Please Help! Loud knocking grinding noise (anything automotive dummy)
 

Ive had my 99 trail blazer now for almost 2 years and outta no where I started getting this knocking now under the driver side floor board and over the past couple days its gotten worse. Now it progressed to grinding and more frequent if I go over 25mph. Took it for a free inspection (drive and guess) and they said I have to replace my transfer case, 2250.00,:icon_doh: Not possible on unemployment and single mom, any suggestions on possible other less expensive reasons????? Any help right now is greatly appreciated, Ive been car less for 5 days..:icon_cry: Thanks

*Moving from 1st gen Tech to 2nd Gen Tech* - The 1st gens ended in 94...

From the sounds of it, your transfer case likely had a leak which caused the fluid level to drop. The NV236 transfer case that all of the Trailblazer trimmed Blazers came with uses a special fluid and is very sensitive to fluid quality and level. Check your fluid level and probably flush it out. You will need 2 quarts of GM Autotrac 2 fluid to fill it properly. 2 more quarts if you want to flush it again afterwords. If it is making that much noise, it likely is toast.

I have also seen the front driveshaft on these trucks wear out so that is another thing to check.