TCM (transmission control) on this CVT (continuously variable automatic transmission) has aluminium soldering that has failed. once fixed comes the problem of resealing the circuit board from the CVT transmission fluid. that can possibly hit 100c. I notice alot of companies that fix it use epoxy. Now i am trying to find out what epoxy that is resistant to corrosive CVT transmission fluid? The few places that reseal after repair seem to use epoxy. (I could be wrong )

https://youtu.be/kPdFR3opLC4?t=646 (after removal look how its sealed after back from repair service) https://www.youtube.com/watch?v=rE1LDfMSY1M gives impression its aluminium wires

The Mercedes w245 .. 722.8 Transmission conductor plate Sounds like uses Aluminium connection. solder points fail. Many who try to fix with regular lead/silver solder and it does not last. I assume a proper fix you need to solder with aluminium flux solder! The oil can get to 80c I used 100c as a example of how high cango. Transmission fluid would be. ATF 28-CVT,type 236.20. I state corrosive (Generally transmission fluid , I may be wrong about CVT fluid) I mention so one knows I am looking for some way to reseal the unit after the soldering so that the fluid does not enter the circuit

  • I will say MUCH improved over previous submit. And some key abbreviations are spelled out. At least we have some idea on whats going on.
    – zipzit
    Dec 9, 2021 at 14:34
  • I don't think in general transmission fluid is corrosive, but then again, I doubt it's good for electronic parts if it were to be in direct contact. Also, consider using Permatex "The Right Stuff". It is made to seal against automotive liquids, and does so VERY WELL. It won't break down under the heat load you're talking about. It also cures up fast enough to use it right away (though gains final cure in about 24 hours, IIRC). Dec 9, 2021 at 16:01
  • I am literally not looking for a gasket maker i need something like (I wish they would tell me) epoxy that they use to seal replacing the plastic all together. Dec 10, 2021 at 3:42
  • Electronically controlled xmissions have their solenoids immersed in xmission oil along with wiring. Valve bodies controlling hydraulic pressures for shifting gears. Nothing unique about plastics and wire insulators in pressure control solenoids. Soldering is low temperature gluing of dissimilar metals like copper wires and low lead/tin solder. Aluminum soldering is actually melting aluminum due to its lower melting point with a similar aluminium rod and flux.
    – F Dryer
    Dec 11, 2021 at 20:20
  • After reviewing the second video, its obvious the epoxy sealed electronics was not meant for repairs. Whatever diy repairs were made, resealing should use the same epoxy or equivalent. Choose epoxy that can withstand xmission operating temperatures. And thoroughly cleaning this circuit board of dirt and oil can help with sealing it against oil infiltration, possibly creating a short circuit condition ruining all your work.
    – F Dryer
    Dec 11, 2021 at 20:29

1 Answer 1


I recommend a oxime curing silicone when sealing automotive electronics. The one I use is Permatex 81173.

On circuit board The larger wires will be silver or aluminum or both. The tiny ones are gold bonding wire.

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