Hey guys, I recently bought a 99 GMC Sierra 2wd Ex Cab w/5.3 and the 4speed auto. It is a very nice truck, and I've already had a lot of fun in it. I basically have two questions for y'all, if you don't mind.

1) My truck already has a flowmaster exhaust (sounds great) and a drop-in K&N along with upgraded plugs/wires. I believe the owner before me may have put a chip in too, since it does seem to have a different powerband than others I've driven and it all but refuses to run on 87 octane. My question is: What else can I do for cheap power?

2) I guess I have a completely open diff, because my tire spins at the first talk of water. What is an affordable solution? I see some factory posi units on Ebay, but are they any good? I don't know if I'd be better off buying a setup from Summit or what...

Thanks guys and in case you're wondering, I posted about my GMC here 'cause there's not much going on in the Sierra forum.

 

Welcome to the forum!!! Here is a universal "free mod" list:

First off, I wanna say that doing these mods on your vehicle will not give you "seat of the pants" performance. They won't"pin your head to the seat", or make you smoke Corvettes. But, neither do the aftermarket alternatives.

Now, with that being said, these mods WILL give you noticeable performance gains, and better fuel mileage. These are mods that I have tried, and I wouldn't recommend them ifI thought they weren't worth doing. They are simple mods that you can do in your driveway in a reasonable amount of time with basic hand tools and common sense. They are for 1999-2007's.


1. "Redneck Ram-Air"- Take your stock airbox out and cut a hole in the front portion (facing the headlight), under the joint where the filter sits. You can do this with an ordinary household drill. BE CAREFULL NOT TO CUT TOO CLOSE TO THE JOINT WHERE THE TOP PORTION OF THE AIRBOX ATTACHES!!! Make sure you clean out all the plastic shavings before reassembly. For best results,I highly recommend a high-flowdrop in air filter such as a K&N. I think Auto Zone sells them for around $50. These air filters are lifetime filters that you only clean when they need to be cleaned. When you go to the track (or around town), you can take the passenger side headlight out and have a free Ram-Air setup. It will help bring cool air in the engine (especially at highway speeds). Money saved-$300 compared to the Vera Ram system. Even more if compared to a ram air hood.

2. "Mass Air Flow Sensor ScreenRemoval"- To do this, you just loosen the clamps around the sensor with a flathead screwdriver, slide the tube to the side and then remove the sensor from the airbox. CAREFULLY unclip and remove theconnection. With the sensor screen side down, VERY CAREFULLY push the screen out with the end of something (Craftsman ratchet handle works well), MAKE SUE YOU DO NOT HIT THE SENSOR WIRES!!! Put it back together and be sure to securely fasten the connection and air tube. Money saved- $300-compared to an aftermarket MAF sensor.

3. "Air Gap Manifold"- Locatedunderneath the throttle body,under the intake manifold and above the lifter valley,there is a little insulating pad that helps cold starting and warmup. In environments were this is not needed, it can be removed, it's your decision. Just unhook your intake hose from the throttle body, move it up and out of the way, and you'll see it. On the back side of your engine, there is another one. Just climb up there, reach around, and pull it out. This one won't come out as easily, but it's still not too hard. Next, remove your engine cover from the top of your engine. There is about 3/8" of insulation on the underside that is good for cold weather, but that's it. These can comeoff andgo backon andgo in and outany time you want.The cover has a bolt on the top and little clips on the back. Money saved- N/A, to the best of my knowledge, nobody makes an Air Gap manifold for the LS1 series engine.

4. "Throttle Body Coolant Bypass"- On the bottom side of your throttle body, there are two hoses. These hoses bring hot coolant through your throttle body and like the pads, assist in cold weather startup. Do you realize how much better your truck runs when it's cold, (temp gauge at or below 160)? When it gets warmed up, (gauge at 205-210), throttle resonse is greatly reduced. This mod wiil let you have that throttle res

 

Also, what does your temp gauge read??? If it reads right around 210 degrees, you might want to get a 160 degree thermostat. It is a great way to get some extra power out of it without spending a lot of $$$. Headers are also a great bolt-on modification... Longtubes with a ceramic coating will give you the biggest incrase in power. Throttle body spacers also increase throttle response slightly, and mine gave me about a mile per gallon on the highway... Royal Purple fluids are also a great way to get a few more ponies to the ground. They are also the best product out there when it comes to lubricant for your vehicle.

As far as the rear-end goes, I would look around and see what is out there, and base your decision on what you intend to use the truck for...

 

Wow, I bet if I do all of those at the same time, I'll notice it, though I probably won't be able to do them all today. I definitely will do the screen today, though.I'll leave the exhaust alone, since I already have the flowmaster setup. As for the temp, yeah I do run about 210, where can I get a low temp thermostat? That also sounds like something I'd want to do.

On the rear end, I mainly want something that will help me out when I'm pulling my boat. As it is now, traction is just pathetic and will only get worse as I add power. I'm not planning on any serious off-roading, but it would be nice if I could handle some light mud. Are the factory lockers any good? Thanks again buddy.

 

You can get the thermostat from Summit or Jegs for about $50. It is the same on on the LS1's, but it is the one that includes the housing...the expensive one.

As far as the traction issue, check out the G80.

 

$50 for a thermostat!!! goto your local napa or oreilys auto parts and pick up a 180 degree for around $15. The 160 is too low anyway, but they will have it for about the same price too.

 

Hey by the way I did get that screen out. I think it's a little peppier now. I'm going to do the coolant bypass next, there's no reason for me to have it in Alabama.

 

I would invest in the throttle body spacer. It truley and honestly boosted my trucks mpg by 2 and that's the only mod I have. I'm getting 16 mpg highway which is really good for a 2500 4x4 with 150k+!!! I got the transdapt from summit and it was only $50. Hunt4game got his at the same time and he really likes his....
Just my thoughts.

 

No, the 99-02 LS based truck engines take the thermostat that includes the housing....and 160 degrees is no too low.I've got one on mine and it runs much better. Ask anyone that has one.

 

180 degree thermostat with housing from autozone is 31 dollars. so between what yall said. 160 was the same price, but they were on backorder, so i just got a 180.