Chuchito

After a few weeks, I started my build. First thing to go was the topper. I think it looks good, but since I plant to lower it, it didn't fit the look I was going for. Luckily, I found someone looking for the exact topper so it helped cover some of my project costs.

Hey guys. I recently purchased a 2018 GMC Sierra regular cab short bed. The person I bought it from used it to pull a boat and didn't use it too much before deciding to sell it. It only had a little over 25,000 miles. Here it is with its first car wash.

Not really sure how close to the frame. It looks like it has plenty of room. I haven't bottomed out any, but I have not really driven it too much since I am still working on some modifications in the garage on it. Also, sorry for the late response. For some reason, I am not getting notified when someone comments on this site.

Thank you Mike. I appreciate that. I wish I would have written down all the details of how I was able to do it. It was a lot more wiring than I had hoped. It all turned out great though. I even was able to add power and folding mirrors with turn signals. Replacing the factory door harness with power ones helped out a lot.

Update to the power window conversion. All is installed and working. I did have to add the two relays I mentioned in my previous post. That way there is not worries about amperage issues. I also molded in the aftermarket switches into the factory trim panels in the doors. In the picture attached, the bottom panel is the OEM. The top one is the one where I molded the aftermarket switches. Everything works great.

I just wanted to update on what I have so far for my 2018 GMC Sierra power window conversion. I purchased the door wire harnesses for both driver and passenger door of my regular cab. It looks like those harnesses already have all the wires for the mirrors and power windows. I also purchased used door panels for my truck. Hard lesson on that. The regular cab door panels are NOT the same as the crew cabs. They are a little shorter in length than the crew cab panels. Obviously, my truck does not have the necessary wires on the cab side of connector X500 and X600. I will have to run wires for power to pin 1 and pin 40. Pin 1 is the main thick power wire and 40 is for the mirror power. I will also have to run all the wires for the mirrors so that the switch can connect from driver side to passenger side. The main issue I found is the factory switches. Since my truck does not have the data wire that communicates with the BCM, it seems that the switches need to speak to the BCM somehow. I am not sure exactly how this works and I did tons of research and cannot find any information on how the switches operate. I even called a few companies that specialize in this kind of thing, but they said that its a BCM thing. Based on what I can see, the switches need some kind of a signal to wake them up. I have power and ground to the door harness in my test bench, the window motor is connected to the harness as well. When I use my multimeter to test it, I do not see any changes coming out from the switch itself. I think that there is something in the circuit board that is not activated to allow the switch to work. That's why I think the BCM sends a signal to the switch, activating something in the circuit board to allow it to function. I tried applying power to the green and yellow wire at the switch but nothing happened. I thought that maybe the BCM sends power to the switch but that doesn't seem to be correct. I think it is some type of pulsing signal which I cannot duplicate. Maybe someone "pgamboa" can come up with a device to replicate the function of the BCM to the switch to use as a standalone device to "wake up" the switch. Anyhow, because of the issues with the OEM switches, I think the only way to convert to power windows with the OEM switches is to make sure the data wires are run and connected to the BCM, and program the BCM. For now, I ordered a universal kit from Amazon https://www.amazon.com/dp/B07L162PC5?psc=1&ref=ppx_yo2ov_dt_b_product_details The switches in this kit look very similar to the stock switches. My plan is to somehow modify the door trim that holds the OEM switches to allow the aftermarket switches to mount. Hopefully they look stock enough. Then I will wire these switches with the harness they came with and wire them to the factory door harness to get power and ground. There will be two brown wires in the kit that connect from the drivers side to the passenger side. These wires are normally negative and change to positive when the passenger switch on the driver side door is pressed. This is the only thing that I am a bit concerned about. I will have to pin those two brown wires on both sides of the X500 and X600 connectors. I worry that once I pin them, there might be an issue since the pins don't seem thick enough to handle the amperage that those wires may draw. I will test it like that first and if I see that there is an issue, I may just install two relays on the passenger side door panel to those two brown wires. That way the wires just act as remote wires only to activate the relays in the passenger door. I will update once I get this accomplished.

I just finished installing an adjustable 3/4, 4/6, 5/7 kit on my 2018 regular cab Sierra. I first installed it to be 4/6 but was not happy with the look. Looked to high in the back. I then installed the factory hanger back and it gave me an additional 1-1/4” drop. Now it looks like the front sits a bit higher in the front. Front is Maxtrac 2” spindles with Belltech struts set at 2” drop for a total of 4”. So apparently I am now at a a 4/7.25. I am trying to figure out how to get the front just a little lower without running into rubbing issues.

JamestownMike, were you able to figure this out? I just purchased a 2018 sierra with manual windows and am wanting to do the same you are trying to do. I read the entire post and it looks like you were off to a good start but then it ended. Just curious to know if you finally figured it out.

I just did my 2001 GMC Sierra rcsb and I had the same issue. Your truck does not have the same wiring needed to do a conversion. You need to either come up with your own wiring and setup your own relay setup for the door locks and run all new wire for the windows. Or, you need to get the left and right junction boxes from a donor truck that does have power windows. Run new wire to connect both junction boxes together from one door to the other.