2001 ford ranger transmission slipping?

Had a old bottle mecron put it in and it drained out the bottom, leaky hose easy fix. The guy at the part store said it takes mecron 5 should I drain out all the fluid 10.5 quarts or can I get by with 1 quart of the old mecron

If the fluid is burnt… Needs a rebuild. Fluid should be red… Not brown. Use recommended ATF only.

Yea no problem with the old fluid. But if transmission is full and still slipping doesn't take much to do internal damage. So you might be looking at a rebuilt transmission. Find local shop at ATRA.COM for more help