Do you use anything to seal the gearbox drain plug?

[ladaspeed]

Mine has been overtightened and has cracked the housing, its no drama as I have a spare gearbox and can pilfer the bits from that.

I suspect it was overtightened to try and seal it a bit tighter, It might even have been me who did it, or at least got it to the point where the crack opened enough to be more than an occasional drip.

So do you use anything to seal it so there is no need to crank it up super hard?

 

[kmead]

It is a pipe thread so technically no sealant required. That said, one can easily use a sealant. I tend to use a non hardening version of Form A Gasket. I use a thin amount to fill the threads so it doesn’t squeeze out and float around in the transmission.

 

[Dan Sarandrea (Phila)]

In some situations soldering the crack would work, but you're fighting a huge mass of aluminum that's just going to pull the heat out of the area, so maybe not the best choice.

How about draining the gear oil, fanatically cleaning the area (and possibly the crack) with a residue free solvent, then use a wicking-viscosity super glue and hope the glue sucks itself into the crack?

Loctite 406 Wicking Viscosity Cyanoacrylate Instant Adhesive

Shop Loctite Prism 406 cyanoacrylate a wicking viscosity super glue that will bond very well to most materials. Loctite 406 is a surface insensitive cyanoacrylate.

www.dispensing.com

 

[Rupunzell]

Mine has been overtightened and has cracked the housing, its no drama as I have a spare gearbox and can pilfer the bits from that.

I suspect it was overtightened to try and seal it a bit tighter, It might even have been me who did it, or at least got it to the point where the crack opened enough to be more than an occasional drip.

So do you use anything to seal it so there is no need to crank it up super hard?

Bane of tapered "pipe" threads, they have this behavior of tapered external threads WAY over stressing the internal threads causing cracks and more.. Add to this problem, there is a horrid tendency for wrencher folks to WAY over torque any tapered threaded fittings almost always causing cracks and more related damage. The way to prevent this, use teflon sealing tape or teflon sealant paste... Do Not Over torque due to the fear of leaking.

Once the internal threaded boss has been cracked, the fix is very messy. Proper fix means drilling the apex of the crack, grind out the cracked area, bake out the oil, do the weld up, then comes the most "fun part" re-do the internal threads. Ideally, this would be done with a slightly over sized straight internal thread with a faced flat area on the outside for a straight thread plug with a sealing washer.

There are no easy fixed like apply some "adhesive" that will be a secure and sure fix due to the amount of force produced by the tapered threaded fittings.

If the housing is replaced, know the housings are made as matched sets that _might_ interchange. If the work is done for a housing swap, may as well move all the oily bits over to the known good housing set. BTW, check the reverse gear idler shaft boss on on the front housing (engine side) as that boss has a tendency to crack due to abuse of the reverse gear.


Bernice

 

[ladaspeed]

Bane of tapered "pipe" threads, they have this behavior of tapered external threads WAY over stressing the internal threads causing cracks and more.. Add to this problem, there is a horrid tendency for wrencher folks to WAY over torque any tapered threaded fittings almost always causing cracks and more related damage. The way to prevent this, use teflon sealing tape or teflon sealant paste... Do Not Over torque due to the fear of leaking.

Once the internal threaded boss has been cracked, the fix is very messy. Proper fix means drilling the apex of the crack, grind out the cracked area, bake out the oil, do the weld up, then comes the most "fun part" re-do the internal threads. Ideally, this would be done with a slightly over sized straight internal thread with a faced flat area on the outside for a straight thread plug with a sealing washer.

There are no easy fixed like apply some "adhesive" that will be a secure and sure fix due to the amount of force produced by the tapered threaded fittings.

If the housing is replaced, know the housings are made as matched sets that _might_ interchange. If the work is done for a housing swap, may as well move all the oily bits over to the known good housing set. BTW, check the reverse gear idler shaft boss on on the front housing (engine side) as that boss has a tendency to crack due to abuse of the reverse gear.


Bernice

I will have to compare the housings, I can already see the fill plug is in a different position. Plus it is a tripode output not a cv. Which means paying attention to the shims/backlash on the output bearings as well... The drivetrain is all disconnected and ready to drop so I will know this weekend.

If I have to use the existing housing I will get it welded up, I am in NZ and there is a strong culture of repair, and a lot of experience with this sort of thing.

Also the idea to cut a straight thread and sealing face after welding is an excellent one...

 

[Dr.Jeff]

I have found both tapered thread and straight thread plugs on X's. I believe the holes (engine oil pan and trans case) are actually a straight thread - hopefully someone can verify that. But I've seen drain plugs on X's that use a copper washer to seal its lip (on straight thread plugs), which would not work on a tapered thread hole. So it might be worth confirming what you have. However it really doesn't matter what type of plug you have if the case is cracked, the damage is already done.

 

[ladaspeed]

Hmm

 

[ladaspeed]

I got it welded up, and it turns out both the holes were tapped parallel and fitted with taper plugs, so the crack is probably to be expected. Fortunately I had the correct M22x1.5 tap and some threaded rod, so I modded things. The only downside is that it wont completely drain, but its not like I'll be doing another 100,000kms...

 

[Dr.Jeff]

turns out both the holes were tapped parallel and fitted with taper plugs

This is exactly what I was talking about earlier. A straight thread plug with a sealing washer (like you now have) is correct for these cases in my opinion. But most of the time I find they have tapered plugs installed (like you had). And most Fiat specialty vendors sell tapered replacement plugs.

Fortunately other vehicles use the same size drain plug, and can be purchased with a magnet for added protection:

CNC Aluminum Magnetic Oil Drain Plug/Bolt M22X1.5 For Motorcycle KTM Ducati | eBay

Giving more protection to your motorcycle engine with this CNC Magnetic Oil Drain Plug/Bolt. Pre-Drilled for Safety Wire. -- Qty: 1x Magnetic Oil Drain Bolt. -- Press fit Power Magnet on the drain plugs.

www.ebay.com

 

[kmead]

This is exactly what I was talking about earlier. A straight thread plug with a sealing washer (like you now have) is correct for these cases in my opinion. But most of the time I find they have tapered plugs installed (like you had). And most Fiat specialty vendors sell tapered replacement plugs.

Fortunately other vehicles use the same size drain plug, and can be purchased with a magnet for added protection:

CNC Aluminum Magnetic Oil Drain Plug/Bolt M22X1.5 For Motorcycle KTM Ducati | eBay

Giving more protection to your motorcycle engine with this CNC Magnetic Oil Drain Plug/Bolt. Pre-Drilled for Safety Wire. -- Qty: 1x Magnetic Oil Drain Bolt. -- Press fit Power Magnet on the drain plugs.

www.ebay.com

And set up for safety wire no less.

 

[ladaspeed]

This is exactly what I was talking about earlier. A straight thread plug with a sealing washer (like you now have) is correct for these cases in my opinion. But most of the time I find they have tapered plugs installed (like you had). And most Fiat specialty vendors sell tapered replacement plugs.

Fortunately other vehicles use the same size drain plug, and can be purchased with a magnet for added protection:

CNC Aluminum Magnetic Oil Drain Plug/Bolt M22X1.5 For Motorcycle KTM Ducati | eBay

Giving more protection to your motorcycle engine with this CNC Magnetic Oil Drain Plug/Bolt. Pre-Drilled for Safety Wire. -- Qty: 1x Magnetic Oil Drain Bolt. -- Press fit Power Magnet on the drain plugs.

www.ebay.com

Tbh I think I will find a replacement gearbox, there were some obvious issues with this one. If it lasts another couple of years I'll be happy.

 

[Dr.Jeff]

By the way, your user name (ladaspeed) reminded me, you can buy a magnetic M22(1.5) drain plug from the online Lada parts supplier quite inexpensively. However it is a tapered plug, not a straight thread one. They also sell a non-magnetic version for even less $....which is what I suspect the common Fiat specialty vendors are re-selling at a substantial markup (identical pics in their listings).