The King - a 2002 GMC Yukon XL... 496 CI of STILL not an LS!

ck80

Comic Book Super Hero
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Feb 18, 2014
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I run 285s on my 1500 with some front crank and rear 2500 springs. Pretty sure the 8 lugs take them with zero mods.
Yeah, what I've been reading online was that 285s are about the limit for no rubbing without cranking the keys and adding blocks in back. And let's face it, this isn't a fuel efficient ride.

I saw one for sale a couple weeks ago that had something interesting though. Apparently gear vendors sells a double overdrive unit that's intended to be used as such. And it's meant to be used with 4x4. It wasn't something they had on their websites last time I was there but that had been a long time ago. Went there after seeing the truck and yes, it's a thing.

I guess you switch it on once up to highway speed. Couple mpg on a pig is a 15-20% improvement so you make your money back quicker.
 

ck80

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Feb 18, 2014
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Well, its been a month since the a/c charge... well, maybe more like 6 weeks. Outside air has been 95-100* with 60-70% humidity outside air lately. Needless to say the truck didn't feel as cold as it did earlier, humidity being higher.


Right now outside air is 98* with 62% humidity per the weather service. Underwood component temp is obviously higher being in the sun and with engine throwing heat.

Static is only 80psi equalized. I've read around 120 is a good target for this weather.

With it engaged its cool, not cold, and runs about 60psi low side and 250psi high.

So, it looks to have a slow leak somewhere, which is fine. It probably needs a can, or portion of one. That's fine. If it's $3/month in r134a I can do that, that's less than the oil it drinks costs. Then in cold weather season I can mess with it and take it apart.
 

ck80

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Feb 18, 2014
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What are your discharge temps?
My "good" digital thermostat is, of course dead. Using one from the house just to get a rough benchmark showed discharge temps around 78ish on an analog thermometer I didn't trust to get a couple inches inside the ductwork.

This would've been in the sun because sun is everywhere, with likely higher ambient temps on the pavement and in engine bay than what the official weather has.

So it's only cooling 20-something degrees from external. Running it a while no frost up on any return lines either.
 

Supercharged111

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Oct 25, 2019
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Colorado Springs, CO
Oh damn, mine will blow in the 40s even when it's hot out. It may take a few minutes to get there, but they do. Definitely dump another can in there, when it blows cold it'll drag the low side pressure back down. The supercharged dually blows so cold it'll freeze itself up! I should stick the gauge in that one, it must be down in the 30s. Can't run the fan too low on a long road trip, but if you run it too high it'll freeze you right out. Not even the Envoy can match it.
 

ck80

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Feb 18, 2014
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Sigh.

More bad luck on the horizon. Today on a trip back from lowes the "check oil level" message displayed in the vehicle information center while the better half was driving it. It had an oil change with the proper amount of oil just a couple weeks ago.

No leaks underneath. No spots on the driveway. I hear there's an o-ring on the pressure sensor that can go and allow air into system and make issues. Could also be a bad sensor. Obviously wouldn't do any good to check it hot when she got home so it's parked until the morning.

She took a shot vid and showed the usual 30psi idle and 50-60psi driving depending on throttle.

It'll get another change tomorrow to see what's in there for the heck of it anyways. I know the oil pressure send unit is a pita to get to, need to remove the fuel rail and upper intake cover then do a job by feel only on the back of the block near the firewall. Beyond that, if it is an internal mess or it did lose pressure some how and left metal in the pan... well, maybe I'll just not get the toy the wife offered and say f*** it, get the raylar 540 stroked engine with forged bottom end and make a monster out of it. They've got a twin screw blower kit too. I bet I could get both to our door under 10k and push 800+ hp according to their dyno sheets.

New stuff is nice. We'll learn more tomorrow.
 
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Texas82GP

Just-a-worm
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Apr 3, 2015
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Spring, Texas
Does it have an in-pan oil level sensor? Many engines of that time did, like my LT1. I wouldn't get to concerned if that's the case.
 

ck80

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Feb 18, 2014
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Check oil level doesn't sound as bad as zero oil pressure. They can definitely drink oil, how many miles and how much oil was gone?
Whelp, the issue just happened/I learned of it right before the post I made. She parked it and I didn't bother checking the dipstick since it was hot. I'll find out when I drain it in the morning.

Miles are only 134k or so now. Oil change only had about 300 miles on it though, and everything was tight- plug, filter, etc. Thats as far as I looked with it hot and all..
Does it have an in-pan oil level sensor? Many engines of that time did, like my LT1. I wouldn't get to concerned if that's the case.
I believe so. I really wasn't in the mood to deal with it tonight so didn't double check that one. I know where the pressure one was, which, if the oil is really low perhaps the pressure sensor is also not reading right (as in how could it maintain a healthy pressure if the level was toast), but I didn't double check the level sensor location. It would be opposite side from where I went under the truck to double check the filter and plug and started to get mosquito bites so I gave up. (Garage was full and also too lazy to shuffle vehicles around to pull it in when I can just deal with it in the morning.)

What I'm not sure about is if/how the message center in these gmt800s might treat a double fault... as in, if the message generates for low level, would it also alert for low pressure and alternate? Or does just the first message display.

Had the wife told me AS it happened, I'd have told her pull over, shut it off, and I'd come dump some extra oil in just in case. Or let aaa tow it home. At least she only drove it across town about 10 minutes like that so it could be worse. Which is half the reason for draining the oil just to see exactly how much is there, if low did she do any damage if the pressure sensor was wrong or not showing correct... meh, who knows. Tomorrow will tell. Glitter in some very low oil would make me mad though.

Since we've owned it I've done 2 oil changes so far. It seems to use less than 1/2 qt every roughly 5k miles or so which is pretty good for these 496s.
 

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