Stripped Transmission Drain Plug

[Hacker]

This weekend I did a full ATF changeover. Everything was working fine, but tonight I got underneath to make sure everything looked okay. I found a wet area around the drain plug, indicating it was leaking a little.

I tried to tighten it, and ended up overtightening and stripping out the threads on the plug. Unfortunately, the plug is now "stuck" in the drain hole -- I cannot unscrew it because the threads are stripped. The bolt rotates freely, and a little fluid is leaking out from it, but it just isn't coming out. I also can't just grab on to the plug and yank it or pry it out. Again, it is not in tight enough to hold the fluid in...it is dripping out slowly...so I can't just leave it as is and keep driving it.

So, a couple of questions for the more experienced than I under their 4Runners:

- How bad do you guys think the damage here is? It seems like the bolt/plug itself is an alloy (and thus less strong than the steel threads of the pan), so my hunch is that the bolt threads are stripped and the threads on the pan itself are still okay. Obviously if the bolt is stripped and the pan is okay, this is an easy fix...if they're both buggered up, then it is a much more intensive fix involving a new pan, gasket, etc.

- Any suggestions on how to get this bolt out? I've done everything I can think of that won't damage the pan itself: Normal socket, crow-foot wrench, pulling with vice grips, gentle prying under the bolt. My next plan would be to drill-and tap into the bolt and try to pull it like I'd pull a stuck bullet case out of a resizing die.

- If I have jacked the threads on the pan, what's the best place to get a replacement? Buy new, or go to a wrecking yard and get one there?

Here's a shot of the damage. The bolt was not all buggered up when I initially overtightened it -- that's all stuff I've done to it with wrenches and pliers and vice grips trying to get it outta there ever since messing it up.

 

[opie74]

If it were me, Id drop the pan. Get the old bolt and and re-tap the hole for a new bolt. Its likely you stripped the threads in the pan rather than the bolt. So youll have to go up 1 size and get a new bolt. Should be cheaper than a new pan.

If you use a clean bucket, you can re-use the ATF that comes out of the tranny.

 

[Hacker]

Its likely you stripped the threads in the pan rather than the bolt.

Why is that?

I really don't know either way, but I'd think that if it were the pan threads that were stripped, the bolt would come right out rather than what it is doing.

A magnet sticks to both the pan and the bolt, so there is some kind of ferrous content in both of 'em....

 

[gannonrt]

Wow. That sucks. I don't have any advice for you but I always feel better when all around me acknowledge how much something sucks. Hope it helps you feel better since it sure won't help you get that bolt out.

 

[Hacker]

Wow. That sucks. I don't have any advice for you but I always feel better when all around me acknowledge how much something sucks. Hope it helps you feel better since it sure won't help you get that bolt out.

Haha, thanks. I'm smacking myself in the forehead for being such an idiot and causing the problem in the first place. Wish I could blame someone else....but it is just me!

I'm thinking I'll drill a small hole up through the center of the bolt to drain the pan (sllooooooowwwwly), and then either drop the pan or try and get the bolt out by tapping it for a screw to give me some leverage.

If the pan threads are toast, I'll do what @opie74 suggested, and just tap it for a larger bolt.

 

[Crashnrondo]

Did you try to pull down on the bolt while trying to turn it out? You might catch just enough threads to get it started.

 

[Stick Figure]

I had a kid at work do a drain and refill for me before a trip, and later found that he probably over did it on the tightening torque. The bolt actually took the majority of the abuse, but the pan threads weren't perfect. I ran a tap through it to clean up the threads and threw a new bolt in m10x1.25 IIRC and mine has been leak free since.

You may have to pull the pan and give the bolt a tap or pressure from the inside as you turn to get it out. I don't remember if there is enough meat there to move up to the next metric size bolt or not, but you could always use a time sert or one of those repair drain plugs that the auto parts stores sell. Never tried one to say how good or bad they work though.

 

[t4r4life]

it's always the pan that's stripped, get a pry bar or a flat head screw driver, try to get in between the bolt and the pan while un screwing it with a rachet, hopefully the dowward pressure from the prying will help the bolt catch a thread and it would come out other wise you have to drop the pan.

 

[Hacker]

get a pry bar or a flat head screw driver, try to get in between the bolt and the pan while un screwing it with a rachet, hopefully the dowward pressure from the prying will help the bolt catch a thread and it would come out

Yep, that's pretty much what I was doing yesterday before posting....no love on that at all, unfortunately.

 

[Hacker]

Finally got the plug bolt out...and both sets of threads are toast.

So, it is time to replace both the pan and the plug.

Reading back through other posts on dropping the pan, it looks like opinions are divided on replacing the filter vs just cleaning it. I'll have to see what the gaskets and magnets look like when I drop this one to decide what I'm gonna do.

Either way, I'm indebted to the many posts on this forum that have helped me significantly more than any shop manual has! Thanks!

 

[JWaldz]

Why would it not just be easier to rethread it with a die and just use a bigger bolt? Do those plugs have crush sleeves on them as well? It looks like it has a little room for a bigger bolt.

 

[Hacker]

On a whim, I went to an auto parts store and purchased a 10mm x 1.50 tap, and a bolt of the same size/pitch. I wasn't sure that was the size, but a little trial-and-error with the stripped plug showed that was at least close. The bolt I ended up with isn't a flange bolt like the OEM part, and has a 17mm head vs a 14mm head on the OEM.

I ran the tap up into the drain hole in the pan. Although some of the threading in the pan was toast, about 3/4 of it was still good after running the tap in.

I threaded in the new bolt, and it seems to work like a champ. No signs of any leaks or other issues yet. It is a temporary fix, at least.

As mentioned, eventually I want to drop the pan, check/clean the magnets and filter, and probably replace the pan and plug with OEM.

Thanks again for the help, guys!

 

[opie74]

Just get yourself a flat washer and a rubber washer and call it done.

 

[Dous]

Yea most definitely get a crush washer, you can buy a pack of misc sizes at a parts house for a good price

 

[ycl1688]

Here is the part # you need to get the new pan, if needed.
The Transmission Pan (35106-35110) around $87.75 online.
Toyota recommends using Sealant (00295-00103) which is $10.37, instead of a Gasket.

 

[opie74]

Yeah, save yourself the headache and get a gasket. I haven't had a drop leak out of mine.

 

[Hacker]

Yea most definitely get a crush washer, you can buy a pack of misc sizes at a parts house for a good price

Cool, thanks. Overnight it leaked just the slightest bit out around the replacement plug, so I'll be buying exactly what you recommend today.

 

[Android_02]

I did this EXACT same thing as you, over-tightened the drain bolt and had a slow leak. Tried to pry it out by turning the bolt and getting a flat head screwdriver in between the pan and bolt and still had no luck. I finally got it out by pulling as hard as i could...it was like pulling out a tooth. The threads in my pan were just a little messed up and I just chased the threads using the m10 x 1.5 tap then bought a new plug and gasket from the toyota delaership and it screwed in tight. Have had it that way for 4 months now without any leak what so-ever!! Glad someone else made the same mistake as me. It was an awful feeling just having that drain plug just spin without tightening or loosening with a tiny leak and I tried everything to get that little bugger out. Glad it worked out for us, I don't think you'll need a new pan....it's kind of a pain to drop because of that FIPG(formed in place gasket) on there.

 

[Android_02]

Oh and one more thing the torque spec for the auto trans drain plug is 15 ft/lbf. Definitely something to know before hand since that plug strips EXTREMELY easy. And you were right on with the oem bolt...its a m10x1.50 with a 14mm head. I read a few threads where a guy tapped up to the bigger bolt but in SAE size which is the 7/16-14. You could also do that if you had a little leak, just tap the hole with a bigger bolt. Here's the thread it seemed to work for him.
RE-TAPPING a 3.4L TRANSMISSION PAN DRAIN PLUG - YotaTech Forums

 

[Hacker]

Thanks for the link to the YotaTech thread. Wish I'd seen it last month, because my situation pretty much turned out the same as his!

Glad you were able to solve yours the same way.

For future victims of this, the good news is that the trend seems to be that the bolt is the first to strip, leaving the pan threads in good enough shape to be re-used after cleanup with a tap. Much less expensive and much less pain that way.