Transmission Problem on 2003 Volvo S40

When I drive my car for a while and I go from going like 40mile and reduce to 10miles then try to go to more miles the transmission jumps or like bucks foward feels like Im being pushed foward.The buck is really hard what should do?Has anyone had this problem with a Volvo S40 2003

Asked by for the 2003 Volvo S40
Make sure the fluid level is OK, and have the software in the transmission control module updated if available.
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I dont have the answer I need the question answered