Transmission drain plug woes

JHZR2

Staff member
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
This is on a 96 LandCruiser a343 automatic transmission. Dropped the pan and replaced the filter last week. Wanted to do a drain and fill this week. Removed the m10x1.5 drain plug via 14mm bolt head. All seemed fine. Drained out about 6qts. Cleaned it and went to reinstall the plug with a new crush washer. It didn’t want to overtorque it, but the bolt wasn’t cinching down as I tightened it with my torque wrench. I went to loosen it and no dice. It just spun.

I tried a number of things, but eventually had to drill it out partway, which let us remove the plug.

C35E62EF-092B-45B1-91CF-72714F5AE9E1.jpeg
2E5A0A07-21B2-475F-8089-323845531E42.jpeg


Went to parts stores and it’s hard to know if an m12 will fit. I found m10x1.5 flanged bolt (same as the plug) that wouldn’t go through the drain hole. A 7/16-14 would have been better but searching for this on a Saturday pm was becoming g a wild goose chase.

I tapped the hole for m10x1.5, which was the OE plug. I used a new flange bolt and it has held. I torqued carefully up to 12 ft-lb without issue.

C2CDD776-B4D6-4F2F-8833-A4A4C555E944.jpeg




6FC3362C-E91E-4EB2-8A85-75C43D17E0CA.jpeg


So far so good. It torqued to 12 ft lb which is enough to crush the washer. Wasn’t going to get a time sert or anything on Saturday night. I’m not sure there’s enough meat to do a time sert anyway.

It isn’t loosening or leaking. Should I be concerned?

I’m concerned that drilling out further will be detrimental.

Any thoughts how durable the current setup might be?

There isn’t much that can be done…

D3B84051-FD64-410C-A7B8-86DFE1CA7236.jpeg
 
Last edited:
Joined
Jul 13, 2003
Messages
2,592
Location
Tracy, CA
Is replacing the pan an option?

I would ditch the crush washer and use either a fiber/plastic washer or better yet, a Stat-O-Seal washer (if the area around the plug will accommodate one). You wouldn't have to tighten it as much to get a seal and risk stripping whatever chased threads are still there.

 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
Is replacing the pan an option?

I would ditch the crush washer and use either a fiber/plastic washer or better yet, a Stat-O-Seal washer (if the area around the plug will accommodate one). You wouldn't have to tighten it as much to get a seal and risk stripping whatever chased threads are still there.

Replacing the pan is possibly the best option. But it doesn’t get the truck back on the road. I’m surprised at how little aftermarket support there is for this transmission, considering how much there is for LandCruisers overall.

It seems to be a pervasive issue with these pans. Steel pan with a softer metal internal section that tends to strip.

I did wonder why OE is a crush washer (that frankly doesn’t fit well or center well on the OE drain plug), vs a better fitting soft copper or aluminum washer. The differentials and transfer case use an aluminum one, the oil pan uses fiber.

I will look into easier/better sealing washers. I have to wonder if I should try to drill and tap a 7/16-14 thread??/
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
It should be fine. If you are that worried about it falling out put a dab of silicone on the outside.
It hasn’t fallen out or leaked after 80 miles of use. You mean under the bolt head, or just generally around it?
 

D60

Joined
Nov 6, 2017
Messages
1,590
Location
Colo
Replacing the pan is possibly the best option. But it doesn’t get the truck back on the road. I’m surprised at how little aftermarket support there is for this transmission, considering how much there is for LandCruisers overall.

It seems to be a pervasive issue with these pans. Steel pan with a softer metal internal section that tends to strip.

I did wonder why OE is a crush washer (that frankly doesn’t fit well or center well on the OE drain plug), vs a better fitting soft copper or aluminum washer. The differentials and transfer case use an aluminum one, the oil pan uses fiber.

I will look into easier/better sealing washers. I have to wonder if I should try to drill and tap a 7/16-14 thread??/
If it's holding I'd leave well-enough alone.

I couldn't figure out why you're hung up on coarse thread until I realized the factory plug was M10 coarse (probably a significant part of the problem IMO). If you're insistent on fractional, I'd run 7/16-20. That's just me.

Plan C: grab an M10x1.5 castle nut (or have one machined) and turn it upside down in the pan on your new gold bolts shown. Grind off paint inside, tack castle nut where it touches, done. Be sure to do this with the bolt threaded through both or you'll wind up with a sorta offset double lead thread, which won't work :D
 
Joined
Nov 9, 2008
Messages
20,861
Location
NH
How clean was the fluid? wondering if ordering a new pan and swapping in at next change, since it might occur soon, would put the issue to bed.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
How clean was the fluid? wondering if ordering a new pan and swapping in at next change, since it might occur soon, would put the issue to bed.
Fluid was slightly brown at first pan drop. Yet distinguishable as ATF and red.

5ED9BA2F-FA87-44FB-8991-08DFABD3F5BD.jpeg


A 1996 LC sounds like a sweet rig. Does the trans shift pretty good?
Extremely smooth. Only has 176k miles.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
If it's holding I'd leave well-enough alone.

I couldn't figure out why you're hung up on coarse thread until I realized the factory plug was M10 coarse (probably a significant part of the problem IMO). If you're insistent on fractional, I'd run 7/16-20. That's just me.

Plan C: grab an M10x1.5 castle nut (or have one machined) and turn it upside down in the pan on your new gold bolts shown. Grind off paint inside, tack castle nut where it touches, done. Be sure to do this with the bolt threaded through both or you'll wind up with a sorta offset double lead thread, which won't work :D
Yeah the M10 coarse is a big part of the problem…. It’s like two threads for the plug to grab into.

When you say about a castle nut on there, do you mean put it on top of the current little dimple that’s attached to the pan, or grind it off first?

I don’t know much about welding. The pan is thin steel… how would you tack it on? I bought a cheap low power flux welder but my understanding is that you can easily blow through thin metal with it. What should one use to tack it?

Thanks!
 
Joined
May 30, 2010
Messages
15,663
Location
North Carolina
I don’t know much about welding. The pan is thin steel… how would you tack it on? I bought a cheap low power flux welder but my understanding is that you can easily blow through thin metal with it. What should one use to tack it?

Thanks!
Better gas mig welded than flux. You are correct, if its thin it might burn through. You would only need 2 good tacks , one on each side. I'd do four each at 90 degrees. As @D60 stated, clean the paint off, clean all the oil off with NO BRAKE CLEANER( At least not chlorinated). Put the bolt through the pan with the gasket removed( to not melt it) spin the nut down on it lightly snug, and tack weld it.

Is there room to drill and put an M-12 bolt in there? IF so this would work for $25.

 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,499
Location
New Jersey
Better gas mig welded than flux. You are correct, if its thin it might burn through. You would only need 2 good tacks , one on each side. I'd do four each at 90 degrees. As @D60 stated, clean the paint off, clean all the oil off with NO BRAKE CLEANER( At least not chlorinated). Put the bolt through the pan with the gasket removed( to not melt it) spin the nut down on it lightly snug, and tack weld it.

Is there room to drill and put an M-12 bolt in there? IF so this would work for $25.


I don’t have the need or desire to get a mig setup…. Though maybe I should ask Santa for one…

That retrofit plug looks good. There’s plenty of flat surface area. The issue is if I want to drill out the old one. Yesterday I didn’t. For a more permanent solution it maybe ok…
 
Joined
Apr 9, 2008
Messages
15,981
Location
Central NY
I’m surprised at how little aftermarket support there is for this transmission, considering how much there is for LandCruisers overall.

Jeep Cherokees used a variant of that transmission. In fact the bellhousing and pump from the A343 gets used when people will put a Toyota / Lexus V8 into a Jeep. There's no aftermarket because these transmission are pretty much indestructible. Don't need to upgrade what doesn't fail.
 
Top