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1996 5.7 high rpm squeal

Discussion in 'GM Powertrain' started by Rbernsdo, Jul 24, 2011.

  1. Rbernsdo

    Rbernsdo New Member

    My 96 Z71 Silverado 1500 has an extremely loud fan and sqeak. I noticed when I got it that the clutch on the fan was actually froze up, so I have replaced the fan clutch, belt, idler pulley and alternator within the last couple months all in searching where this squeak is coming from. When I hammer on it, it sounds good up until about 4500 rpms right before its shifting then it lets out a terrible squeal and the fan is so loud i can barely hear my straight true duals over it. Any idea why A) the fan is so damn loud, or B) the high pitch squeal has not left with the different replacement parts? Thanks.
  2. Ethan

    Ethan New Member

    4500 RPM's is red line for that truck, if it's the 350, they are not meant for high rpms. So, what you're experiencing(if you're actually that abusive to your truck) is prolly normal operation. When you redline a low RPM engine, they tend to not like it.

    The roaring is prolly just the fan, at 4500 rpm, that fan is gonna spin almost as fast as the crank is, so it's gonna roar.
  3. stephan

    stephan New Member 1000 Posts

    Does this squeel only happen with the AC on @ the higher RPMs? If so it could still be the belt or the AC clutch itself. Put everything in heat position (not defrost) & try it.
  4. Rbernsdo

    Rbernsdo New Member

    Thanks for the input, I guess I made it sound like I am beating my truck. That I am not, but when I pull out to pass, hammer the throttle, before it shifts when it is getting up in high RPMS it lets out a loud squeal, that's what I was getting at.
  5. stephan

    stephan New Member 1000 Posts

    No worries RB, 4500 rpms isn't beating it. The 5.7 is good to 5800 with stock valve springs. Did you try it with the AC off? Do you still get the squeal?
  6. Ethan

    Ethan New Member

    ^ Is it really? Cause my 94 350 red lines at 4500 rpm, and has a max of 5000 rpm, according to the manual, and the scan tool.

    It might be some belt sequel. But since you've replaced parts idk. I know there is a TSB on the belt tensioner pulley, saying to replace it with a slightly smaller one.
  7. stephan

    stephan New Member 1000 Posts

    I don't know Ethan. If it says 4500 then I wouldn't go above it, but the weakest valve spring I'm aware of that GM made is good to 5800 before valve float. Maybe GM is trying to reduce the number of engines they have to warranty.
  8. Ethan

    Ethan New Member

    I guess they put a low rpm crank in mine, back when trucks were designed to be trucks, and not racing lol.
  9. Rbernsdo

    Rbernsdo New Member

    I did try it with the ac off and all, i'm just lost in confusion i guess. Sounds kinda stupid but i'm wondering if my truck might have been programmed or chipped modestly because I have been watching a lot of videos and what not of 96 chevy's on youtube and it seems they are all shifting at right under 5k, mine actually has a little bit higher shift points... could higher shift points from a chip or programmer cause the fan to run so damn fast that it chirps at a slightly higher rpm??? when i say slightly higher, i mean like 5000-5100 somewhere in there. And by the way, i'm looking to do a little bit of modification, crank out a few more hp, i know the age old question for chevy truck guys is what are some cheap mods, but seriously haha what are some decent mods for under 1000? My first step is going to be getting a tune up, fix a couple small things that are bothering me (non-engine related) and then look at getting a little more power. Any help would be greatly appreciated, if your paying tax dollars, your paying for my upgrade lol. Thanks!

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