Hello

Hoping someone can help. I've been driving an 04 Spacegear gas with A/T. When I switch on the overdrive, I hear a fast clicking noise inside the right side of the dash behind the glove box. It sounds like a relay switching rapidly. This only happens when the overdrive is on and does not happen when turned off.

Is there a relay for the overdrive? Do I need to have this checked?

TIA