Automatic Transmission Sluggish

[Capp]

Hi Everyone,
Hopefully someone has had this issue in the past and can assist me with a resolution. I own a W215 CL500 2001 model and have an issue with the automatic transmission. The car drives well and gear changes are smooth, however when I accelerate or touch the throttle the engine revs increase by about 300 rpm without the car speed increasing. There is no slip and if I drive hard it responds well. Previously the transmission did not behave like this, it is best described as the torque converter slipping slightly.
Thanks in advance for your replies.

 

[AMGeed]

Have you had the ATF levels checked, or changed the fluid at all?
Might be your first job. A fluid change is around £160 at an indy

 

[Capp]

No, I was thinking of changing the filter and flushing the oil, but suspect there is more wrong that this so I was looking for a fault that I could maybe rectify while I've got it stripped.

 

[whitenemesis]

Get the car on STAR and see if any codes stored. If it's more than low atf there will be error codes.