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Stainless bolt in aluminum?

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  • Stainless bolt in aluminum?

    Thinking about replacing the transmission pan bolts on my truck with stainless steel, tired of the rust.
    Google says that there might be issues, especially in a marine environment, ok, I get that. What about the underside of a truck?

    Thoughts?
    Mike Hunter

    www.mikehunterrestorations.com

  • #2
    I think if you put them in with anti-seize you'll be fine.

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    • #3
      Underside of a truck is worse than marine, it is nearly a "tidewater" environment in some places around here and north.

      Just depends on the city/county salt budget.
      1601

      Keep eye on ball.
      Hashim Khan

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      • #4
        Common practice where I'm at(Gulf Coast) I use teflon pipe dope instead of neversieze.Seals water out and less mess.
        I just need one more tool,just one!

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        • #5
          SS screws are used in aluminum all the time. Even in salt spray areas.

          If you are worried about galvanic corrosion, just spray the heads with undercoat.
          Paul A.

          Make it fit.
          You can't win and there is a penalty for trying!

          Comment


          • #6
            Originally posted by Mike Hunter View Post
            Thinking about replacing the transmission pan bolts on my truck with stainless steel, tired of the rust.
            Google says that there might be issues, especially in a marine environment, ok, I get that. What about the underside of a truck?

            Thoughts?
            Keep in mind stainless bolts are weaker and require lower torque, along with being difficult to find with flanged heads like your OEM bolts probably have. I would not do it.

            What I would do is, if it's a serious problem, is install clean bolts with blue Loctite 243, which will seal the threads from corrosion, and then paint the installed bolt heads with a good epoxy paint. VHT black epoxy paint is available at our local auto parts stores and is a good choice.

            That only addresses those particular bolts though. What about everything else on the truck? And why are you concerned with the transmission pan bolts in particular?

            Comment


            • #7
              I agree with post #4 except use the liquid teflon pipe sealer. The sealer lubricates the threads so there is no chance of the stainless picking up the aluminum and as he says it also seals out the water that contains the salt. I have seen stainless machine screws put in an aluminum mast that way and spent 20 years or more in salt spray and some tropical conditions. You could still crack them loose with a good screwdriver and remove them with your fingers. I always used 300 series stainless fasteners preferably 316, which are very corrosion resistant.
              Larry - west coast of Canada

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              • #8
                Originally posted by Yondering View Post
                Keep in mind stainless bolts are weaker and require lower torque, along with being difficult to find with flanged heads like your OEM bolts probably have. I would not do it.

                What I would do is, if it's a serious problem, is install clean bolts with blue Loctite 243, which will seal the threads from corrosion, and then paint the installed bolt heads with a good epoxy paint. VHT black epoxy paint is available at our local auto parts stores and is a good choice.

                That only addresses those particular bolts though. What about everything else on the truck? And why are you concerned with the transmission pan bolts in particular?
                Disagree completely. Look up ARP fasteners. Chances are they have a kit for the pan/bolt you need. If not I know they have the flange head you seek. Plus, they are high strength compared to anything your likely to find in a hardware store. Come in 6 and 12 point should you desire. I use ARP fasteners most all the time. Also look up totally stainless out of PA. They carry their stuff.

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                • #9
                  I'm at a loss on this whole conversation as I've always used stainless in aluminum due to its lower reactivity. Also you can get various grades of stainless fasteners. I use stainless clamping bolts, stainless alignment pins, stainless hinge pins, stainless handle rods. There is a whole world of stainless hardware available if you don't limit yourself to the Hillman garbage found at your local box store. Often at the local bolt store I can buy a whole box of stainless screws for the price of a mere handful from Blowes or Home Despot.
                  *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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                  • #10
                    Generally stainless steel in aluminum is okay if the aluminum is the big part and stainless is the fastener (aluminum aircraft use stainless rivets frequently). The other way around is a disaster. As suggested make sure you use something on threads. Loctite is a good suggestion - one of the best products for this purpose is Loctite's Vibraseal.
                    www.thecogwheel.net

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                    • #11
                      I have a canoe which has aluminium plates and the handles to the canoe are stainless bolts. The strap handle broke and I could not remove the ss bolts because they somehow glued themselves to the alu plate through electrolsis ,I suspect. This has become a major disaster because the alu plates are fibreglassed into the mold and are not accessible.What metal will not react to alu in a marine environment?

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                      • #12
                        Yeah, stainless in aluminum can gall so use something to prevent that, anti seize or get silver flash plated bolts.

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                        • #13
                          Originally posted by macona View Post
                          Yeah, stainless in aluminum can gall so use something to prevent that, anti seize or get silver flash plated bolts.
                          Problem is usually the white powdery aluminium oxide forming in the joint, like rust but 100x harder!
                          Solution is to seal the thread from enviroment, good anti-seize helps for a while and threadlock/pipe sealer for loooong time.

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                          • #14
                            Perhaps the following link shall provide some information on the principles of choosing compatible materials to prevent risk of galvanic corrosion:

                            https://structx.com/Material_Properties_001.html

                            I would take the compatibility table with a healthy grain of salt though......e.g. it suggests that it is "safe" to use a combination of aluminium and steel, but in my experience that leads to quick corrosion apocalypse. Especially if chlorides are involved.
                            There should be special alloys available that can be used safely in combination with aluminium. For example Audi a8 body is made of aluminium and all the fasteners that are attached to it are made from a special alloy to prevent corrosion. If one unknowingly replaces one of these with a regular steel fastener, the aluminium shall corrode superfast if road salt is involved and all that will be left after one winter season is a hole in that location.

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                            • #15
                              I wouldn't think twice about it. Fire some stainless in there and forget about it.

                              All outboard motors (fresh and salt water models) are held together with stainless fasteners. Likewise with aluminum boats.



                              But I must ask. Are you doing this for just looks? Or did your stock bolts rot away? I ask because I have never ever ran into a trans pan bolt rotting away tot he point where a leak started or the pan fell off. Also for changing trans fluid/filter/maintenance really only needs to be done once in a vehicles lifetime. If you get close to a million miles out of your truck you might have to change the trans fluid twice possibly three times if your towing.

                              Don't over think it and if you are just trying to combat rust because of the looks get a winter beater and park your truck during winter. That is the only way to prevent rust. if you are going to drive it threw winter you will get rust. Even if you replace all the fasteners with stainless and do every precautionary measure the body will rot off the frame before the truck gives up the ghost.

                              I have been battling rust for many years with our work trucks. I've tried it all. The best thing you can do is coat everything in waste oil. Don't waste your time and money on futile attempts.
                              Andy

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