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New Owner - Questions - MPG and Performance

BOP Racer

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BOP Racer Enthusiast

BOP Racer

Posted
Posted

Hey guys,

 

I'm new here, and I'm also a new owner in the late-model GM truck realm.

 

I just bought a '00 Yukon XL SLE, 58k miles. I'm not kidding when I tell you that there is not a spot on the interior or exterior! Beautiful shape. It was a company lease vehicle in Texas.

 

I have some questions. I could dig through 238 pages here to find them, but I thought you all could point me in the right direction at least. Please?

 

1. How do I find out what rear gear I have? Is it printed somewhere or do I have to jack it up and count? Will it have a tag on the diff if it's a posi?

 

2. What all can I do to increse gas mileage? I've heard about K&N filters, 180* t-stats, etc. Do they work? Anything else? I plan to use Mobil 1 oil from now on. Should I change the rearend lube also to Mobil 1?

 

3. How do I know if this one has the "trailer towing package"? I have a pick-up I use to pull my racecar trailer, but this would be a nice back-up. There's no hitch on it. There is what loks like a small round plug up behind the rear bumper, but it's not a standard 7-pin trailer plug. Will there be a place to plug in a brake controller under the dash?

 

4. Should I keep the Dex-Cool or change it for green stuff? If I do keep it, how often should I change it?

 

5. Are there any known problems with the '00 models with the 5.3L that I should look for?

 

6. The only thing I noticed strange on the motor is a film of oil on the valve covers around the coil packs. Is something leaking?

 

7. I would like to get a programmer. Any suggestions? Hypertech, Diablo, others?

 

Sorry for the long post. I really do appreciate any help you all can lend. I hope someday to return the favor.

 

Have fun.

budhayes3 Senior Enthusiast

budhayes3

Posted
Posted

Welcome to the forum and the the realm of GM trucks BOP! :thumbs: Let's see if I can answer some of these questions for you.

 

Just so you know: NBS= New Body Style

OBS=Old Body Style

 

1. If you look in the glove box you will find a tag with a bunch of numbers and letters on it, those are you're RPO codes, and they're listed on this site. You should be able to find the info on your rear there. I know that G80 is the the code for locking rear diff.

 

2. I'm not so into gas mileage, more of a performance guy. I love my K&N for this. I'd recommend an air intake, cat-back exhaust, and a good tune (Computer tune that is). PCMforLess is my tuner of choice, Bryan has worked wonders for my truck. The tune can give you both increased performance and mileage There is a link to the PCMforLess website to the left.

 

3. I think the RPO codes will also answer your trailer towing package question.

 

4. You're probably gonna get mixed opinions on this, but I wouldn't change the Dex-Cool. First off, it doesn't mix with the green stuff, it actually becomes acidic and turns into something that resembles cottage cheese, but an uglier color. Any horror stories that you may have heard about Dex-Cool seem to have been resolved, I personally haven't heard of any problems with Dex-Cool in the NBS trucks.

 

5.Known problems: CSK=Cold Start Knock, or Piston Slap, not really a problem, but a "characteristic". The GENIII engines tend to make some noises that may sound bad, but really won't hurt anything. You may notice a knock or tick when cold, and possibly some ticking when warm. The noise you hear for the first few minutes until it warms up is probably piston slap. Due to clearances and the short skirt piston design, the piston actually rocks in the cylinder until the engine warms up and the metals expand. There are some other ticking noises that can be valvetrain, injectors, etc. My 5.3 has been ticking and tapping since day 1 and hasn't lost any performance.

 

The PCV system on these engines tend to suck oil into the induction system. There is a redesigned, fixed orifice style PCV valve that is supposed to help with this, part# 1257217. Less than $5 from the dealer. If you get really into it you can install an oil catch can, but we'll get to that later. (fingers are starting to get tired)

 

6. I haven't experienced any oil leaks, might have some oil slipping past the valve cover gasket bolt grommets, you can always unbolt the coil packs and take a look. (5 10mm bolts secure coil packs, 4 8mm bolts secure valve cover)

 

7. As far as the programmer goes, I feel that you'll get more for your money with a custom tune from PCMforLess. If you really want a handheld, I personally like the Crane/VHP tuner.

 

Hope I was able to help somewhat, I'll let someone else add their thoughts from here! :thumbs:

 

-Billy

mcreyaufmiller Senior Enthusiast

mcreyaufmiller

Posted
Posted

Prestone now has a anti-freeze that is compatable with both green and orange stuff, and guess what color it is? Yellow! The orange stuff is formulated for the alumnium parts in the newer trucks, the green stuff will corode the new metals in the cooling systems. I would stick with either the orange stuff or the yellow stuff. As for changing them, every 50k on my truck. If you cannot find the rear codes in the glove box, look on the drivers door, I think there is a sticker there as well, but not sure. Westers Garage has a mixed reputation, those that use it and like it, love it, those that do not like it, hate it. No inbetween. As for the rest, I agree with Bud!

 

Mike

BOP Racer Enthusiast

BOP Racer

Posted
  • Author
Posted

Thanks for the info you all. That's enough to get me started. Although, if anybody else wants to add more, I'll be happy to listen. I'll also be reviewing old posts looking for more info, and throwing in questions here and there.

 

Like I said, thanks! and I hope to be able to help somebody else someday.

Kgry Enthusiast

Kgry

Posted
Posted

I know GT4 is 3.73 gears and GT5 is 4.10 gears. You mostly likely have one of those two gear sets.

 

A 180 thermo would probably decrease gas milage since your engine wouldn't be running at optimum temp.

BOP Racer Enthusiast

BOP Racer

Posted
  • Author
Posted

Well, I wrote down the RPO's from the glove box and decoded most of them. I have the LM7 engine, 4L60E tranny, and 3.73 gears, I couldn't find my GVW code in the 2000 list, but I did find it in the 2001 list. I have C5W, which is 7000#. I don't have a code for a transmission cooler, but I do have a code for "UY7 - Trailer Wiring Harness".

 

Based on this info, would I be alright to tow a 5500# trailer? I might venture up through Tennessee into Ohio and Kentucky, so there may be some "hills" to climb. I have 2-wheel brakes on my trailer, so I would need to install a brake controller in the Yukon. Is the wiring already under the dash for a brake controller on these trucks?

 

Also, when I change the oil, do I need to reset a "change oil" light or anything?

 

Thanks again.

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