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300 Blackout

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About 300 Blackout

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  1. There were three options for the original gear ratio. If your truck came with 3.42 or 3.73 from the factory, it’s an easy swap. If it came with 3.08 there’s a couple extra parts you need to make it work but it’s still doable. I recommend going to 4.56 or 4.88. Since you have a 2wd truck, upgrading your driveshaft is an absolute must if you ever want to drive at highway speeds. The driveshaft on your vehicle is longer than the 4wd trucks and its going to be dangerously close to it’s critical rotational speed. Also plan on some sort of a tuner in order to update the computer for your tire size and gear ratio.
  2. A quick fix that you may want to read about is unplugging the brake booster vacuum sensor. You’ll get a warning about servicing the brakes/booster, maybe a MIL, but as far as I’ve read, it won’t allow the truck to enter AFM and won’t impact the operation of your brakes. I don’t have any first hand experience with this method but quite a few people out there have posted about it.
  3. I used AutoAnything’s house brand “TruXP” tuner to turn off my AFM. It was $200 and turns out it’s a rebranded SuperChips tuner. (TruXP didn’t offer a Mac compatible software updater, so I went to SuperChips website and used theirs to update my device). Aside from being able to turn off AFM, I like the other options that come along with having a canned tuner rather than a dedicated AFM delete device, however, I’m out of warranty so I don’t mind making use of those extra features. Unless you personally examined the cam, I wouldn’t be so sure it wasn’t damaged. I can think of at least one member here who had the exact same problem. He finally pulled his cam sometime after the repair and found it was damaged after all. Even if you were to mechanically delete the AFM parts, you still need to turn it off in the computer. Melling has a video which contests the theory that the lifters are the cause of the failure. They explain it’s a VLOM/programming issue which causes the lifters to collapse. If it were me, I’d just turn off AFM on the computer and start researching what performance cam I want to install at 72,001 miles.
  4. What did they lube? If the lube stopped the issue, even temporarily, then those parts are a good place to looking for the problem. There are a lot of possibilities. Ball joints, tie rods, CV shafts and steering rack to name a few. If you’re lifted or leveled, give a good hard look at your steering rack by unclamping the boots and sliding them out of the way then turning from side to side. There’s plenty of threads on the net about rack failures. Other possibilities include loose front suspension bolts, worn sway bar bushings and links and even leaf springs have been identified as causing a popping noise while turning. Good luck. Sent from my iPhone using Tapatalk
  5. Below is a picture of the thermostat housing disconnected from the trans. The bottom port is the output from your transmission to your trans cooler. The top port is the return from the cooler and back into the trans. I let my truck sit overnight and the trans fluid was 80*F when I disconnected my top line from the thermostat housing (thermostat still connected to the truck) to flush out some fluid during a complete fluid and filter replacement. Even though the fluid was at ambient temperature, the return line flowed trans fluid. My truck had 75k miles and I decided to replace the trans cooler lines (which includes a new thermostat and housing) as part of my service interval. Before installing the new lines, I opened up the thermostat housing, flipped the thermostat upside down per some directions I found online and reinstalled everything. I cleaned the pan, replaced the filter, fluid and pan gasket. My trans temps have dropped by 20 to 30 degrees. I’m averaging about 160 while cruising on the highway in 80 degree weather. Now, if my truck was within the warranty period like yours is, I would take video and pictures of my trans temp readings along with pictures of the driving conditions, outside temperature reading on the dash and of the vehicle to show that nothing is being towed. I would then bring the truck back to the dealer with a written explanation of the problem and would attach the pictures along with copies of the previous work orders when they couldn’t find or fix the problem. Then, I’d reach out to GM customer care and provide them with everything you provided the dealer and ask them to assist in making sure the problem is resolved promptly. I’m not saying the dealer is incompetent or that you should be rude. It’s possible they couldn’t reproduce the issue. Just remove any legitimate excuse for them not fixing the problem and get some oversight involved that doesn’t fall under the chain of command of the dealer. Good luck.
  6. Love this build. You’ve chosen many of the same products I’ve been looking at. Would love to hear some feedback about the Deaver U182 springs. I have 4.56 gears with 33”-34” tires. I recommend you go shorter than 4.10s. Either 4.56 or 4.88 with your tire size. My highway RPMs are only 2250 at 70mph. The gears alone make you feel like you have a blower. Maybe I missed seeing a driveshaft listed on your build. If you haven’t upgraded it yet, I’d start looking. I went with a one piece 5” aluminum shaft. Some guys like the two piece shafts. Love watching this build. Thanks for sharing.
  7. Grumpy gave some great feedback. I don’t know all of the reasons why manufacturers choose the materials, maintenance intervals, etc.. that they do. I think it’s safe to assume “reasonable lifespan” or “reasonable amount of maintenance” is somewhere in the mix. Thankfully, I’m not a “reasonable” kind of guy. I expect more and am willing to do more to get it. :-) The 6L80 is a great transmission. If you’re goal is absolute longevity, decreasing time between your fluid change intervals, decreasing the fluid operating temperature by modifying your trans thermostat (very easy to do) and driving the truck gingerly will have a tremendous impact on how long it lasts. I absolutely think 250k+ is achievable before a rebuild.
  8. I just re-read you post and see the info about the plugs. I also overlooked the part about being it’s worst at 30mph and feeling like a failure AFM to properly engage. You could have a lifter problem if it’s occurring specifically when the AFM kicks on or off. Lifter collapse is a known problem on the AFM cylinders. I hope this isn’t the case since it’s not a cheap fix. It might be worth pulling your valve covers and evaluating your valve train to look for a collapsed lifter.
  9. What modifications have you done to the vehicle? Was any recent work performed on it? Even if nothing was fixed, has anything been removed, loosened or unplugged recently? What did your old spark plugs look like? Black and greasy? Grey? Pitted? The fact that it doesn’t occur under heavy load suggests a manifold vacuum leak. Since vacuum is highest at low RPM, if unmetered air is getting in, you may be going lean enough to cause a misfire. At wide open throttle, manifold vacuum is low and your fuel ratio would richen. Both conditions might decrease the impact of a small manifold leak. Not saying this is the problem, but it’s something to consider. Another possible cause is your oxygen sensors. If you haven’t replaced your oxygen sensors yet, they are long overdue. I’d purchase and replace all four of them at the same time before investigating the issue any further. They have a big impact on your AFR and if they are providing the ECM faulty data, you’re going to be chasing your tail trying to troubleshoot the issue. If it were a problem with the injectors or fuel system, such as a clogged or failing injector or pump, it would seem the problem would get worse as the demand for fuel increases like it would under heavy load. (There are others here with more knowledge about the fuel system than I and they may chime in with more useful information). The same goes for the ignition system. As more air and fuel enter the cylinder the more likely a weak spark would result in a misfire compared to at lower RPM. Dirty intake valves may be contributing to the problem. If it were my truck, and I was still having problems after I had already addressed the other issues above, I’d pull the intake manifold and look at the intake valves before squirting anything on them. It’s not that difficult, especially if you spend $20 and buy the Haynes manual that takes you through it step by step. If the valves are so dirty to obstruct the intake air flow, enough to cause a misfire, you may create a much bigger problem if you dislodge that carbon buildup and it’s ingested into the cylinder. The sprays have their purpose and place, but I wouldn’t do it if I suspected large chunks of carbon were casing an obstruction. If you find large amounts of carbon on the valves, you can pull the heads and clean them manually or you can media blast them in place through the intake ports. Other people have had success by soaking them in solvent through the intake ports also. All of these remedies require a meticulous approach to assure nothing enters the combustion chamber that shouldn’t be there. Not every misfire causes a MIL. It’s recorded somewhere, you just need the right scanner to find the data. Good luck finding the problem. Please post a follow up once the issue is resolved to let us know what it was.
  10. I replaced my plugs just prior to the noise starting. I didn’t torque it enough and it backed out. I’m not sure about the plug gap causing a knock. The fuel won’t spray into the spark. The ECM regulates the injector pulse width to prevent this, if that’s what you’re asking. I never had a MIL come on, and it really only needed half a turn before it was snugged back up. I’ve fixed a ton of my creaks and squeaks. One of the biggest offenders was my brakes. I replaced calipers, rotors, pads and cleaned the hell out of the parking brake components along with lube in the right spots. Whisper quiet. I used Super Lube spray in between my leafs and that eliminated the creaking I was experiencing from them. I got rid of my mechanical vacuum pump, turned off V4, and now pull vacuum from the intake manifold. No more choo-choo train. I just finished sound deadening the entire truck interior with KilMat and neoprene. It’s down to 76 dB(a) at highway speeds 2250 rpm. That’s with long tube headers, dual exhaust and no baffle mufflers dumped before the rear wheel. When I sound proofed the truck, I addressed a lot of the plastic panels that squeak. The center console in particular was the main offender. The trim panels (immediately next to your right thigh) were very loud. I removed them, applied strips of butyl rubber and then smothered the contact points with Super Lube grease. When I reassembled, I put a small piece of plastic at the front most corner of the trim panel, near where it meets the dash board. No more squeaks. As for the sewing machine of the direct inject engine, well that’s an easy fix; long tube headers and a dual exhaust. Bye bye sewing machine, hello happiness.
  11. Check that your spark plugs are fully screwed in and seated. I had a very similar noise and was really was worried about it. Turns out my cylinder 5 spark plug backed out a little. Not enough to cause a misfire or check engine light, but the sound had me convinced I was gonna have to put a new cam in it. Tightened the plug and the noise disappeared.
  12. I’ve been eyeing this one for some time. You only need one welded adjacent to your drive shaft. Just make sure your pinion angle is properly set before welding it in place. http://www.chassisunlimited.com/product/link-suspension-kits/traction-bar-kit.html
  13. There’s a lot of options for trans fluid. Any new DEXRON VI fluid will be an improvement over used fluid. There are also fluids out there that aren’t certified/licensed as DEXRON VI but are more than capable of great performance in our transmissions. I have the 6L80 also and I used Amsoil Signature Series Fuel-Efficient ATF. I bought four gallons since I also changed my transfer case fluid (do that too if you haven’t already) and wanted to have extra on hand. I didn’t do any reprogramming of my trans after the fluid change, but I did disconnect my battery negative for other reasons which may have forced the trans control module to relearn it’s settings. Either way, over 1,000 miles and the trans couldn’t be happier. Shifts great, stays cool and is still nice and quiet. It’s a lot of work but well worth it for the longevity of the truck.
  14. Absolutely drop the pan, clean the magnet and change the filter. Don’t worry about changing the filter seal if you don’t have a seal puller. Just change the filter with the old seal in place. Yeah, it’s not perfect but it’s better than leaving the old filter in place and not dropping the pan. Make sure you pre-lube the o-rings before seating the new filter. If you are methodical and plan for 2-3 hours, you’ll be happy you did it. Make sure plan on having extra fluid to “waste” in order to flush the converter via the cooler lines. Well worth it. Here’s my pan and fluid after 75k. The magnet was coated in shavings also.
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