Ebell

So about a month ago I bought this 1986 pickup sr5 ext cab and I wanted to just do kind of a tune-up. So I changed the tranny oil with redline 75w90 and since then its been acting up on me. Everytime i downshift i kind hear/feel a grinding noise through the shifter. I am pretty sure i did it right. All i did was drained it and added oil till it came off the side of the check/fill hole then i capped it off. Im concerned because i never heard the noise before i changed the oil. Any help would be nice.
Thanks