diagnose my noise?

[big JC]

Well, I bought my first safari 3 years ago. A 2000 awd cargo with 180k for $1700. It was banged up but ran perfect and it always exceeded my expectations in mud, snow, and off road. Needless to say I have been hooked ever since. So, I sold said van for $1500 (with 216k), and am now on my forth van in one and half moths. The two after turned into nightmare problems not worth fixing. I now have a fairly nice 2003 awd with 105k, an empty bank account, grey hair, and the beginnings of an ulcer. Here goes , the 2003 starts, runs, and drives perfect. The thing I am paranoid about is it makes a very subtle knocking sound. It ONLY makes this noise (sounds like a faint diesel engine) in first gear at a very specific rpm. Like going up an incline at low speed. As if there is a very specific load rage that makes it knock ( I can not duplicate the noise in park and makes no noise at start up). The noise is hard to hear and only audible with the windows down. It has no noticeable performance problems whatsoever, just the noise. It also has a bit of a rattle around the same rpm but is a completely different noise. It has new auto track 2 fluid, new front and rear syn diff fluid, fresh tranny filter and 5 quarts of syn tranny fluid, fresh oil and filter. I have checked for anything loose or rubbing and all seems OK. The cat (which I suspect and hope over a rod bearing) does not rattle when I pound on it. Thanks to all who have responded to my former posts and at some point I would hope to become a contributing member not in emergency mode.

[Smiliesafari]

For starters I'd check the Knock Sensor. Putting the engine under a load may cause spark knock.

[big JC]

Thanks for the suggestion Smilie. Having read through practically every post on hear at this point, it is clear that you are one of the stronger members. I think I speak for all the less knowledgeable guys looking for help when I say I really appreciate your taking the time to help us out. However, I am confident it is not the knock sensor. With more seat time in the van I would no longer describe the mystery noise as a knock. It's more of a fluttering sound. It seems to becomig from either the trans or tranfer case. It happens from a stand still as I begin to accelerate, just as I begin to load the engine. I can hear it in 2cnd also at low speed again just as it begins to load the engine. If a pull up to a curb with the ebrake on in drive I can duplicate the noise again just as I begin to load the engine. Once the engine is loaded or I give it more gas the noise kinda flutters out and goes away. The noise only happens when the van is warmed up.

[MountainManJoe]

Hi JC. There's a known defect with the balance shaft ...

http://www.gm-trucks.com/forums/index.p ... t&p=345576

[big JC]

Thanks for that forum timelessbeing. After reading it I suspect that is infact my issue. I will contact a dealership tomorrow and had a couple of questions you may be able to anwser. What is the danger of continuing to drive the van with this condition? If it's a defect in the balancer shaft does the gm fix leave the engine comprised in any way? Thanks again!

[MountainManJoe]

Ya got me there. I'm just going to quit while I'm ahead OK