Grinding when downshifting

Thanks for all the help fellas!.. You guys are awesome.

Fingers crossed it's just a fluid change to get me back to normal... The guy I bought it from said it had been sitting in his garage for 3 years, so I'm thinking it's possible the fluid just needs a change... hoping anyway.

So GL4 straight 90W or 85-140W... Or Pennzoil Synchromesh.

This Pennzoil Synchromesh stuff, does it come in different weights or is it one weight? I did a quick search online, it said for GM or Chrysler trannys but I couldn't find any different weights.

To elaborate a bit more... the transmission seems to go into Reverse fairly easy from idle. Just doesn't like downshifting at all when I'm driving.