Alternative to insulation-displacement connector?

Those all-too-common 3M T taps and Scotchloks etc really mess up wiring. 3M connector example They open up the copper strands to ingress of corrosion, and cut a few strands off too.  I have no ideal alternative at this time.

So I follow one of my own two suboptimal methods. I'm interested if anyone has good alternatives.

1. Cut the wire and splice in the new wire to one side then butt splice it back up with Solder Seal Wire Connectors that somehow magically solder with a common heat gun. Remember to put heat shrink on first, doh! I'm saying that to myself...

2. Build my own soldered T tap. Cut insulation in a ring and spread open. Push a sharp probe thru the middle of the original wire, spreading 50% of the strands on both sides and making a hole. Push the new wire into the hole, then twist up tight and solder with a gun or powerful iron. The big problem with this method is lack of weatherproofing. Electrical tape only lasts so long, and there's no way to get heat shrink tube on the original continuous run of wire.

Anybody have a better plan?  I need to wire a flatbed onto my F550 quarry truck soon, so I'm all ears.

I'm not sure I understand your second approach, but since you say you can't get heat shrink on it I don't think I'd use it.

I actually do basically the same thing as your first approach, although not with the Solder Seal Wire Connectors as I've not tried them.  Instead, I take a crimp-style butt connector and cut off the insulation.  Slide the glue-lined heat shrink over the wires and then crimp the connector on.  Then I solder the wires into the connector, slide the heat shrink over that, and heat it up.

Makes for a permanent connection that is waterproof.  And it makes for a much smaller connection than trying to twist the wires together and then solder them.

As for the 3M Scotchlocks, I will NOT use them for all the reasons you stated.  And while they make a weatherproof version, I like my approach much better.

I've done it a few ways. My current go-to is to use a knife to carefully strip a section in the middle of the wire (without cutting it), wrap and solder the new wire to the exposed section of the existing wire, then seal it up with liquid electrical tape. Then conventional tape, heat shrink (if possible) or flexible conduit it over once all wires in the harness getting tapped are complete. Done this when converting to a heated O2 sensor (tapped into the EEC power circuit) and when adding a 7 pin trailer connector (and before that, fixing a poorly tapped 4 pin connector). And tapping the A/C wire when adding an e-fan controller to my ranger.

Takes some knife skill to not cut too many filaments... but it works for me. Used to cut n' crimp but this is a lot easier on tight harnesses (only need enough slack to strip and solder, not to shove and crimp). Plus I find it holds up a lot better. Ford used a similar technique on stock harness taps, only wrapping a crimp between both wires instead of solder; I don't have such crimps or crimper, so solder is my choice.

That is what I have done both on Darth and T2K-CAR. Strip the insulation off where I need to add a circuit take off by using a razor blade. If it is an inside circuit, I generally just wrap it with friction tape, external, like underhood, I have used RTV + friction tape which is pretty much what Ford and Chrysler did.

I have used GM Delco Weather-Pack connectors quite a bit. One thing they don't really offer is a way to splice multiple wires together. However, the more modern successor to Weather-Pack is the Metri-Pack system, which offers splice connectors like this.

https://www.ebay.com/itm/382462410767

I have not tried any Metri-Pack stuff, but it looks like all the same (cheap) tools would work on it. If I ever need to splice multiple wires together, this is how I would do it.

Here is the weatherproof ones Gary mentioned.

https://www.amazon.com/3M-Scotchlok-Electrical-Connector-Self-Stripping/dp/B00P1UENB6/ref=asc_df_B00P1UENB6/?tag=hyprod-20&linkCode=df0&hvadid=241981236908&hvpos=&hvnetw=g&hvrand=846268666226931725&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9023810&hvtargid=pla-381707143677&psc=1

I have been using them on my trailers and such since the 90's. Have not had any issues with them.
Just my opinion. Bruce

In Gary's thread about lighting Positaps were mentioned. I have not used these before but I do have some on hand now:

https://www.amazon.com/Posi-Twist-Bundle-Kit-10-26/dp/B08P9T1SGN/ref=sr_1_1_sspa?crid=11PGMOHXIOQAU&keywords=posi+tap&qid=1636032180&s=industrial&sprefix=postal%2Cindustrial%2C136&sr=1-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzVUFJNEdORkhBVDFCJmVuY3J5cHRlZElkPUEwNjc4MTYyMzQwUDlQNTE5UE1BSyZlbmNyeXB0ZWRBZElkPUEwMzg2MjQ0MlRQU1hJVVVXMFpTNSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

I thought about suggesting those, but the question was about how to "wire a flatbed onto my F550 quarry truck" and I was afraid those won't seal.  Maybe I was wrong?

Please let us know how they work for you.

A flatbed quarry truck is about the worst scenario, other than a salt-water-humidity coastal area.  Although I've reached the stage where I can afford to not run in bad weather, it's still an insistent admixture of abrasive dust and vibration that gets in everywhere. And Texas is known for sudden showers any time of year.

I had a look and imho they would be more appropriate on

1) solid wire so it won't cut a few strands as the edges push thru
2) inside a junction box, as the demo photos show, for additional weatherproofing

I have no junction boxes on my trucks. But heck, some day when I am a millionaire of pure leisure, which is when dogs grow wings, why not do that?  It sure would be a clean look. Along with chrome-plated leaf springs.

3M-Scotchlok-Electrical-Connector-Self-Stripping