Do NOT overtighten your transmission drain bolt! (Carnage included)

Learn from my idiocy and ONLY use a torque wrench when tightening your transmission drain bolt, or else the pic below can happen. Did this using a hand tool, not a power tool, and THOUGHT I was doing it with a light touch.


This is from the manual transmission on my 98 4runner. I've tried loading the threads up with red rtv and crush washer, but it still leaks like mad. Now I'm faced with buying a rebuilt transmission for about $2K. An expensive mistake I hope no one else makes.

 

That nice chamfer on that opening is begging for an 'O' ring. What kind of seal, if any, was on the drain plug?

 

Oddly it had no seal when removed and never had a leak with 180K+ miles. I wasn't using a seal when I over tightened it, but have tried multiple types since hoping I could plug up the crack enough with no luck. The best result was a flat copper washer and some generous red rtv on the threads and it slowed the leak quite a bit, but still got a few drops overnight.

 

I was thinking that obtaining an 'O' ring from a tractor supply store or similar retailer might give you some relief while you can obtain that replacement transmission.

Another avenue to explore might be using an oversize helicoil or another type of thread repair. Such as a "twinsert" or something along those lines. Once a repair is chosen then you could take your original drain plug to a machinist with details of the thread dimensions so that an oversize plug could be made. These alternatives should be far less expensive than a transmission replacement and could be accomplished with the transmission still installed. These types of thread repairs are accomplished on aircraft turbine engines, so it is a possibility for you.

 

On the flip side, since it might be difficult to find a replacement transmission, I would not discard the transmission you have since that case could possibly be weld repaired and new threads could be cut after the weld. Transmission would have to be assembled and cleaned thoroughly for the weld to be performed, but a machine shop could accurately cut new threads and as long as the drain plug is not damaged, it could be reused. I have personally seen these types of repairs performed on gearboxes. It just depends on how near and dear the truck is to you.

 

Clean thoroughly use "https://www.smooth-on.com/products/metalset-a4/" that can be tapped. Used in the inserts for medical helicopter completions to hold litters & passed FAA structure load testing.

 

This is an interesting idea and could solve the problem. I have no experience with this epoxy adhesive, but I have used others that have structural strength.

Edit: Obviously this might be the most cost effective repair assuming that it works. Even if it doesn't, it would not prevent other types of repair.

 

The solutions discussed above may help in the near term. I wonder how likely that crack is to propagate. Maybe not very likely, but it's something to keep an eye on.

 

Can that crack be cleaned and welded? I think that your attempts may be failing because the bolt always re-widens the crack whenever you tighten it even a little. So maybe creating a new drain hole would work.

My thought is this: clean and weld that crack so that it’s positively sealed. Then weld a round plate over the entire opening, and drill/tap a new smaller hole into that plate. It’s a drain after all, so as long as the fluid will come out, you’re ok. You can use whatever bolt/washer system you prefer at that point. Based on what you see in person, might this work?

 

Is the drain bolt on the pan? Is the pan not replaceable?

Sealant shouldn't touch oil while curing. Drain the oil and douse the area with brake cleaner before using sealant. Refill the oil only after sealant has cured. Same story with JB Weld or any other metal epoxy.

You can even install a Fumoto valve "permanently" with a metal epoxy and just use that to drain in the future.

 

I got so wound up with thinking about how to fix those threads that I didn't even think about it being a pan!

 

I could be wrong BUT most all manual transmissions I have ever dealt with do not have a pan, the drain plug is in the transmission housing.

 

^Interesting. The ones from the past 20 years (A340, RC62F) had steel pans.

 

Well as I stated "I could be wrong", that being said again, I believe the A340 is an automatic transmission, which would have a pan on the bottom with a drain plug.

 

I used "teflon tape" on my oil drain plug. Seemed to work great. Now I have a coated washer. Just checked the trans drain bolt. I forgot to use a coated washer and i had a drip on the bolt head. Ofcourse you need a crush or coated washer!

 

Torque spec for auto is 20#'s.

 

Uses a 'crush' washer

Part even has a factory part number

Same for the differentials

 

$12 12157-10010 Toyota Oil Drain Plug Crushable Steel Gaskets Set of 10 OEM 12157-10010

12157-10010 (Gasket, Drain Plug)? That's what my differential fill plug crush washers were.

 

Here's the automatic drain plug crush washer.

 

As @SR5 Limited posted above, it's similar yes

Not sure why people take on specific jobs without knowing what it all entails

 

I gotta swap out two more quarts.

 

Don't want to use steel crush washer on aluminum casing. There's another P/N for aluminum washers like the type used on transfer case plugs. A bit of Googling shows the older manuals had this kind of weird design without a separate pan:

 

Pretty sure those diff crush washers aren't steel. Amazon sellers are idiots.

 

They're not steel

That's what happens when you have a 5th Genner trying to inform 3rd Genners about their vehicles

 

Hey now, I have a 3rd gen, just not a 3rd gen 4R

 

That's how some people learn.

What's the saying? "Good judgement comes from experience, and experience comes from bad judgement."

 

How hot does the transmission get? Would something like solder work? I assume you could clean the threads with a tap pretty easily after that.

For anything filling the crack, I'd worry about complete penetration, but I can picture silver solder or something working if you can thoroughly heat soak the area.

If you want to go full hillbilly fix on it, I'd also consider a rubber wrap outside of the bolt with a hose clamp (either diy or store bought Fernco fitting style).