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jake111

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Everything posted by jake111

  1. 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.
  2. 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.
  3. 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"!!
  4. 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.
  5. 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.
  6. I'm pretty sure the GM OEM brake pads were ceramic. (19133306-F/19133307-R ?) Might depend on you year.
  7. 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).
  8. 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.)
  9. 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.
  10. 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).
  11. 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.
  12. 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.
  13. 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!!
  14. 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).
  15. All of the above . . . plus try new bulbs. Sometimes when they "burn out" the filament jumps over to another filament and strange things happen. Sometimes you can't tell just by looking at the bulb, either.
  16. Blend door actuators? Notorious for going bad. I just replaced one, but it was the easy one which just put heat to the driver side all the time. Rat nest? Other debris like leaves in the vents? But sorry, I don't know where to start looking...
  17. Basically, the "something special" you need is ... a Duramax pickup truck. Then move whatever it is that you really like from your old truck to the Duramax truck (if that something is compatible). Maybe you can get davester to help you He already knows how to convert from 2wd to 4wd!!
  18. Almost always it's a loss of prime. Try priming it (hopefully you know how). If the filter head hasn't been rebuilt or replaced in the last few years, it's probably leaking air. Also, the soft fuel lines are getting old and leaky. Sometimes even the hard lines are rusting, and sometimes from the inside out. If you don't have a lift pump, the pump on the engine sucks fuel all the way from the tank and through the filter. A "leak" anywhere will cause a loss of prime. I say "leak" in quotes because air leaks in and fuel does not (usually) leak out at all.
  19. Certainly sounds like a stepper motor. While a more common problem in the older trucks (I replaced all of mine years ago), it seems like any stepper motor can go bad. If you have something that plugs into the OBDII port and displays stuff, you could watch the speedometer speeds shown there. If they look good there, then it suggests the stepper motor for sure.
  20. As long as whatever you are doing doesn't cause jerks or clunks, then it's fine. By that, I mean (for a Duramax, but I'm sure similar for you), for me, between about 28-48 mph the torque converter is locked up in T/H, but unlocked if not in T/H (generally). If I am under slight acceleration/load and switch out of T/H in that range, the drivetrain gets a jerk/clunk. So I don't do that. I don't think it's as touchy engaging T/H in that speed range, but still I make sure there's no load so the transition is as gentle as possible.
  21. My fuel gauge started pointing down when the stepper motor went bad (like 10 years ago). Pretty common for any of the stepper motors to go bad (often the speedometer). If so, replace all of them at the same time.
  22. Of course!! [On edit] Ok, maybe I should qualify that a little. You probably shouldn't shift to a lower gear that would cause the engine RPMs to go above redline. But I also think the computers are going to protect the engine from doing that anyway; still, why test it? I guess you shouldn't be shifting it every 2 seconds, either, but I don't think that was your question.
  23. 2004 was a transition year from 1st gen (LB7) to 2nd gen (LLY). Look at the RPO codes in the glove box to see. Each has their own distinct list of issues. Maybe the biggest for each: LB7 - injectors (1st set were probably replaced under warranty). LLY - overheating (towing up long grades, especially in the west); injector connectors (#2 and #7 notorious; but the injectors hold up very well!); headgaskets (especially if overheated or had tuner). I usually recommend the LLY (I have one) only for people who are likely to work on it themselves (maintenance, looking at known potential problem areas). Regardless, if it's had a tuner I would walk away. I hate that it sounds like I am trying to scare anyone away from these trucks. I've had mine since new and plan to keep it "forever" because it's a GREAT truck (but I've taken steps to prevent overheating, worked on the #2 and #7 connectors, protected the known wire rub-thru spots, etc.).
  24. As others have said, the G80 is sensitive to having some friction modifiers, not too much and not too little. It does have clutches that engage the locker. Use either genuine GM grape juice, or I've been using Mobil 1 synthetic gear oil, 75-90 that says "LS" on it, for a long time without any issues. Unless the Lucas specifically says it has friction modifiers for limited slip, then the G80 is definitely going to chatter. Or they might be the wrong modifiers. Stick with what's known to work well!!
  25. A search reveals this thread (on this forum), and the last few posts talk about removal:
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