abominable z71

I can't find anywhere what it's used for. I originally put a wire in my harness to connect it. I then tapped a run1/ign source from inside the cab and ran it to the headlight just for testing purposes. Long story short the headlights didn't behave any differently with it connected or not so i'm not sure what it's there for, I don't believe it does anything. While looking at different T4L headlights on ebay there were a few pictures posted of the male connector on the back of the headlight. And some of them only had 6 or 7 pins instead of all 8, and the pins that were missing were the bulb out and run1/ign pins. The diagrams for the 2016 only show this wire on the pinouts for the headlights and the fuse block connector as circuit 3139 but it never shows up in any of the wiring diagrams including the pinouts for the LED controllers. now the 2017 upfitters diagrams are out and it's shown in the headlight diagram both lights are fed from the same 10 amp fuse in the underhood block and it shows circuit 3139 going into the LED controllers but only on the LED headlights in the sierra not the silverado and not into the HID version of either.

That ground wire is for the entire head assy. If you had an issue on that wire you would have problems on all lights, Park/Turn/DRL/Low beam/High beam. inside of the head assy is a junction where all the grounds come together and exit the head light via pin 1. Pin is connect to the original delphi 280 connector by the adapter harness you got from Vann. From the original connector on pin a the ground wire runs down to the frame location. it sounds like you have a problem with power jumping across from the turn signal to the DRL wire. They share a wiring harness from the fuse block down to the x110 connector. Other wise the DRL and turn signal are different harnesses out of the BCM to fuse block. I have attached a wiring diagram I made while researching and building my harnesses. Not sure if it'll help much. HEADLIGHT WIRE DIAGRAM LEFT.pdf HEADLIGHT WIRE DIAGRAM LEFT.pdf HEADLIGHT WIRE DIAGRAM LEFT.pdf HEADLIGHT WIRE DIAGRAM LEFT.pdf

If i'm understanding you correctly He swapped the entire head light assembly with another one and it still has a flickering issue? Loose connection in the GT 280 female plug on the truck side of the harness or further up the chain back to the fuse box or BCM. These LED's are way more sensitive to loose connections than resistance bulbs.

Sounds like it may be an issue with the controller module. Gm gives them 2 different part numbers K166L and K166R. These are the heat sink looking things on the back of the light. Here's one thing I discovered while installing mine expanding on what Vann found while testing his. Without a minimum of a 4700 uF capacitor on the low beam the light functioned fine while the truck was off and being powered strictly by the 12v DC battery, once the truck was started the light would flicker after about 5 seconds then come back on after about a minute and work fine from that point until the truck was shut off and restarted. The problem is with the alternator making ac current and rectifying back to DC, the power just isn't clean enough until the truck has run for a bit and the cap smooths it out to prevent this. While I never saw an issue with the DRL's this might be the case. Perhaps putting a 4700 uF cap on the DRL would prevent this it might not need to be this large for the DRL maybe a 2200 would work but a 4700 should do it? Although my money would be on the K166L controller as the issue. you can find them on ebay.

On ebay I paid 500 and 535. The left side had some scratches but I was able to polish those out with some elbow grease and re coat the head light with UV protectent from sylvania. They look good as new when re finished. Looking more in the 750 plus per side range if you want them in perfect condition.

I made some progress on the DRL cutoff but ran into a question of the way the lights work at night. i'll try and break down the answer I'm looking for. Factory function- known: During the day the DRL circuit is energized only when the truck is in drive. With the truck in drive DRL's on and turn signal on, the DRL shuts off. known: Day or night with Truck in park and headlights or park lamps on. The parking light circuit is energized for the C's and stay lit even with the turn signal on, I have found videos showing this functionality. Unknown: Day or night with the Truck in drive and headlights or park lights on. Does the park circuit in the C cut off when the turn signal is on or stay lit? I believe it stays illuminated and only the DRL cut's off with the turn signals. Can anyone verify this?

Seriously, It's like saying you have cancer and know the cure but would rather die than tell anyone or even cure yourself. Why even bother coming onto the forum if you have nothing constructive to offer.

Ask farml1234 apparently he knows the cause, but won't even fix it on his own truck.

This is probably due to your truck being an SLE and not having the original DRL wire. Is this how you installed the harness? Gen5DIY silveradosierraheadlightharness.pdf Thanks Vann Gen5DIY silveradosierraheadlightharness.pdf Gen5DIY silveradosierraheadlightharness.pdf Gen5DIY silveradosierraheadlightharness.pdf

I haven't messed with it because I'm still looking for a passenger side in good shape for a decent price. 700 is about the cheapest. I paid 500 for the drivers side in excellent condition. I think more people know you can swap them so now there is more demand for them. They used to pop up on ebay pretty often but nothing lately. I thought about buying a chrome one and opening it up and painting the chrome black to match but don't really want to go down that road so I scour the internet daily looking for a good deal on another light.

When the headlights are on is the C dimmed or same brightness as during the day ?

You have 4 options off - auto - park - on Off - All lights off including DRL Auto - C is on as DRL at full brightness during day while truck in drive, headlights turn on automatically with sensor, when the headlights turn on the C will dim. Park - C is on as park lamp dimmed, side clearance light is on headlights are off. On - C is on and dimmed clearance light is on headlights are on. There is no way not even on 2016 to turn just the C on at full brightness with the factory wiring and controls. A custom wiring job and separate switch would be required. I' not familiar with the wiring harness for the 2015 SLE but it originally didn't have DRL LED's so it likely doesn't have a separate DRL wire as the DRL function was integrated in the headlight itself. I'm not sure the method Gen5 used to get around this to activate the DRL during the day without turning on the headlight bulbs. Did you install the harnesses yourself and did they require additional wiring beyond just being plug and play?

Are you talking about the internal lens for the C warping due to heat?

Just got a set for my buddy, I wish i would have waited on mine could have saved 30 bucks. oh well so goes life. thanks Tim.

Exactly the problem, tolerance stack that creates a vibration that matches the natural frequency of the truck at particular speeds which then resonates through the unforgiving frame. The problem is the vibration at least in my case and probably others is third order tire which isn't caused by a simple mass imbalance. Mass imbalance causes first order vibrations. It's why the problem isn't corrected by balancing. My tires are all road forced to below 10 lbs and the truck still shakes. What do you believe is causing the front end to shake?

Preload torque on the pinion nut is extremely light usually around 10-12 in-lbs. That's IN-LBS not ft-lbs. That being said too light of preload creates backlash problems and can usually be heard when decelerating.

Got mine put in this weekend, Definitely worth the money. Tim add me to the list for one set, my buddy wants a set for his GMC and I told him about the group buy you got going.

klearz.com/products/gmc/2016_sierra_headlight_markers this link has a few 16 lights that have been painted. They open up the same as the 15s

Good looking out on the coupon code, just ordered a set.

Some people have said towing a trailer or having a decent load in the bed like an ATV/snowmobile actually makes the vibration worse.

The problem with mules is so few are made the parts they are built from are held to much tighter tolerances. It isn't til mass production that components pushing the edge of the tolerances are made and then you find your issues. It's a problem inherent in prototyping you can't catch issues that will arise during mass production. However; GM should have figured it out well before the 2015 MY runs considering this issue popped up in late 2013. Which is why many speculate they know what causes it but the fix was too much money.

Density stays the same, density is just weight per unit volume which like wrench said is a physical property of material. Clamping the spring just changes the K value of the spring pack as a whole. The springs are designed to progressively load first spring flexes until making contact with the second then both springs flex together giving a softer ride, small bumps are handled by a single spring, larger bumps by both springs together. By clamping them you have taken the progression out making them stiffer. The clamped together stiffer pack now has less displacement per the same force applied with the spring not clamped which helps the pinion angle because the springs provide the opposing force when torque is applied to the rear end. If the goal is to control pinion angle you're better off clamping the springs together behind the axle, when torque is applied to the wheels for forward motion the pinion flange will tip up creating an opposing torque to the tires so the portion of the leafs in front of the axle compress together and the portion of the leafs behind the axle separate, by clamping the rear portion together you eliminate this separation when torque is applied. This is how the cal tracs work and why they are mounted to the rear, they also take it one step further by linking them back to the axle with a strut that loads in tension. So for controlling road input clamps in the front or rear doesn't make a difference but for pinion angle the rear is a better location, either location like 2 stroke said the trade off is going to be a stiffer ride.

I covered my entire floorboard and cab behind the rear seat with stinger roadkill as heavy as that stuff is it doesn't have enough mass to change the natural frequency enough to get it out of resonance what does help cold weather below 40 degrees all the rubber is stiffer in the colder temps and rain also mitigates the vibes when everything on the truck is wet.

After a little more research, this is actually the LED controller GM has it labeled as the K166L and K166R LED controller if you remove it you will see a 20 pin connector. The case functions as a heat sink as well but the brains are inside of there.

It is possible but like mentioned above if you do it yourself you have to seal the rear out put otherwise the t-case pukes out transmission fluid. Not sure how you're supposed to seal it up to prevent this, maybe there is a special part GM has that replaces the stub shaft that slides into the transfer case. You could remove the stub shaft from the drive line by pressing out the u-joint and slide it back into the t-case but I don't see how you would prevent it from falling out without the drive line to hold it in that would really suck for it to fall out at 70mph on the freeway, for you and whoever is behind you on the road, it's designed to slide in and out as the suspension cycles so there is no keeper holding it in. The front drive shaft doesn't turn when in 2wd only the front CV shafts are rotating while in 2wd.