S10 making a quiet grinding noise

I've noticed my S10 makes a noise, and it's hard to notice if you're not paying attention. I don't know how to describe it, but I guess it kind of sounds like a grinding noise. When I am picking up speed, I'll hear the noise for a few seconds, then it quits for a few seconds. Then it starts again. When I hear the noise, I notice a slight decrease in acceleration. It doesn't do it much during dry weather, it's when it is rainy and wet is when it's at its worse. Could this be a problem? Thanks. :)

Of course it can be a problem. Grinding noise is never good

Check your brakes (back first) since they can really be affected by the rain. It's probably just something in there

I could be wrong, but I don't think it's the brakes. They've always worked fine, even in the rain. I think it could be a problem with the gearing. [b]I forgot to add this, but in the rain, I've also noticed that it will shift back into 3rd gear and then back into 4th really quickly, even when I am going downhill at speeds of 55 or above...

I'd still check the back brakes. If there's excessive brake dust built up in there it'll cause them to act funny, especially if its wet. Plus the brakes draging will cause your transmission to think that your climbing up a hill or something, which could explain your downshifts.

Not to mention it's just a 15 min job to check the back brakes, and it might be a free fix