Weepy gearbox drain plug

[Carmudgeon]

Gearing up to do a fluid change on a gearbox with a weepy drain plug that has long had a tendency to get moist, but never to the point of spotting the floor.

Teflon tape had served to keep that at bay, at least until now, so gonna try something different this time, a thread sealant.

I see the high-temp version with PTFE has gotten the nod in the past, but am curious as to whether the regular version would suffice as well?

And as far as application goes, how sensitive is it to residual gear oil (ATF), or needing the "activator" spray?

I can clean the threads on the case as best I can, but it's one of those situations where fluid will still dribble out unless it's left to drain for days, and that's not really a practical thing, or is it a clean room situation. The 24 hour cure time is doable.

 

[B1974]

I'd try a new plug or more Teflon tape.

 

[clinebarger]

Hylomar M & Permatex aviation form a gasket works pretty well.

Sometimes it goes way more in-depth than sealants, The plug &/or the receiving threads in the case could be compromised.

Brass NPT plugs are so wild in their dimensions than it can be used to an advantage, Find an oversized one & clean up the case threads with a Tap.

 

[B1974]

What type of vehicle is this? aluminum case or steel?

 

[ArcherDriver]

Gearing up to do a fluid change on a gearbox with a weepy drain plug that has long had a tendency to get moist, but never to the point of spotting the floor.

Teflon tape had served to keep that at bay, at least until now, so gonna try something different this time, a thread sealant.

I see the high-temp version with PTFE has gotten the nod in the past, but am curious as to whether the regular version would suffice as well?

And as far as application goes, how sensitive is it to residual gear oil (ATF), or needing the "activator" spray?

I can clean the threads on the case as best I can, but it's one of those situations where fluid will still dribble out unless it's left to drain for days, and that's not really a practical thing, or is it a clean room situation. The 24 hour cure time is doable.

I would try Aviation non-hardening Permatex. Also, the suggestion to try more Teflon tape seems very logical.

 

[Lubener]

Since you state it never spots the floor, I would try a new plug and gasket. Other than that, I wouldn't worry about it if the condition doesn't worsen.

 

[Kira]

Permatex "Ultra Black" is the one I've used with success. Damaged Honda oil pan was the worst....that one did drip.

 

[Trav]

+ On Hylomar on the cleaned threads.

 

[doitmyself]

My 2 cents, I've used Permatex #2 Form a Gasket on weepy plug gaskets. With any of these thread lubricants, be careful not to over tighten the plug.

 

[John105]

First time I drained the trans and filled it, I wasn't aware of the thread sealant being needed, although it dawned on me, the plug does not seat the way a drain plug does. So it dripped. If you can believe it, a new plug was cheaper than sealant, so I bought new plugs at rock auto for around $2.75 each, like 6 of them. Second time I did it, I used a new plug again. It has some yellow stuff already on it. I guess I avoided the research needed to figure out what OP wants to know...

 

[Carmudgeon]

Thanks all.

The gearbox in question is a Getrag 5-speed, with an aluminum case, in an old BMW.

It uses M24x1.5 drain/fill plugs, with no gaskets, just the face of the plug against the casing, and half the thread depth on the plug never even comes into use. One of those standard/universal parts whose applications span decades within an OEM's catalog. Not sure if it has ever been revised for better performance, but I can look into it. I've read that overzealous torquing of the plugs can crack the case, but I don't believe that's the situation, but I guess I'll find out and cross that bridge if needed.

My only experience with a Hylomar-type sealant was on a thermostat housing, and it's neat stuff. Is there a big practical difference between the more readily-available "blue" and "M" varieties?

On the whole, I've been pretty lucky in my DIY life to not have troublesome leaks, need aids, or have to address mangled threads, so this is kinda new to me. The teflon tape has worked in the past, but it's weeping like never before, so I don't know whether this application is just past due, or other factors are at work, but I do want to avoid the nightmare of running the thing dry. I'm assuming a much smaller margin for error in a gearbox with a quart of fluid, than a slushbox that takes a case of fluid.

 

[elansprint]

Thanks all.

The gearbox in question is a Getrag 5-speed, with an aluminum case, in an old BMW.

It uses M24x1.5 drain/fill plugs, with no gaskets, just the face of the plug against the casing, and half the thread depth on the plug never even comes into use. One of those standard/universal parts whose applications span decades within an OEM's catalog. Not sure if it has ever been revised for better performance, but I can look into it. I've read that overzealous torquing of the plugs can crack the case, but I don't believe that's the situation, but I guess I'll find out and cross that bridge if needed.

My only experience with a Hylomar-type sealant was on a thermostat housing, and it's neat stuff. Is there a big practical difference between the more readily-available "blue" and "M" varieties?

On the whole, I've been pretty lucky in my DIY life to not have troublesome leaks, need aids, or have to address mangled threads, so this is kinda new to me. The teflon tape has worked in the past, but it's weeping like never before, so I don't know whether this application is just past due, or other factors are at work, but I do want to avoid the nightmare of running the thing dry. I'm assuming a much smaller margin for error in a gearbox with a quart of fluid, than a slushbox that takes a case of fluid.

I'm assuming this isn't one of the Getrag 260 or related gearboxes? Just curious since your description of some of the thread remaining unused makes it sound like the 70s/80s plugs but those don't have a face which contacts the outside of the case as far as I am aware. Like this:

 

[Carmudgeon]

I'm assuming this isn't one of the Getrag 260 or related gearboxes? Just curious since your description of some of the thread remaining unused makes it sound like the 70s/80s plugs but those don't have a face which contacts the outside of the case as far as I am aware. Like this:

A later 220 series that uses these plugs. They bottom out well before the threads are fully consumed.