4 speeder rooted i think? could it be...

i was driving my ea recently and i've noticed the gears slip in all four gears. but really strong on 1st, 2nd is ok, struggle to change in 3rd, and 4th abit weak when i applie more throttle on it but then it jumps back into 3rd

well thinkin i needed to service my box so then then i did. filled in 5L of TQ95, new seal and filter then took it for a test drive 1st is ok, wont go to any gear unless i release the pedal by and inch and gettin into 4th is very shocking.. very disappointed
what other problems could it be?


thanks guys