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Silvertwinkie · 07-22-2004, 06:17 PM

Ok, I know we've talked about this before. However, I was under the impression that GM fixed this issue for the 2004 models. The one where for the first 20-30 seconds of startup, the engine has a slight knock to it.

I found a new 2004 3/4 ton Suburban today with the 4L80E and 8.1 and sure as all hell, the thing did the piston slap (knocking sound) for about 20 seconds after it was started.

Anyone else have an 2004 8.1L? Does it too have the knocking sound from what sounds like the piston slap?

Also, just to verify, those of you that do have the 8.1L are you getting about 10mpg all around (towing, city, hwy, etc)?

Thanks.

Eric

john hd · 07-22-2004, 06:51 PM

eric

new new or slightly used?

what kind of oil filter is in it? was it sitting for an extended period before starting it?

john

Silvertwinkie · 07-22-2004, 07:00 PM

19 miles like new new.

Not sure how long it sat, but I ran it for about 5 minutes got warm, not hot in the 85 degree amb outdoor temps. Turned the key off, let it sit for about 5-10 minutes and she did it again.

It had whatever the standard PF GM oil filter came installed from the factory.

davidz71 · 07-22-2004, 07:46 PM

2001 8.1 in a 2500hd with no knock. I get 14.9-15.1 on highway, no A/C and 68 mph. In town with A/C I get either side of 10 mpg. Towing at 65 mph I get 11 with A/C and 12 without. I also have the 3.73 rear end.

Silvertwinkie · 07-22-2004, 07:49 PM

David,

You burnin any oil?

Thanks for the info you shared.

Eric

john hd · 07-22-2004, 08:17 PM

eric

have the dealer let you take it "on approval" for a couple of days and see if the noise quits or gets worse. or the deal's off!

otherwise, walk away!

btw, is a mexico truck?

john

Ken J · 07-22-2004, 08:24 PM

Eric

I have the 8.1 in my 2002 Avalanche and love it. A really sweet running machine. Yes it uses as a quart of oil between oil changes - have to remember those pistons are about the size of milk jugs - oil use is expected. Get up to 16-17 miles to the gallon on the highway, 10 mpg towing 25 Tradewind and 12 mpg towing my old 59 Traveler.

Had the front end aligned the other day, had a hard time getting it back from my mechanic after he drove it

I don't get any knock at startup, its been a little chattery until everything gets going. Again, don't forget its a BIG motor.

Ken

Silvertwinkie · 07-22-2004, 09:19 PM

That's a good queston John. Not sure where it is assmb, but I seem to recall some place in the US.

Ken, thanks for the info....you know, we owned a 454 7.4L in 1985. It towed most of it's life a 24' SOB. The truck in 1998 had 135k on it and it too was a big engine. It never burned any oil between changes-- never, not once. The 8.1L is a 496. To me I agree it's a great engine, but I think a quart between oil changes is a bit much considering what I've seen out there first hand.

I think I am just gonna walk. It is a nice truck though.

71_safari · 07-22-2004, 10:01 PM

I think if it is already making noise it is best to steer clear. Doubtful it will get better. I can't believe that GM hasn't completely fixed it yet. They said it was fixed in '03, then '04, and yet at the same time they also claim it won't hurt longevity. Uh-huh. I recently heard a new one start up from 10 ft away and it clattered pretty bad. Noises like that worry me too much. When I had to get a new truck this Spring I seriously looked at the new 2500hd, since my last truck was a K2500, but I just knew how bummed I would be if I got a bad one, so I decided not to chance it. Its a shame because the GM trucks drive really well and the 6.0 is an awesome motor if you get a good one, which I'm sure most are. My luck though, would be to get one with a problem.

The old 5.7 was so incredibly reliable. What happened?

john

jordandvm · 07-22-2004, 11:55 PM

My 2004 4x4 2500 8.1 with 4.1 axle Avalanche is a little chattery on startup like Ken's and then quiets down, but no knocking. I hear the chatter probably more since I park in my garage with the echo on the walls. Gets about 12mpg city/hwy, 14 highway, 10 pulling my 22' CCD. Great tow vehicle!

john hd · 07-23-2004, 04:50 AM

eric

one other point, ask the dealer to change the oil then start the truck up again.

they may have 0w30 in it from the factory!

i'd still walk on this one! good thing you didn't order one to hear it clatter on startup!

john

Silvertwinkie · 07-23-2004, 06:08 AM

Yea, I also reviewed the www.pistonslap.com website. It appears that the new pistons that were discussed for the 02 model year may not have appeared as once thought. I could live with a bit of knock at startup as it was slight, but as indicated, it might get worse if it is already doing it at 19 miles on the odo. Plus some of the oil consumption comments also have me perplexed. I mean an engine that is still fairly new (IMHO) not be chewing up a quart of oil between oil changes. Maybe I'm just out if touch. None of the cars my fam or I have ever owned 305s, 307s, 350s, 400s (a few 60s 400+s), 454s have ever chewed any oil in their life, or at least that was noticeable on the dipstick.

I suppose if I wanted the piston slap sound, I'd get a Duramax, which frankly, I still might do since the same gassers that are placed in the 3/4 Burban, go into the Silverados as well.

Anyone own a Duramax that drinks oil?

59toaster · 07-23-2004, 07:21 AM

Put a A/C filter on it.

Most start up knock is due to crap anti drain back valve in the filters. Amoung the worst are FRAM and anything you get a oil change place. Stick with a A/C filter and you will be ok. Bosch filters are made by the same manufacture as A/C and I have had good luck with them as well.

My 88 Burb was doing this when I bought it. Change the oil and got rid of the fram that was on it and it has to sit for several days now before it will do it at all.

A good read.
http://minimopar.knizefamily.net/oilfilterstudy.html

Silvertwinkie · 07-23-2004, 08:32 AM

THe PF-XX filter I was talking about was the AC Delco brand, I was just calling it the model number PF-??

Anyway, all trucks that I heard the rattle on startup had AC Delco filters.

59toaster · 07-23-2004, 09:24 AM

Wow! My 454 with 84k on it has to st for days for it to happen. Now my Yota is a rattler but at 195,000 miles I'm not real upset about it.

raebaker06 · 07-23-2004, 09:48 AM

If you hear noises ,and it makes you nervous ....don't buy it. It will only get worse, ..but then maybe you like to spend money. I have been driving and towing since 1950 and when after many years and miles it starts that noise I sell it before it becomes obvious.
The only engines that I know that click and clatter at start up are Rolls Royce Merlins.
But they are not for the average guy.They start at 2500 HP

Rae

Silvertwinkie · 07-23-2004, 03:11 PM

Talked with the dealer I bought my SS from. Really nice guy, no BS or anything like that. I asked him about the piston slap issue. Told me that there have been issues, but nothing that he has seen first hand. I then got the standard GM company line about some knock won't hurt, etc, blah, blah, blah, then I asked him to look at Duramax/Allision crew cabs.

I like the 6.0L and also like the 8.1L, but to be honest, between what has been posted on this forum, www.pistonslap.com and the dealer ack that there have been issues, is enough to keep me away from plunking down $40k on a truck that **might** develop issues sooner or later. I guess I kind of look at it this way, if someone told me that a certain type of boat had issues, might be fine, but could have issues, would I get on board for a Lake Michigan boat ride? I also understand that there might be a whole bunch of emotions and amplified issues that increase the hype to the piston slap issue, however, as one person pointed out, with my luck, I'd prob get the clunker that had the issue and it would really upset me (moreso than any QC issues I've had with my 'stream).

Do I want to take that $40k chance?

I'd be really interested in hearing if any of you Duramax folks have had any issues, particularly when it comes to oil consumption. Maybe I'll start a different thread though.

Ken J · 07-23-2004, 06:33 PM

Eric

Perhaps it the thin air at this altitude - have had several vehicles that use a bit of oil between changes

Anyway, I understand your decision - seems that buying a GM product is a 50/50 deal these days. I have a good friend who has had several Surburbans - this last one - 2003 is nothing but trouble for him - piston slap and has had electic problems too - like had to be towed once because it would not start - something to do with a defective security system. So he's gonna buy one of those new 4 door Toyota pickups.

One of the reasons I went ahead and bought a GM product is because I got a screaming deal on it $5,000 below invoice (yes you heard right) and I guess I lucked out, because I REALLY like the truck.

Ken

Silvertwinkie · 07-23-2004, 10:54 PM

Ken,

If it works for you that is great. Alt could have something to do with it.

I am very happy to hear when folks are pleased with a fairly large purchase. You hit the nail right on the head. 50/50. That seems like a hell of a chance given the cost...and that's not easy to ack given what a GM advocate I am. Now I know Airstreams have issues, but they have a better hit rate than 50/50 on the main components.

The whole thing that got me started on finally looking at a truck, was the accident I saw on my way home from Mackinaw and my displeasure of how my current rig handled when higher winds were around. Plus going up hills on the hwy really takes it's toll. I mean if I was going 65, I'd drop down to 50 so that I wouldn't have to downshift all the time (which is what tow/haul helps with).

At any rate, now that I am serious about looking into a new truck, I seem to keep peeling layer upon layer of stuff with the gassers GM has out. Guess this is what folks call doing homework. Funny thing is that the Duramax diesel folks have darn close to a 95% satisfaction rate. I even posted a thread here asking folks that I know will tow and their info was very positive as well, as was most of the info on thedieselplace website.

The diesel does come at a premium, but if I can get an '04 with all these discounts they are offering...seems like a good idea...if I can find one.

Eric

overlander63 · 07-24-2004, 07:23 AM

Quote:

Originally Posted by 71_safari

The old 5.7 was so incredibly reliable. What happened?

john

GM seems to be sacrificing tolerances for better MPG, for the CAFE standards. The more metal they can take out of the engine, and the more of the engine they can make out of aluminum the better mpg it gets,because it weighs less. Unfortunately some of them sound like a coffee grinder with a broken gear. A friend bought a brand new Tahoe, had the same issues with noise. His noise did go away after about 10,000 miles, but I would not have been so patient with it. And I don't know if the noise will come back, pretty bad for something that costs anywhere from $20-40,000 depending on what vehicle it is in. For that amount, I want it to serve me drinks, and drive itself down the road. Silently.
Terry