Any quick-fix for hairline crack in pipe thread?
#2921640
05/12/21 12:54 PM
05/12/21 12:54 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
OP
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OP
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Joined: Apr 2006
Posts: 4,220
West Plains, MO
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I have a BW1356 transfer case (that's still in the truck). Some previous gorilla overtightened the pipe plug in the drain hole, causing a longitudinal hairline crack in the boss. It doesn't extend radially into the case itself, but when the plug is tightened down with Teflon tape, it spreads the crack just enough to cause a slow annoying drip. I tried cleaning the area and using Hylomar sealant before reinstalling the plug, but it still seeps. Someday I will take it off, remove that cover, and fix it properly. In the meantime, is there any quick-fix, or at least something that can be done without removing the t-case? It is a real PITA to R&R it. The case is magnesium alloy so welding is not an option (certainly not while it's on the truck!)... drilling the crack is not likely to work because the pipe thread will just spread apart again. I think I already know the answer here but still hoping. Maybe JB Weld?
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Re: Any quick-fix for hairline crack in pipe thread?
[Re: jcastle1]
#2921951
05/13/21 12:12 AM
05/13/21 12:12 AM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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OP
master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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If the case is aluminum, you should never use teflon tape. That's most likely why it cracked in the first place. Take the tape off, tighten the plug, smear black RTV around it and cover the crack. Let it sit overnight and should have no more leaks. It's not aluminum, it's magnesium alloy, as stated. And Teflon tape does not cause cracks, overtightening tapered threads in soft material does... And I didn't crack it! It was cracked when I got it (without tape) but severely overtorqued. I really had to lean on it to get it unscrewed. What size pipe thread. Some share the same thread dia. and pitch as common straight thread bolts. If so you might be able to run a straight tap thereby eliminating the taper that is spreading the case. I would then use blue loctite or similar thread sealant and call it good. I thought about drilling and straight-tapping it, then using a matching plug with an o-ring head. It's been a while since I got under there but I believe it's 1/2" NPT which is 14 TPI. Unfortunately 1/2 UNC is 13 TPI...
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Re: Any quick-fix for hairline crack in pipe thread?
[Re: DrCharles]
#2922618
05/14/21 09:11 PM
05/14/21 09:11 PM
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Joined: Jan 2003
Posts: 15,348 Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,348
Omaha Ne
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If the case is aluminum, you should never use teflon tape. That's most likely why it cracked in the first place. Take the tape off, tighten the plug, smear black RTV around it and cover the crack. Let it sit overnight and should have no more leaks. It's not aluminum, it's magnesium alloy, as stated. And Teflon tape does not cause cracks, overtightening tapered threads in soft material does... And I didn't crack it! It was cracked when I got it (without tape) but severely overtorqued. I really had to lean on it to get it unscrewed. What size pipe thread. Some share the same thread dia. and pitch as common straight thread bolts. If so you might be able to run a straight tap thereby eliminating the taper that is spreading the case. I would then use blue loctite or similar thread sealant and call it good. I thought about drilling and straight-tapping it, then using a matching plug with an o-ring head. It's been a while since I got under there but I believe it's 1/2" NPT which is 14 TPI. Unfortunately 1/2 UNC is 13 TPI... They do make non tapered pipe fittings and taps, they are referred to as NPS vs. NPT NPS fittings use an Oring for sealing but in a non pressure application I would try Teflon tape/ paste or Loctite blue
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