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A Front Diff Drain Plug that Doesn't Suck

Anyone who owns a 4WD Toyota and has dealt with the drain and fill plugs on the IFS front diff knows that they generally suck. They use either a 10mm or 12mm hex key, and that can be a problem for many reasons:

  1. The recess that the key fits into can easily get filled up with crud.
  2. If the recess isn't cleaned and the hex key doesn't fully seat, it's easy to round over.
  3. Hex key's aren't generally all that long, so it's hard to get the leverage needed to loosen the plugs.
  4. The plugs can get extremely tight, making it hard to loosen with a hex key.

There are ways around some of these shortcomings of course - you can fully clean out the recess, you can use a hammer to rap on the drain plug a few times before removing it, and you can try using a hex impact socket. But in all those cases, we're really just working around something that could be better anyway.

I don't know why Toyota did this to us all, but some number of years ago, they realized how terrible it was. And so they made new plugs that had traditional 14mm hex bolt heads. All was going to be right in the world, once again. Except that they decided they'd limit these new plugs to Lexus vehicles, continuing to install the hex key-style on Toyotas.

Luckily for us Toyota owners, the Lexus plugs fit our differentials as well. And today, I'm making my life just a little less painful by switching out the drain plug for the front diff - since I'm changing the oil anyway. The process is easy.

  1. Loosen the fill plug at the top-front of the front diff. Always loosen the fill plug first, to make sure you'll be able to refill the diff after you drain it.
  2. Loosen and remove the drain plug at the left (driver)-side-bottom of the front diff. Drain the oil into a catch can.
  3. Throw the horrible drain plug in some bin somewhere.
  4. Replace the crush washers on both the fill and drain plugs with with new crush washers.
  5. Replace the drain plug with the Lexus OEM version (90341-24016).
  6. Refill the diff with some new diff oil (I like Lucas 80W-90). Buy it by the gallon to save a few bucks.
  7. Reinstall the fill plug.

That's it. Your future self will thank you.

8 Comments

  1. Jim Roegiers
    Jim Roegiers July 21, 2020

    If both plugs are a bad design, ?why not replace both with the Lexus plug?

    • turbodb
      turbodb July 23, 2020

      It's a great question Jim! I would absolutely replace both plugs, but I don't know the replacement part number for a front diff fill plug with a hex head instead of Allen key.

      If you find out what it is, I'd love for you to post here and let me know!

  2. Jim Roegiers
    Jim Roegiers July 23, 2020

    Thank you turbodb.

    I will investigate and if successful, I will let you know. Seems as if the drain plug gives everyone the problem. Not the fill. But would love to replace both. I really appreciate your reply here. Thank you.

  3. Cyrus
    Cyrus September 3, 2020

    The problem here is the torque required on the drain plug (48 ft-lbs). The fill plug requires less than 30 ft-lbs so is much easier to take off.

    • turbodb
      turbodb September 3, 2020

      I'm not sure exactly what you mean by "the problem here," Cyrus - would you mind expanding on that? Thanks! 👍

      I think that what a lot of folks run into is the fact that the heat/cool cycles of the diff cause the plugs to tighten beyond the torque specs. That, and these plugs are often reinstalled to tightness's beyond the torque spec.

      I've always found that a good tap on the plug prior to loosening can help with that, and of course, making sure to clean it out prior to inserting a hex key -- but not everyone is in a situation where the plug is still in good enough shape for that to work.

  4. Cyrus
    Cyrus September 3, 2020

    I haven’t had issues before after changing my front diff fluid about 4 times now but tonight I was trying to loosen my fill plug and I managed to round out the female hex. Above, Jim has mentioned that the drain gives people a problem. It does because the 10 mm hex doesn’t provide enough torque to get the bolt out and then it gets rounded out. I’m going to try Lexus tomorrow morning to get the 14 mm socket drain plug. Next time I’ll tap the plug with something to loosen it up but the 14 mm should provide my force to loosen the drain in the future.

    • turbodb
      turbodb September 3, 2020

      Ahh, gotcha! Yeah, I agree with ya 💯. If you haven't gotten the fill plug out yet, you might try the tapping trick, and then make sure the hex key is as well seated as it can be.

      Once you get it out, take it to Lexus and see if they have a hex head replacement for it as well - we all want to know! 🙂

      Good luck!

  5. Cyrus
    Cyrus September 9, 2020

    I was able to get it out. I went to Lexus and they didn’t have it in stock. I purchased another hex from Toyota because they had it in stock. I have the 14 mm ordered though Lexus so the next time I take out the hex bolt I’ll put the new one in. Thanks!!!

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