grinding noise from front end on my '99

[ggsz28]

New member here hoping for some help with my truck. I've got a '99 GMC Jimmy SLT 4WD w/ 102K miles and I've owned it for the past 30K. Whenever I am stopped at a light or stopsign and I take off with anything more than light throttle then there is a horrible grinding sound from under the car/forward part of the car. The grinding lasts for about 1 - 2 seconds. It doesn't do it when I use light throttle but it does every single time when I use say 50% throttle or more. It doesn't matter if the engine is hot or cold. This is the only time it grinds...never at any other speeds. I have some experience with cars but none w/ 4WD. Can someone please tell me what's going on here?
Thanks,
Geoff

[BlazerLT]

Could be a transfer case going out or partially engaged, or a CV joint gone, or even a bearing.

I would definite have this check ASAP at a trustworthy dealer.

[bhesson]

Or an engine mount could be broken. A fast start from a dead stop could cause the motor to torque and the fan to hit the shroud. Check the fan and scroud to see if you see any obvious rubbing marks ...

[ggsz28]

I didn't think about a motor mount. I'll take a look at that in the morning. It's definitely only when the motor is being torqued and it doesn't matter if its in 2WD or 4WD.
-Geoff

[BlazerLT]

How are the CV boots?

Any tears?

[bhesson]

Get a friend to sit in the car and hold the brake while pressing lightly on the accelerator. If the mounts broken, you'll see the engine rise up on the drivers side ...

[BlazerLT]

Could this noise just be a rattling noise and not a grind?

Could be a cat convertor shot.

[rblenkhorn]

How about experience with replacing motor mounts very difficult.. the motor has to be pulled.. ?? My 98 Blazer has a broken driver side. havent been able to really look at it as there doesnt seem to be any room to see anything

[ggsz28]

so I got to hear the noise again this weekend as I drove with my wife to Mammoth Mountain to go skiing. Anyways, I went "off-roading" in 4 Hi and it would make the noise when I give it gas while already moving slowly or when going down a large bump. I'm beginning to think it is suspension related and not a transfer case or motor mount. I haven't got a chance to get under it to take a look yet though. We just had work done on the tie rods and pitman arm about 8K miles ago but it was doing it even before that was done. My wife didn't complain to me about it until after that work was done and the noise was still there. Thanks for the inputs guys.

[BlazerLT]

Honestly, take a look at the cat convertor.

My blazer made that rattling noise also.

It was the internal biscuit inside the cat came loose from the outer metal shell.

Take your truck to a local muffler shop and have them put it up onto a hoist and check it out for you.

[ggsz28]

I really doubt it's a converter. It's more of a scruuuch sound if that makes any sense. It's like the sound of rubbing a rock against the road (like a long crunching sound). Unfortunately I get underway tomorrow morning for almost 2 weeks so I can't look at it until then (I'm in the Navy). I'll keep you posted when I get back and have time to check it out.

[BlazerLT]

Just keep your options open, and check it to just make sure.