The installer said to not run it in 4WD until this has been resolved. That said, I ran in 4WD several times over this past winter and never noticed anything out of the ordinary, other than the clunk in 2WD and 4WD.
I'll be interested to hear what you find on yours. Mine don't seem to move much at all even yanking on them pretty hard, but I don't have great leverage without the wheel off. Looking at the pictures I also don't see a clunk happening with that axle. The axle splines would really have to be slamming hard, and the rusty area just doesn't look worn like it's been moving or rubbing. On the bright side, stock axles don't look too expensive, if they do end up being the problem. I'm going to see if I can get a video of it occurring here at some point. It is easily recreated. I think BDS also has a 2.5 inch coilover lift available now. You might be able to squeeze 33s with that, but it would probably be tight. I have 35s on my 4 inch lift and there was still a lot of trimming to be done. I think my truck looks perfect the way it is set up, but it truly is massive now. If I did it all over again, I'd probably go with the 2.5 inch and some smaller tires. Props to BDS though, when it isn't clunking, the truck drive so smoothly. Doesn't feel like there are 6 inches of lift and 35s for sure.
I don’t think I’m sensitive to it. It is a loud, solid, metal on metal clunk that is audible with windows up and music playing. And it can be felt in the floorboard. It wasn’t this bad initially. I will definitely be taking the wheels off and poking around myself here soon. I’d hope the shop is intelligent enough to have checked all these things already. I’m hoping they aren’t just trying to cover something up, but they’ve never given me reason to doubt. I have the start/stop disabled. The powertrain feels as smooth as day one otherwise.
There is no obvious damage to the CV when looking underneath. It doesn’t really budge when I try and move it. It is on my list of things to do to get the wheels off and go over everything, I had just been hoping the shop would have it taken care of. [emoji17]
The installer has reached out to BDS, I haven’t heard back from them yet. All the suspension components installed are BDS. I’m using the stock Ranchos, not coilovers. I may have been unclear in my terminology, but what they told me is that the splines of the axles are not fully seated in the differential itself. This is causing movement of the axles, especially when turning sharply from a stop or at low speeds. This kit should be designed for the AT4, that is how it is marketed. I really don’t want to do custom axles either. While I realize that every vehicle install is a bit different, this significant of an issue should not be occurring. At this point I am not wary of the installer. They have been very upfront and have done lots of these installs. They are actually an official BDS installer too, which should hopefully make this process easier.
*Disclaimer* - Yes, I know these sort of things happen when modifying vehicles, and I'm not complaining. I have a 2019 GMC AT4, and added the 4" BDS lift last year for a total of 6" of lift. After the initial install, I took the truck back to the installer to check all of the bolts for tightness, and mentioned to them that I was experiencing a front end clunk fairly regularly, especially at low speeds while turning. At the time they brushed it off as new suspension noises. Recently, the clunking has become more regular and is easily reproduced so I brought the truck back to the installer again for a more in-depth look. After some investigation they concluded that the CV axles are not fully seated in the differential anymore. I understand this is a fairly common problem with some lift kits, but I figured with the AT4 axles and a BDS lift touted for what it was, I should be ok. The installer said these new T1 axles do not allow for a spacer like older axles used to, so they have reached out to BDS for possible solutions. While we wait to hear back, I wanted to hear if anyone else with a BDS 4" or 6" lift has experienced anything similar and what, if any, were the solutions. I thought that if this was a common issue, I probably would have heard about it by now, especially with non-AT4 Sierras with different axles not designed for lift. The installer seems to think that at this point there are really two options going forward: BDS provides a solution or I have to get custom length RCV axles made.
This is what they look like in surround view. Notice how the yellow parking lines are not correct, and also my front cameras point a bit low, while the rears point high. That said, if I switch to the front/side view to view the front wheels, I still have a fairly good line of sight. One other potential issue, we both lost our front and rear parking lines. You can see in my picture how there is an hourglass in the top left of the screen. However, they eventually came back for TNAT4, but mine have yet to reappear.
I posted them above. As mentioned before, both of our cameras are misaligned. They still work, but the surround view is rather skewed on the sides. TNAT4 went to his dealer to get reprogramming done, and they were unable to do it without a code from GM. From what I understand, he would have had to buy another set of GM mirrors that come with a code, and there would still be no guarantee that they would be able to reprogram the mirrors I traded him. Maybe he can chime in at some point, but he was looking into having a custom shop fab up a mirror housing that would relocate his cameras to his previously calibrated locations.
2020 GMC Sierra Mirror screenshots are attached, here is a link to the whole electric manual: https://www.gmupfitter.com/files/media/photo/1290/20_Sierra_1500_Electrical_Body_Builder_2019JUN20.pdf I've been told that pin 16, which isn't marked as anything specific, is the rear-facing cargo lamps.
Update: I swapped pins 5 and 13 in my harness and now my tow mirror task lights are functioning normally. As these tow mirrors do not have puddle lights underneath, the integrated parking lights now come on instead of the puddle lamps. TNAT4 and I came to this conclusion based on pin diagrams for our vehicles. He has yet to swap pins on his standard mirrors, but he should regain task light functionality as well. If anyone is interested in the pin diagrams for the 2019 and 2020 GMC trucks, I can post them up. I plan to build and add a 3-wire harness to my truck that will allow the turn signals, parking lamps, and rear cargo lights to function.
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