Need to replace drain plug on 1356 t-case. Galvanic corrosion?

[MtnHaul]

So somebody in the past has slightly boogered up the drain plug on my 1356 t-case, but thankfully I was able to loosen without further damage--why do people put those things in so damn tight? Anyways, I want to replace the drain plug and was wondering if galvanic corrosion is much of a concern here or am I just overthinking things? I do use PTFE paste on the threads when reinstalling the plugs so that may delay/reduce corrosion. So far I cannot find a replacement magnesium plug but the search continues.

 

[XOLATEM]

Is it straight threads or pipe theads....? I can't remember...

But...it would seem that using the pipe thread sealer would fix any potential problems...just use anything that will fit...

why do people put those things in so damn tight?

Fear of leaking is a powerful motivator...especially when they don't hold a lot of fluid...

am I just overthinking things?

Don't be fearful of this tendency...it will keep you busy and entertained at worst and out of trouble at best...always worked for me...

Just my .02...

 

[MtnHaul]

Yeah I just went with some brass pipe plugs so at least there's more to grab onto should things get tight. I guess when I was first started teaching myself how to perform automotive repairs I learned early on that "tight enough" actually was tight enough and that every fastener/threaded item need not be torqued until it can't be moved any further. But we all learn at different rates.

 

[franklin2]

Be careful. They are tapered pipe threads. If you get it too tight you can crack the magnesium case and you will have a constant irritating oil leak.

I had to repair one for a guy, I had to take a file and file the crack to open it up, and the put jb weld on the crack and put the plug back in it and let it dry. I fixed the leak but then kicked myself afterward, I should have put a pipe hex bushing in with the jb weld and then put a smaller pipe plug in that.

But that truck is still running, he never changed the oil in the transfer case anyway. If anyone tries they are going to get a big surprise.

 

[nelstomlinson]

There is potentially salt and water on the outside of the gear case, so I guess there is potential for galvanic corrosion. I wouldn't use a brass plug in an aluminum or magnesium case. Steel is going to be less damaging if there is any galvanic action. Some thread dope might help, can't hurt.

 

[nelstomlinson]

Epoxy doesn't handle heat well. Heat that plug a bit with a torch and it'll come right out. Heat the magnesium enough and you can have a Class D fire, for extra excitement!

 

[MtnHaul]

There is potentially salt and water on the outside of the gear case, so I guess there is potential for galvanic corrosion. I wouldn't use a brass plug in an aluminum or magnesium case. Steel is going to be less damaging if there is any galvanic action. Some thread dope might help, can't hurt.

Good call on the steel vs brass. I found a chart that explains the difference in compatibility and I can see how both brass and steel are far removed from magnesium but steel is closer and a better choice between two less than ideal options.

 

[typ4]

I've had steel in mine for 20 years

 

[XOLATEM]

Heat the magnesium enough and you can have a Class D fire, for extra excitement!

Yeah, I would be careful with that...once you start a magnesium fire...you can't put it out...even dunking it in water...it makes its own oxygen...

That is one reason I was scratching my head on WHY did the OEM's use this material...aluminum was fine...and probably less expensive...

 

[snicklas]

I think they started using Magnesium because it is lighter and stronger. It’s actually in more places in a vehicle than you might think. When I was on the FD we had training on it, because water+mag=REALLY BAD. If I remember (this was 15+ years ago) there are at least a couple BMW models that the support structure under the desk is mag…. Car Fire and Water to put it out makes an “explosion”. There are videos out there of it.

There have been a couple of fires at plant that use mag, and if they catch fire, you have to let them burn themselves out.

Also, fun fact, on the the ingredients in the bright white flares, is magnesium. Mag burning seems as bright, or maybe brighter than welding…..

 

[MtnHaul]

Locally I can't find a plain steel plug--only brass or galvanized. Any reason to not use the galvanized? Shouldn't the zinc coating slow any corrosion? I could always just burn off the coating with a torch. I'm trying to avoid ordering from McMaster-Carr because I'll end up ordering a bunch of extra stuff too!

 

[XOLATEM]

I could always just burn off the coating with a torch.

don't breathe the fumes from that...zinc...

 

[nelstomlinson]

Galvanized is better than plain steel, check your galvanic table.

 

[MtnHaul]

don't breathe the fumes from that...zinc...

I'm careful around zinc--welder's sickness I think I've heard it called. I did once make a smoker out of a galvanized garbage can, but I burned off most of the coating and seasoned it by smoking a bunch of greasy bacon.