Cassette jumping

[highside]

Help, after cleaning my bike replacing the chain and cassette (new ones) when i put pressure on the gears jump,they are fine when i pedal normally just seems to jump when i pedal hard.

[nameused]

Possibly the chain is too long? Or the RD cable doesn't have enough tension?

[Bill]

another suggestion ... http://bikeride.com/adjust-rear-derailleur/

and
http://bikeride.com/adjust-front-derailer/