Bolt ID Question

[ZVKep]

Hi Folks,

This is on a 1986 Tercel Wagon 2WD, 3AC, automatic.
I am looking at a common-head bolt (apparently) just below the fill plug on the transaxle, and it has a leather gasket. Not sure if it is leaking or not, but there is less grime buildup around it than the surrounding areas. It's giving out-of-place vibes. See attached a picture.

IMG-6196.jpg

I can't find this thing in my manual or searches. Before I take it out to see, can anyone share what this is?

Many thanks! --Zach

[Mark]

The differential filling plug looks like it's been rounded off. That flat-head screw looking thing under it might have been drilled to make a hole to fill the differential after they drained it without making sure they could take the fill plug out first. I can picture them swearing as they tried to take that fill plug out, using various combinations of wrenches, sockets, hammers, pipe extensions, while the hex head gradually rounded off. I know this from personal experience.

[ZVKep]

Yikes. I see it now. Many thanks for the quick insight. --Zach

[Paul]

Hi Zack... Maybe these bolt extractors would grab it
https://www.lowes.com/pd/IRWIN-BOLT-GRI ... 1003021030
I used them successfully on some stripped allen head bolts. I agree with Mark's assessment. If they sweared over the bolt, it's probably cursed... I would pray over it and try the extractor. Selecting one that fits tight and tapping it on with a hammer allows the teeth to bite.
If you're stuck with the add-on screw, looks like fill to overflowing plus a little more, referring to page AT-29 of the FSM.

[Mark]

So this has happened to me before and today it happened again. I was replacing the torn CV axle boots on my drive axles on my '81 Tercel and I decided to change the gear oil in the differential. I tried to take the filling plug out using a pipe extension on my socket wrench and a hammer, but as usual, it wouldn't come loose. I decided to try using an impact socket wrench. As soon as I pulled the trigger, it completely rounded off the hex head of the plug. I guess it had too much torque and the steel was too soft. So now that fill plug is in there pretty much permanently too. I was still able to fill the differential through the drive shaft hole since one of the CV axles was out. This seems to happen to me on every Tercel I've had. The dissimilar metals (aluminum differential casing and whatever kind of steel they use for the plug) really seize up together. I wonder if in the future, antiseize would work on the threads.

[dlb]

So this has happened to me before and today it happened again. I was replacing the torn CV axle boots on my drive axles on my '81 Tercel and I decided to change the gear oil in the differential. I tried to take the filling plug out using a pipe extension on my socket wrench and a hammer, but as usual, it wouldn't come loose. I decided to try using an impact socket wrench. As soon as I pulled the trigger, it completely rounded off the hex head of the plug. I guess it had too much torque and the steel was too soft. So now that fill plug is in there pretty much permanently too. I was still able to fill the differential through the drive shaft hole since one of the CV axles was out. This seems to happen to me on every Tercel I've had. The dissimilar metals (aluminum differential casing and whatever kind of steel they use for the plug) really seize up together. I wonder if in the future, antiseize would work on the threads.

I have never had this happen. I use the same technique as you, using a 24 mm socket on a large ratchet with a pipe extension. Occasionally if the bolt head appears worn I have used two wrenches, like in this video:

https://youtu.be/SDI4j1LgqV4?t=56

Anyway, sorry to hear it Mark. That's obviously a very frustrating PIA.

[Mark]

On mine the drain plug is a 24mm and I've never had a problem with them. The fill plugs are 17mm on the 1st gen. I don't remember what the fill plug size on my wagon is. I feel like the smaller size is more prone to rounding off.

[rer233]

Years ago, I bought a six-point (rather than the more common 12 point) socket just for this job. No problems since.

[dlb]

Years ago, I bought a six-point (rather than the more common 12 point) socket just for this job. No problems since.

I think it was Tom here who ground his 6-point socket down so there was no chamfer on it, just because the fill plugs are so short. I've never needed to go that far but I've always remembered it.

I looked it up and yup it was Tom: viewtopic.php?p=51837&hilit=chamfer#p51837

[Mark]

Years ago, I bought a six-point (rather than the more common 12 point) socket just for this job. No problems since.

Oh, I definitely only use a 6-point socket on these things. When this happened on my '84 wagon years ago, I tried everything from a torch to a chisel to try and get the rounded-off plug out. Eventually, I removed the trans (when I had to do some internal work for other reasons), separated the diff and brought it into a shop to see what they could do with it. I think they ended up drilling it out.

[Mark]

Years ago, I bought a six-point (rather than the more common 12 point) socket just for this job. No problems since.

I think it was Tom here who ground his 6-point socket down so there was no chamfer on it, just because the fill plugs are so short. I've never needed to go that far but I've always remembered it.

I looked it up and yup it was Tom: viewtopic.php?p=51837&hilit=chamfer#p51837

Grinding down the socket is a good idea too. I've found that the 15mm socket feels kind of loose on these plugs, even when the plug is new. The standard equivalent is even looser. The hex head on the plugs seems slightly undersized, which is a head start to rounding-off.

[NWMO]

I’ve fought these some, but not too bad. I keep the stock “thin” drain plugs on the bottom, my 15/16” socket has always removed them with a breaker bar and a little care. About any side fill plug I remove gets swapped with a new 19mm plug with a nice tall top. O’Reilly AP carries them and they sure are nicer to remove.

Chris