Hey everyone,
I've been noticing a grinding type of sound when i shift my blazer into driver right after starting it. It doesnt seem to make a grinding sound if its warmed up for 5 minutes or so before putting it into drive, but when it's cold and i shift into drive and slowly creep forward there is a grinding sound for about 1 or 2 seconds. As soon as I accelerate and the rev's go over 2K it seems to go away and once I've been driving for a couple minutes the sound will go away.

It seems to only happen when its a coldstart and hasn't had time to warm up, but as i said, once I've been driving around for a minute or two and stop at a four way stop I don't notice any sounds. Does anyone know what this could be? Sounds like its coming from the front end.

Thanks, Mitch

2001 Blazer LS
4.3L V6 Vortec

 

This is interesting. My dad's avalanche does the same thing, and has for the past two years or so. There's a lot of things it could be, but I don't know a lot about these Vortex 4.3 engines so far. Here would be my best guess:

Transfer case for the 4x4 if equipped. My understanding is that these transfer cases spin with the rest of the car in 2wd and engage when 4x4 is turned on. This means that components in the transfer case spin whether or not you are actually in 4x4. Thus, you have a grinding sound because the transfer case (which, in simplistic terms acts somewhat like an automatic transmission), is perhaps loose and needs time to lubricate up after sitting awhile.

The fact is only occurs when moving forward rules out problems with the engine and torque converter, which spin all the time regardless. It does, however, rule in CV axles, transfer case, transmission components, etc. Because it's coming from the forward part of the car, that leaves us with the transfer case and cv axles.

HOWEVER, I wouldn't necessarily rule out simple things like the brakes, either. Brakes can make grinding noises, especially if you have a piston that isn't releasing correctly. Slim chance, but still possible.

 

I was thinking it might have something to do with the transfer case. It wouldn't have anything to do with the brakes tho because if you shift into drive while holding the brake there still seems to be a grinding sound. It sounds like its coming from right by the transmission so I figure there must be something going on with the transfer case. Could this possibly be solved by getting the transfer case flushed and refilled with lubricant at mr.lube or something?

 

This is where my expertise in this area is a little lacking. :P I've rebuilt auto transmissions, but never a transfer case. However, it's entirely possible the oil is old and spent. A fluid change is never a bad idea if you have a lot of miles on the vehicle. However, I would rather do it myself than have someone else do it, simply because you can put in better quality oil than the bulk ordered oil from who-knows-where they use. I would find out how much it is to flush before you decide, and before you do the flush, I would definitely have someone sit next to the car and make sure it is the transfer case. I hate just throwing money at stuff, especially if you don't know it will fix the problem.