jake111

Looks like 2-1/2 years ago I got a ~$14 no-name 604-106 actuator on Amazon, but the particular one I got is no longer available. There are lots of other cheap ones, but maybe read reviews to see which ones seem to hold up. Mine still works fine, and maybe more reliably than the original!!

I'm pretty sure you found the spec in the owners manual was for Dex-III and the Castrol certainly meets that spec. I don't know about the GM transmissions since I have the Allison in my 2004.5 Duramax. For the Allisons in that time era, it was found that the so-called compatible Dex-VI was not compatible with the Allison seals. If your transmission seals are compatible (you'll have to research that), the Dex-VI is fine. But that doesn't mean it's so much better than the Dex-III that it's worth changing out. If you're trying to replace most of the old ATF then it will probably take at least one more drain'n'fill. Each change probably only gets about half of the ATF replaced.

The GM "grapejuice" and the other major brands (I use Mobil 1 Synthetic Gear Lubricant LS 75W-90) already have the proper amount of friction modifiers for the G80. Not enough, or too much, friction modifier will give you unsatisfactory results. I can recommend the Mobil 1 since I've used it for 15 years (over 100k miles) now without any differential problems, or chatter, or other ill behavior or noise.

Since I know exactly what you mean, I guess I have experienced this quite a few times over many years. But, I can't tell you if it was my truck or any number of the other cars I've had or have. I consider it normal. It's possible that I now subconsciously don't put a foot on the brake, or maybe just very lightly, when starting. Maybe somebody else has chased down this "problem"!!

Yep, there are several options as davester listed above. I went with what I think was the first solution, from Merchant Auto which is on the expensive side, but that's what it was 10-ish years ago. Other cheaper pump plates with wide ears are available now. Unfortunately, you have to take the transfer case out and apart to install any of these solutions. And there are some tricks you have to learn to get it apart. (My brother knew the tricks and already had a jig to hold the transfer case, so I don't know details.) The red-neck solution is just to find the pinhole, clean it up, and JB Weld it. Of course, you have to wait for the pinhole!! Or guess where it will be.

davester is correct. ALL of the diesels in 2004 (and similar years at least) with 4wd have a MANUAL transfer case. They came with 2 shifting styles (1) manual shift on the floor, and (2) push button shift (but NOT with an automatic or AWD button). The push button electric shift simply does the same thing as the manual floor shift (you can look at the transfer case). Dex-III is the proper fluid. Since that is officially no longer available, you should be able to find something labeled "for GM 2005 or older" or Dex/Merc ATF. GM "retired" Dex-III and at first claimed Dex-VI was fully compatible, but it isn't, and should NOT be used. The manual transfer case is simple enough that just about any oil will do (some even use engine oil). The expensive auto-trak fluid won't hurt it either, but isn't needed at all. The bigger issue with these transfer cases is "pump rub". The pump is suppose to rub against a hard steel clip in the magnesium tail shaft. Eventually, the steel clip breaks or slip out of position and the pump wears a pinhole in the case. The fluid leaks out over a period of months so it isn't noticed . . . until the transfer case runs dry . . . [added after-thought] There are several "pump rub" kits available to avoid this problem. There are also aluminum tailshafts available.

I'm pretty sure the GM OEM brake pads were ceramic. (19133306-F/19133307-R ?) Might depend on you year.

Yes, usually pads, and especially some 3rd party pads. I would suggest replacing with the genuine GM pads that originally came on the truck. Also, be sure the slide pins move freely and are lubricated (Syl Glide is popular but I haven't used it yet). Also, the pads need to move ("float") in the brackets (not tight, but not loose) and with just a dab of brake grease. I'm not sure about the rotors. They should be ok unless they have any coating from the old pads (and of course, aren't worn too thin or warped).

More important than what it says on the door, or what anybody else does . . . what does it say on the tires is the maximum pressure? If it's Load Range E, it probably says 80 psi; if it's Load Range D it probably says 65 psi. If the tire says less than that, it's probably not the right tire for your truck. Those are the MAXIMUM cold pressure ratings. If you are towing or hauling then you probably want to be at or near the maximum. If driving around otherwise, something less will soften the ride, improve handling, and help wear evenly. How much less? Watch for tire wear. It's like the 3 bears. If it wears in the middle, then the tire pressure is too high (papa bear, too hard). If it wears on the 2 outside edges, then the tire pressure is too low (mama bear, too soft). If it wears evenly, then it's just right (baby bear). If it wears just on the inside or outside edge, then it's an alignment problem. Oh, and don't go rotating tires every 5k miles or you won't have a chance to see the wear pattern. (Revealing my belief that the 5k mile rotation is pushed by tire dealers to cover up problems.)

The 5-speed Allison has PRND321 on the shifter. Press/hold the T/H button for a few seconds and you should get a D-with-slash on the cluster display, aka overdrive lockout. Press/hold the T/H button for a few seconds to re-engage 5th. They used this instead of a "4" on the shifter. When you count shifts it may feel like it's a 6-speed, but one of them is the torque converter locking up.

What speed is the 5-4 shift? Are you in Tow/Haul mode or normal? If not in T/H mode then it sounded like just the torque convert relocking. I am only experienced with the 5-speed Allison with a Duramax, but in non-T/H mode the lockup is right around 48 mph (higher if under load).

For many years people thought the problem was the intermediate shaft. It seemed partly to blame for the clunk. The current consensus is that it's the plastic bearing on the steering shaft, under the dash. There were descriptions of an improved green plastic bearing. If you've read up on it, you've also run into zip ties, hose clamps, and muffler clamps that pull the shaft to one side instead of rattling around. I think I put a zip tie on mine years ago and since then, I just ignore any clunks. I accept it as "a GM thing". Sorry, I have nothing to say about vagueness. A couple of years ago I had a steering box put in, but that was because it was leaking. Other than that I haven't needed any front end work, except shocks and a heavier-duty sway bar, and I adjusted toe to eliminate some edge-wear on the tires.

I'm not positive about our trucks, but for most (all?) vehicles just disconnect the light sensor on top of the dash. Yes, I know "just disconnect" might not be the easiest thing to do . . . unless you're willing to burn your bridges and destroy it from above.

With 4wd, you need to be aware of the "pump rub" issue in the magnesium tail section of the transfer case. It can cause a pinhole in the tail section, very slowly leak out the ATF (in the transfer case), and ruin it. There are various pump rub kits, or if a tail section is ruined there are aluminum replacements. I don't live in a cold climate, so I'm certainly no expert about winter prep. Bio-diesel is very good for the motor but gels much quicker in cold weather. Avoid it in the winter if you can. You'll have to study up on anti-gel additives (like Diesel Kleen 911, I think), and using Diesel #1. The glow plugs and controller need to work well in cold weather. Turn key on, wait for glow plug light to go off (should be about 5-10 seconds in cold weather, I think). I always suggest a lift pump and more/bigger fuel filtering and water separation. I use a Kennedy Diesel lift pump and Donaldson filter on a Nicktane auxiliary filter head. Beware that some setups flow too much and cause problems with the return into the tank, so be sure to read reviews on the so-called "bigger, better pumps". I assume you know that the LB7's had problems with the injectors. Again, there's lots to read on that, too. Again, I'm lacking experience with the LB7 since I have an LLY with it's own list of potential problems!!

While it costs more than rebuilding, many have had better results with just replacing with a new unit. I replaced mine with one made for 2011 (ACDelco 178-0853). It may require a little bit of filing on the rod eyelet so the brake light switch works properly, but there was also a significant improvement in my brakes. Read reviews for that by others, not just me (Amazon and elsewhere).