worse.

Here's one of the few threads I referenced for doing this:
http://classicbroncos.com/forums/showthread.php?t=115941&highlight=rear+drain

 

[Revelation]

Without pulling the 3rd member I think your options are limited.
If it were mine I would weld a nut, or a 1/4" thick piece tapped, with the thread I wanted to use, over the current hole, maybe even enlarge the current hole a little. And while I had the welder out i would go ahead and fill in the first attempt to drill, wire brush the welds and paint. Be sure to connect the ground to the housing, not the 3rd member or axle as the is could cause pitting on the bearings.
(Note on the welds, if you are going to post pics of the completed project be sure your welds are good, or ground smooth so you do not have to hear about "Booger Welds")

 

[Viperwolf1]

Got a picture of where you drilled it? I had the diff out when I put mine in. That's how I decided just where to put it. This spot on my housing is more than 3/8" thick and it doesn't leak. I used a 1/8" pipe plug and it sits flush.

 

[jboomer]

VW-My second attempt was almost exactly right where yours is, maybe a smidge higher. It's definitely not 3/8" thick there though.

Rev-that's a legit idea. I was hoping there was a much easier way! If that's the route I go, I'm not posting any pics because ALL of my welds are "booger welds". However, is the intent here the bolt be long enough to prevent leaking? The plug screws in fine, albeit only 3 or so threads 'bite'.

 

[broncnaz]

Sounds like you may have used to big of a drill for the tap. Aside from that you can use teflon tape on the plug to help seal the leak.

 

[Viperwolf1]

Here's a pic from the inside. You can see how the housing edge is folded, then the cover is welded on top of that fold. You must have caught it up above the fold.

 

[GrillMaster]

Could you add a soft/brass washer to help it seal?

 

[Hoppy]

without pulling the diff a temp fix might be some Teflon tape or pipe dope
you might also try going to a bigger bolt. I'd assume you would need a larger tap to pull that off.

 

[malcolmzilla]

Av sealer.

 

[jboomer]

I went with Revs idea. Having some trouble with weld being porous and seeping fluid. I've got to look at it again in a little bit to see if I fixed it yet.

 

[jboomer]

What's "av sealer?". I've tried Teflon tape, no dice.

 

[Skiddy]

(Note on the welds, if you are going to post pics of the completed project be sure your welds are good, or ground smooth so you do not have to hear about "Booger Welds")

hey what you talkin bout;D

 

[malcolmzilla]

Aviation sealer, i might have the vernacular incorrect? Its thick black gooey smelly stuff that sets up very firm, resolved a coolant seep for me that thread tape could not.

 

[WyleCoyote]

I would pull the third member and do it again - it's really easy to pull the third - 5 lug nuts and 4 bolts per side, then the nuts around the third and you don't have to worry about screwing up your gears/bearings from welding.

What I did was weld a piece of 1/4 plate to the bottom then drilled through that and tapped it for 3/8 NPT and put a allen head inset plug in it. Doesn't seem to leak at all.

 

[DAKOTA7720]

You might also try the yellow pipe dope used for natural gas pipe. It is a thicker consistency than teflon dope.