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  1. #1

    Default Transmission Pan Drain Plug Kit

    91 Suburban 5.7 4L80E

    Soon I'll be changing the tranny filter out and replacing only the fluid lost from the pan. No intentions of a flush, the fluid looks and smells good, and the tranny is working fine, just a preventative maintenance measure. However, the pan doesn't have a drain plug and I'd like to install an aftermarket plug kit.
    Where should I drill the hole? It looks like there is a slanted area that would be perfect for a plug, but would it be better to go straight through the bottom?
    Theres a circle on the bottom of the pan that holds the magnet, so I'll stay away from that.
    Small issue, but wondered what other people thought or their experience.

    Click image for larger version. 

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    91 Suburban R2500

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  2. #2
    murdog94's Avatar
    Join Date
    Feb 2008
    Cloquet, Minnesota, United States
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    If that slant is what i am seeing in the middle of the pan i would try to get it to fit there, that way there is a bit of a cup that will help the old fluid come out.


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  3. #3
    Master Mechanic clgoch187's Avatar
    Join Date
    Aug 2010
    Gettysburg, Pennsylvania, United States


    i wouldn't worry about,its not that hard to let the pan tilt to drain and how often do you plan on draining it? and you gotta drop the pan to change out the filter anyways right?

    i just did the tranny filter on my 03 and its got a stock drain plug that cant be used..... i mean i cranked on it, lubed it, even heated it a bit and nothing. iw as scared that any more torque on it would twist the pan, and we've run into the issue time and time again with the newer gm's and the shop i work at.
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  4. #4


    The first thing, is are you sure you have a 4L80E? I would think you probably have a 700R4, which probably wouldn't have a drain plug either. In the even you do have a 4L80E, you can go to the junkyard and pick up a pan off a 1-ton truck that has a 4L80E. A lot of them have drain plugs dead center of the pan, with a T-60 head. I know my uncle's 99 1-ton dually has it. That would probably be cheaper and easier than installing a bung on your existing pan and installing a drain plug.

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  5. #5


    I'm pretty sure its a 4L80E, based on searches on the online autoparts stores its the only tranny available for my truck, it does have the enormous wiring harness attached to it, and the 17 bolt pan. Also this website has some info:

    The slant in the middle of the pan seems like it may have been put there on purpose, so I might head that direction if I can't source a cheap/easily removed later model pan.
    I'll be changing out the filter every 2 years barring a failure. And when it comes to the tilt method, for me, historically has turned out messier than I would like.
    I was thinking I could drill a hole(carefully using a stop on the drill) to drain the fluid initially, then change out the filter and install the drainplug kit while the pan was off, then reassemble.
    This is a type of kit I was considering, no welding required.

  6. #6


    B&M makes a drain pan plug kit. Had one in my '96 suburban before I went to a deep aluminum pan with plug.

  7. #7


    I tried around town to source a pan from salvage yards and a couple tranny shops, but nobody had one and to confirm clgoch187 several of the places stated they had problems getting the bolts loose as well. I was able to pick up a Mr. Gasket tranny drain plug kit from the local hotrod shop for 9$. I'll probably be putting it in the slant towards the middle of the pan, but the truck is having bigger issues right now(covered in another thread) so I might not get around to it for a little bit.
    Thanks for the input and I'll update how it goes!

  8. #8

    Default Drain Plug Location

    I know this isn't the most elaborate or exciting thing posted to the forum, but this is what I ended up doing. Seems to work well with no observed leaks. We'll see how it goes after a few heat cycles. As a side note some of the pan bolts were ridiculously tight, had to use extra PB Blaster, some tapping with a hammer, and even the (scary move)impact to get a few out. The fluid looked clear and red, smelled good. There was a little bit of goop in the pan, but no big chunks. Hopefully with proper care and smart driving theres thousands of miles left on it.
    Tip: Make sure to drill a pilot hole first, then work up to the larger bit. Also remove any burrs in the hole with a round file or flapwheel or both.
    Click image for larger version. 

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  9. #9


    A quick update, it leaks. Just a little drop, but I don't like it.(Just a standard NPT plug in a bulkhead fitting-Should have know better, I deal with all kinds of fittings at work and NPT are the most prone for leakage). I'll have to pull the pan to tighten the bulkhead fitting, so I figured I'll tack it in place while its in there. I despise rework, especially when it is my own mistake, so I'll have to get deep into this one to get it right. But. I just moved in with misses and no 220V in the garage for the welder, and we might be moving soon anyways, so may not get around to it for a bit. Maybe, I'll just look harder for a pan with a plug already in it.

  10. #10

    Join Date
    Sep 2010
    everett, massachusetts


    this drain plug was installed with permenent lock tight. the pan will require removal then heat the drain plug until it glows [use goggles] then using a 6pt socket 1/2inch drive slowly increase torque till the plug breaks free. my plug blew out the lock tight like a mini explosion..

    having this drain plug helps remove the fluid to make this an easier job. or even to help lower fluid level,,,,.

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