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Rust on rear diff

Discussion in '2.5 Gen Tundras (2014-2021)' started by Texan_Tundra21, Feb 22, 2021.

  1. Feb 22, 2021 at 6:04 PM
    #1
    Texan_Tundra21

    Texan_Tundra21 [OP] New Member

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    What’s up everyone, I looked around on here before posting but couldn’t find anything answering this specific question. My 21 rear diff is starting to show rust on the welding seams which sux but I wanted to see what guys are using to combat the progression of rust and or using to repair rusting that has already taken place. Thanks in advance.
     
  2. Feb 22, 2021 at 11:05 PM
    #2
    panicman

    panicman Everyone remain calm.

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    If needed, a product like fluid film. Clean first, then apply.
     
  3. Feb 23, 2021 at 12:54 AM
    #3
    RPO 579C

    RPO 579C New Member

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    I use CRC Marine Corrosion Inhibitor. Very effective against our over-salted Minnesota roads.
     
  4. Feb 23, 2021 at 1:26 AM
    #4
    preacher35

    preacher35 RIGHTEOUS MEMBER

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    Damn! That is rather quick, for a 2021 already forming rust.
     
  5. Feb 23, 2021 at 2:26 AM
    #5
    Northbound Train

    Northbound Train Masshole

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    I bought my 2016 used in 2018 with 32K miles. It had rust starting on welds in various places on the frame. Knowing I was going to be driving it in the winter in the Northeast and intending to keep it for a long time, I painted the welds with chassis saver ( a paint like POR15 but I like it better) and then painted the whole frame with Rustoleum. I'm not going to say it wasn't a pain in the ass. Then every year I have the underside sprayed with NH oil which is similar to fluid film. There is not a speck of rust returning or starting anywhere and I don't expect it will for years.
     
  6. Feb 23, 2021 at 3:53 AM
    #6
    Barrett50

    Barrett50 New Member

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    I 2nd CRC, seems to stick waaayyyyy better than FFilm.
     
    panicman likes this.
  7. Dec 10, 2021 at 6:00 AM
    #7
    MeetJoe

    MeetJoe New Member

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    Details on CRC Marine application please! I have a 2021 with 16k and no previous undercarriage treatment. It held up okay through last winter but want to be proactive while I can.

    Is it as simple as: 1) clean the truck. 2) let it dry. 3) spray anything /everything metal? What do you avoid? What shouldn’t you spray?
    I’ve done research and want to go with a marine CRC but want to make sure I don’t spray something I shouldn’t. Any details would be great.

    what if there is surface rust? Spray over it? Or use a rust-reformer to “kill it” then spray CRV over top?

    can I spray leaf springs?

    How about rust on the rear diff? Spray it?

    bolts?

    image.jpg
    image.jpg
    image.jpg
     
    Last edited: Dec 10, 2021
  8. Dec 10, 2021 at 6:50 AM
    #8
    Spyker

    Spyker I’m a dude,playin a dude,disguised as another dude

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    check this thread out, a lot of great info:

    https://www.tundras.com/threads/undercarriage-treatment-yay-or-nay-pros-cons.99051/
     
  9. Dec 10, 2021 at 7:14 AM
    #9
    MeetJoe

    MeetJoe New Member

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    That is where I started which is how I decided on CRC Marine. I have surface rust. Does anyone know if I need to prep that, or can I spray this on it?

    Do I hit it with a wire brush, then rust-reformer, and then CRC Marine? or will CRC Marine do the trick by itself? It is not flaking or bubbling yet. Just surface.
     
  10. Dec 10, 2021 at 7:19 AM
    #10
    BecauseRacecar

    BecauseRacecar New Member

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    I've been using fluid film for 5+ years across several vehicles and won't use anything else. My tundra looks like your pics now after 2 winters in the rust belt, which I'd call a win.

    In terms of prep, generally you want to avoid painting over rust. I don't know how the CRC product works, if it will seal in existing rust or if it has any "reformer" qualities to it. If it does do any sealing, you'll want 120 grit sandpaper or a wire wheel to really buff it down to bare metal before doing any touch ups.
     
  11. Dec 10, 2021 at 8:56 AM
    #11
    Northbound Train

    Northbound Train Masshole

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    You don’t want to spray any rubber parts.
     
  12. Dec 10, 2021 at 11:00 AM
    #12
    RPO 579C

    RPO 579C New Member

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    Especially since the CRC isn't cheap.

    I sprayed everything that could see any bit of rust on after power washing the underside of the truck and letting it dry for a few days. No brushing needed in my opinion. That was in the fall of 2020, and my intention was to do a touch up in the summer of '21 but there was none needed. Some parts that will eventually need the come apart, like the threaded tops of the shocks will be somewhat resistant with the CRC on them, but they would be much worse with thick rust.

    Just wear a breathing mask and eye protection. And rubber gloves. As the instructions say, use in a well-ventilated area.

    CRC is extremely tough stuff.
     
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  13. Dec 10, 2021 at 11:18 AM
    #13
    Barrett50

    Barrett50 New Member

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    I use this on any surface rust. Apply 2-3 times, turns metal black and then the CRC or Amsoil MPHD
    Permatex Rust Treatment (10 oz) Bundle with Latex Gloves (6 Items) https://www.amazon.com/dp/B01MTOKOER?_encoding=UTF8
     
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  14. Dec 10, 2021 at 10:51 PM
    #14
    panicman

    panicman Everyone remain calm.

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    I have used the Permatex rust treatment.

    I used it in several places on my 1960 VW beetle.
    Areas that had rusted through were cut out and replaced with new steel. Areas that had suffered deep, but non-penetrating rust were sanded to shiny, pitted metal. Those areas were treated with the Permatex. Over many areas, I then applied a skim coat of body glaze. After all areas were treated, the body was given a final sand, then cleaned with solvents, then primed and painted. That was 11 years ago. The risk with any of these products is failure over time, or incompatibility over time. The Permatex has done well. As promised, the use of this rust converter essentially creates a compatible medium for primer or paint. After use, the application area turns black, almost like primer black, and you can sand it smooth and prime and paint it like metal. I have seen no evidence of failure-
    No blistering, flaking, anything. It’s a good product, sold through Napa.

    420A6032-18E3-47DD-89A4-71239586E44C.jpg
     
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  15. Dec 11, 2021 at 4:37 AM
    #15
    MeetJoe

    MeetJoe New Member

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    Thanks for the details. Any harm spraying the mounting disk on the rear diff/drive train joint in the photo above? Obviously not the knuckle. Nothing that makes contact with an other part, nothing that gets hot, etc.

    What about the bolts around the rear diff?

    A painted bolt (although rustoleum rust reformer is not really paint) is tough to loosen up, but it’s better/easier than rust?
     
  16. Dec 11, 2021 at 11:35 AM
    #16
    Barrett50

    Barrett50 New Member

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    I’ve sprayed my mounting disk and all the bolts that had surface rust and even the joints on the exhaust. Fortunately and unfortunately the permatex doesn’t come out of the can very heavy so you can be pretty precise with it. Same with the CRC. The mphd flies out and is WAY better at getting in hard to reach places. I highly recommend getting your hands on some.
    I also filled the doors and rockers with 3M cavity wax. It’s a little pricey but you should really only have to do it every 3-5 years I would think. I’ll probably do the rockers sooner, next time I take the sliders off to touch up and rust proof underneath where they mount.
    I’m no expert but it’s worked good for me so far.
     
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  17. Dec 11, 2021 at 2:10 PM
    #17
    normagene

    normagene New Member

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    I had a bit of rust on my ol tundra.

    4D9A9392-D6B9-424B-B9AC-9D6EE49ADAF0.jpg
     

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