2002 GMC 6.0L

kc5deb · May 4, 2005

It's been nearly a month since I got my 02 GMC 3/4 pickup. It has the 6.0L, which I'm told is rated at 300hp. I'm kinda disappointed, though.

I can't even spin the tires from a stand-still. It has some power, but, it still downshifts on some hills without a load, and just feels "empty" and not at all what I expected from the engine.

Are these 6.0's just overrated, or am I missing something?

I've always heard these engines were pretty stout, but, kinda changing my mind. I mean the new 5.3's are pumping out 300hp now, and kinda giving me an inferiority complex.

Just seems like I should be getting more out of my truck. It seems to have picked up a little power with a 50 series flowmaster, but, just barely noticable; might just be the sound fooling me.

Any hints on waking this thing up without spending 2 arms and leg, or am I stuck with a dog?

SS Crew · May 4, 2005

I had the same problem - I went with the Wester's tune. It made a big difference. It still doesn't have the grunt out of the hole (because the 4L80E trans has a higher 1st gear than the 4L60E trans in the 1/2 ton trucks), but from 2nd gear and on it runs like it should. Check it out.

Westers

snoman · May 4, 2005

It's been nearly a month since I got my 02 GMC 3/4 pickup. It has the 6.0L, which I'm told is rated at 300hp. I'm kinda disappointed, though.

I can't even spin the tires from a stand-still. It has some power, but, it still downshifts on some hills without a load, and just feels "empty" and not at all what I expected from the engine.

Are these 6.0's just overrated, or am I missing something?

I've always heard these engines were pretty stout, but, kinda changing my mind. I mean the new 5.3's are pumping out 300hp now, and kinda giving me an inferiority complex.

Just seems like I should be getting more out of my truck. It seems to have picked up a little power with a 50 series flowmaster, but, just barely noticable; might just be the sound fooling me.

Any hints on waking this thing up without spending 2 arms and leg, or am I stuck with a dog?

<{POST_SNAPBACK}>

HP is "Torque x RPM / 5252" and truck must be gear properly for the load to be able to extract that HP and put it to use. The 6.0 is a good motor but is not a torque monster like the 8.1 is with its greater displacement which pulls taller gearing a tires much better. If you are running near stock tires or bigger with 3.73 axle the preformance will be lacking in that heavy truck as it will also with 4.10 and 33's or bigger tires too. Also you bought it used and it may have had a hard life too. If it has dual exhausts on it with lower restriction mufflers, it will hurt lower speed torque and throttle responce and MPG. More really needs to be know about the configuration of your truck to be able to accurately suggest some possible solution.

kc5deb · May 4, 2005

The truck itself only has 37,000 miles on it (3,000 I've put on there). I know the person who owned the truck previous to me, and they treat their vehicles like gold, so, it's had a sheltered life. As far as the exhaust goes, I haven't lost any noticible power with the new muffler, and I've actually picked up maybe .5-1 mpg, so, I can't see it being the muffler. Honestly, it still runs as good as the day I bought it, but, still doesn't perform like what I think it should.

It's an 2002 GMC Sierra 4x4 2500 ext cab. It does have the tow package with the anti-slip diff, and I believe it has 3.73 gears (not 100% on that).

The lady that owned it before me pulled her 30' 5th wheel camper with it, and she told me that she had no problems pulling it at 75-80mph on long trips, and she said it still had power left. She traded it in since she sold her 5th wheel due to her husbands health, so, it wasn't like she traded it in because it was giving her problems.

That's kinda why I'm guessing SS Crew's suggestion is what is causing my "lack of oomph". Seems it has power, but, holding it back and only using it when it thinks it needs it. When I get the $$$, I'll definatly look into Wester's. Pricy, but, seems like that's gonna be what's going to make it perform. My old 98 ford F150 with the 5.4 seemed to be a little quicker off the line (even quicker than the new F150's) than my 02, but, I can at least tell that this GMC would run circles around my old F150 with a trailer thrown in the mix.

snoman · May 4, 2005

The truck itself only has 37,000 miles on it (3,000 I've put on there). I know the person who owned the truck previous to me, and they treat their vehicles like gold, so, it's had a sheltered life. As far as the exhaust goes, I haven't lost any noticible power with the new muffler, and I've actually picked up maybe .5-1 mpg, so, I can't see it being the muffler. Honestly, it still runs as good as the day I bought it, but, still doesn't perform like what I think it should.

It's an 2002 GMC Sierra 4x4 2500 ext cab. It does have the tow package with the anti-slip diff, and I believe it has 3.73 gears (not 100% on that).

The lady that owned it before me pulled her 30' 5th wheel camper with it, and she told me that she had no problems pulling it at 75-80mph on long trips, and she said it still had power left. She traded it in since she sold her 5th wheel due to her husbands health, so, it wasn't like she traded it in because it was giving her problems.

That's kinda why I'm guessing SS Crew's suggestion is what is causing my "lack of oomph". Seems it has power, but, holding it back and only using it when it thinks it needs it. When I get the $$$, I'll definatly look into Wester's. Pricy, but, seems like that's gonna be what's going to make it perform. My old 98 ford F150 with the 5.4 seemed to be a little quicker off the line (even quicker than the new F150's) than my 02, but, I can at least tell that this GMC would run circles around my old F150 with a trailer thrown in the mix.

<{POST_SNAPBACK}>

Something does not add up because a 6.0 would not pull a 30ft 5th wheel at 75 to 80 mph with 3.73's with plenty of power left! Even with 4.10's that would be a tall order with that engine about the part of plenty of power left. First thing is to look at the option codes and see if there is a GT4 or GT5 listed. Also, if she was pulling a 3o ft 5th at 75 to 80 with 3.73's that trauck has not been babied and was about maxed out while towing especailly on any hill. With a 5th it is not just weight, it is wind drag too.

01silverado2500 · May 5, 2005

I have an 01 6.0L 4x4 with 4:10s and the truck feels like plenty of power to me. You have to remember it has 300hp but it also weighs close to 6000lbs.

ctfan · May 5, 2005

I'm happy with my 01 HD with the 6.0 and 4.10. Like 01silverado said, the truck is heavy. Your not going to win an indy race with it, but you will be able to drag an indy car around all day.

William

kc5deb · May 5, 2005

Double checked; it is a 3.73 (GT4 code) rear end.

Granted I haven't seen the 5th wheel she was pulling, but, I know there are some high profile and low profile 5th wheel campers, and if I had to guess, it was a light weight/low profile 5th wheel.

I too can see that pulling one of the 9000-10,000lb high profile 5th wheel campers would drag it down, and it sure wouldn't have anything left at 75mph.

Also realize, where I live, there aren't too many hills. West Texas is pretty darn flat, and she never really travelled over 150 miles away. There were certain lakes and places they go camping, and they never went much further than that.

I agree that pulling a load at 75mph isn't quite babying it, but, if she had been ragging it to death, it sure wouldn't shift as smooth as it does, and would probably be giving me some troubles by now if she had tore the hell out of it.

She's not one to exaggerate, but, the only real test will be to load it up and see how it runs. Chances are it won't be until late this year if not next year before I get a chance to get an camper, and we'll see how it pulls it then. Maybe by then I'll have a Wester's custom chip, and it'll be a moot point

BTW, it's only a 2500, and not the 2500HD.

Friz · May 5, 2005

I agree with you on the power thing, kc5.

I have a 350 tbi in a cc k3500. I think it will out pull a 6.0 in the same truck. If you look in the heavy duty section, you'll find my comaparison of a '95 cc k3500 5.7 tbi and a '04 cc k3500 with the 6.0.

MrQuadrasteer · May 5, 2005

KC5, there's probably nothing wrong with your truck that a good cpu-tune won't cure. The 6.0 is a great motor, it's just strangled from the factory.

Hey- ours are 300hp, so why do Denali's get 325hp, WITH NO OTHER CHANGES ???

It's all in the tune.

Getchya a Wester's tune. I GUARANTEE you won't be dissatisfied

99Silver6.0 · May 5, 2005

The 6.0 is pretty detuned from the factory. Have a pretty weak spark table. Like they have stated, you need a tune!!!

snoman · May 5, 2005

I have an 01 6.0L 4x4 with 4:10s and the truck feels like plenty of power to me. You have to remember it has 300hp but it also weighs close to 6000lbs.

<{POST_SNAPBACK}>

Not really because you do not tow at 4600 RPM so you do not have 300HP that is really usable and if you tow at 2300 RPM or so you have maybe 120HP availible at most if you are lucky. You have got to get the RPM's up to make the HP.

snoman · May 5, 2005

I'm happy with my 01 HD with the 6.0 and 4.10. Like 01silverado said, the truck is heavy. Your not going to win an indy race with it, but you will be able to drag an indy car around all day.

William

<{POST_SNAPBACK}>

Being how little it weighs (the Indy car) this is no big feat. Heck my wifes 4cyl cherokee with factory 4.10 would probly do it all day with little effort too. (even though the engine is small the gearing and tire size lets you actually utlilize its HP better) The real test is the big heavy high drag loads and a head wind too.

JRKRACE · May 5, 2005

The sluggishness is because of Torque Management. This is a little thing GM puts in the trucks to prevent warranty claims. It's all money to them. As said before, a tuned PCM will take care of the Torque Management along with a lot of other things. I have a PCM from PCM's for Less and it has made a huge difference for me. Granted you are not going to make the truck a dragster, but the smoother drivability and added power is worth every cent.

snoman · May 5, 2005

The sluggishness is because of Torque Management. This is a little thing GM puts in the trucks to prevent warranty claims. It's all money to them. As said before, a tuned PCM will take care of the Torque Management along with a lot of other things. I have a PCM from PCM's for Less and it has made a huge difference for me. Granted you are not going to make the truck a dragster, but the smoother drivability and added power is worth every cent.

<{POST_SNAPBACK}>

Warranty claims may be a factor but one of the main reasons behind it is emmisions control because when you advance or retard engine output quickly it is dirty for a while. It really should be called "power" management. As emissions get tuffer they have to tweak them more and some of those custom tunes blow the emissions right out the window because if it was that easy to get more power and low emissions, they would come that way from the factory.