Okay I have an 88 S4 automatic. I always thought the small cooler up top in front of the radiator was the oil cooler, so I look up the part # in PET 928-307-027-06) in PET and it comes back to "tranny oil cooler". I always thought the two end tanks in the radiator cooled the oil and transmission?? So the drivers side end tank is the oil cooler....what does the passengers side end tank do? I looked it PET, but can't seem to figure it out?

Thanks

 

Brian, as I recall & someone here will surely correct me if I am wrong the passenger side tank houses the trans cooler and this is plumbed into the external cooler at the top/front of the radiator. The driver side tank houses the engine oil cooler.