Bucket truck issue

[ClintCantrell]

Hi all. Im new to arboristsite. But here goes- I've been having an issue with my bucket truck. Everything works fine except the lower boom going up. I have to have someone give my truck some throttle to get the lower boom up. Once its about halfway up it works fine. And by throttle I only mean about 200 RPM. Someone suggested this could just be a filter and fluid change. Any ideas? Thanks in advance.