An overheated transmission is a timely and costly fix so it's important that your Jeep's auto trans oil cooler hose is working properly. 4WD offers full transmission line kits along with the individual parts needed for installation. How do you know when it's time to replace the auto trans oil cooler hose? A visual inspection may show deteriorating rubber or oil leaking around the fittings of the hose. External signs that the auto trans oil cooler hose needs a replacement is a transmission that is running too hot. If you notice any of these signs, don't put off getting a new hose.