chevy blazer s10 makes noise while driving

I just bought a 91 chevy blazer.After driving it for a while it starts making a lawnmower type sound coming from the right wheel area.When we take the 4x4 shifter from 2 wheel to almost 4wheel the noise starts going away.Then we put it back on 2 low and the noise goes away for a little while then the noise comes back.Someone told me it could be the transfer case or the front differential.Has any one else had that problem?Please I'm tired of spending money on guessing games.Thank u to any one that can help.

Have you checked your front differential fluid?

Have you checked you transfer case fluid level?

Sounds to me like the vacuum pulloff switch for the engaging of the 4WD. I had this happen on my 1991 Blazer. The valve leakes and sends vacuum to the pulloff and attempts to partially engage when not asked to. Check the vacuum switch to see if it holds a vacuum. A new one is around $30. It is located on the transfer case with 3 vacuum lines running to it. This is a very common part to go. Also check all of the vacuum lines in this series to see none have leaks. Some are routed near the exhaust and the lines can get old, dry and cracked. If you need more info email me at strynar.mark@epa.gov. I can give you more info. Good luck.

Thank u blazertand mjs22.We checked the fuild for the front differential and it was bone dry.We added fuild yesterday but it is still making noise.I will check the transfer case fuild and the vacumm pulloff switch.I appreciate your help and I will let u know how it goes.Thanks again!

Thank u blazertand mjs22.We checked the fuild for the front differential and it was bone dry.We added fuild yesterday but it is still making noise.I will check the transfer case fuild and the vacumm pulloff switch.I appreciate your help and I will let u know how it goes.Thanks again!

I hope you used the proper gear oil.