davester

I'd suggest checking the wiring to the bcm, that all the power and grounds are good, and that the data wire between the ecm and bcm is good.

I believe the third connector is used for the harness going to the license plate light. C2(Gray connector) is for left side lights, C3(brown connector) is for license plate, C4(black connector) is for right hand lights. At least, that's how it's described in my '04 Sierra full-service manual. I would suggest going to a junk yard and either getting the harness off a bed (better) or cut off the right connectors and then patch them to your wiring. I don't know if the '09 connectors are the same as the '04 connectors, wouldn't surprise me if they use different connectors.

I believe I managed to replace it without disconnecting the A/C rad (definitely sure of this) or the transmission & PS rads (pretty sure of this). I don't recall if I had to disconnect/drain the main engine coolant radiator (also, pretty sure I didn't disconnect the transmission & oil cooler lines from the rad when I did it).

I believe (again, not certain, as I have a GMT800 truck, and your truck is GMT900) yours works the same as mine, so there is no "auto-locking" hub, like say, Fords have. The hub is solid, and splined, so the short axles with CV joints at each end, always rotate with the wheel. The way GM engineered locking/unlocking the front end, is by using the actuator in the front axle to engage/disengage the passenger side stub axle (inside the front diff assembly) from the diff. So, when the actuator connects the passenger side axle to the diff (ie, 4wd is engaged), then everything works the same as the rear end. When the actuator disconnects the passenger side axle (ie, 2wd), then the passenger side axle just spins as the passenger wheel spins, and the driver's side wheel still spins the axle into the diff, but generally this just spins the spider gears (as it's an open diff).

It was pretty straightforward for me, on my '04 3500 (which is slightly different, as it has a 2" body raise). You want to be careful with handling the 1 or 2 sensors bolted to the bottom of the support, as they are the accident (wrong name, forget the right one) sensors and you don't want to accidentally deploy the airbags... The only difficulty I had was that the radiator support I bought was for a different year, and it had holes for mounting left and right accident sensors, and my truck only had one in the middle, so I added a spot in the middle to mount it so it would be in the same location that it was with the original mount.

If it's similar to the GMT800 manual setup (99-07 Sierras), when you move the shift lever, it rotates a gear in the differential to move things to the appropriate place (hi/lo, 2wd/4wd), and on that gear is a sensor, that notices when you switch between 2wd and 4wd. That sensor controls the front actuator (whether it is retracted for 2wd, or extended for 4wd), and the front actuator has a sensor that notices it's setting and that sensor is what turns the 4wd light on/off in the cab (well, it's hooked up to one of the computers, and that computer forwards the setting to the IP). So, I would say it's either the sensor in the transfer case or a wiring problem (maybe the fuse blew?). Your truck could be different than the setup I've described (yours is a GMT900, and I'm only familiar with GMT800), so I would suggest getting a subscription at alldatadiy.com for your truck, to get access to the full-service manual for it, and go through the testing procedure for this, and that will quickly sort out where the problem is.

brake lines are a common rust problem. Two common places where they rust badly are where 4 of them run along the frame from the front driver's wheel to the abs controller under the cab, and where the rear line runs along the driver's side frame rail above the fuel tank (you may be able to photo graph it using a camera phone). Exhaust manifold bolts breaking off is another common problem.

If there's no TCM code, and given that the transmission is basically new, I would still look at getting the engine working so there's no CEL, and seeing if the transmission still does it. In particular, the upstream O2 sensors are very important to how the engine operates, and if the computer thinks the engine can't/shouldn't produce X amount of power, then it will downshift to reduce the amount of power needed...

Are you sure it's not in OD (as in 1,2,3 & OD)? Or maybe the torque converter doesn't stay locked? And did the mechanic have a code reader that can read TCM codes? And how/when the transmission shifts/locks the tc also depends on how well the engine is running, so you might want to get the engine right before delving into the transmission.

Well, sounds like someone really doesn't want their mind to explode from finding out they might have made a poor decision with how they spend their money. Perhaps you could list some of these billion dollar industries that rely on aftermarket diff covers, and then describe how your specific use of your vehicle corresponds with their use of their vehicles? And again, Banks is going "I don't know how well these things actually work. This is how I will test them and post the results.". As far as I can tell, NONE of the manufacturers of these diff covers have published any kind of test results, let alone detailed how and under what conditions they tested them. They seem to concentrate on "looks cool" (hence the fancy logos/designs in them instead of, say, just cooling fins), and fill/drain ports/dip stick (which can make the job easier/nicer to do).

more fluid does not result in "added cooling". More fluid means it takes longer for the temperature of all the fluid to change (both ways, getting warmer AND getting cooler). And a larger trans cooler likely will make a bigger difference in trans temp vs fins on the trans cover (as it has air flow all the time, and air flow through the cooling stack is more than air under the truck [everyone tries to reduce air going under the truck, as it greatly increases drag on the vehicle]). And what do you mean by "a diff cover designed for handling off-road use"?

They are all plugged (I found a bunch of crap covering the screens in all my old injectors when I replaced them), or the electrical side isn't working. Maybe check that your fuses are all good (check ALL of them, as I've found fuses blown that affect things I wouldn't expect them to), then check if you are getting a signal to one of the injectors (noid light or a better electrical tester than a basic multimeter), then check continuity between the injector electrical plugs and the plug on the ecm.

When I cleaned the throttle-body on my '04 Sierra 3500 w 6.0, I moved the butterfly repeatedly, and cleaned both the body and the back of the butterfly, using TB cleaner and rags/small brushes. Never had any to do any kind of TB calibration and the engine ran ok (I did it as part of figuring out why my truck was running poorly, and I was doing intake & exhaust gaskets, upstream O2 sensors, knock sensors, MAF and MAP sensors, injectors and spark plugs). As for the CD player, you might get one cheap off ebay, but you want to make sure it's not vin-locked. The radio's themselves, once installed in a truck, then become VIN-locked to that truck. The VIN can be cleared from the radio, but it's my understanding that it's primarily a dealer-only process to clear it so it's not cheap. 3rd parties may have figured out how to clear it and do it for less. You might be able to strip some parts from another used one to get yours working again.

Wasn't that hard to add a drain plug to the stock 4l80e pan. I bought a generic drain plug and a nut that fit it, then with the pan off looked at where the drain could go where it wouldn't interfere with internal components, drilled the hole, welded the nut to the inside of the pan and done. Can't wait for the actual test results of the Banks testing...

I would say no, but I don't recall having to crank my truck over for more than a second or two. It surprises me when it doesn't start with a very short blip of the starter. It might be a save-the-engine thing, like no oil pressure, but I don't know. I'm not sure what cranking it longer would do, long crank times were only needed way back with mechanical fuel pumps, if the line was empty, it took awhile to pump the fuel from the tank to the carb, but now with electric fuel pumps, that's not a problem...