After picking up the new Jayco outback Expanda and heading off up to Moonta last weekend we had the same problem with our previous SR when towinig would either have the A/T light come on up hills or in sand or it would spit out of the breather and spray back underneath the car.
We did no hills or sand just flat roads and towing around 90-100km/h and when I felt the need would slip it into overdrive and I think this is were it had a little spit as when we got home the evidence was under the SR5 no light though.
So off to the local trans guy and he said around $350-$450 depending on mounting, I said I reckon I could give it a go myself so he sent me to his wholesaler to get the biggest one I could fit, so I got one for $120 plus $20 for some extra hose didn't want to start the job and be short of hose and as it turned I needed it.
The size I got was 255mmx280mm running through the car radiator first then through the second cooler, all up took a few hours to fit , I also moved the horns to the side and tidied up the messy wiring after toyota did the indicator up grade to increase the air flow.
We are off again for the weekend so will let you know when we get back to see how it goes with higher temos in SA this weekend.
There is also enough room to fit another the other side if needed.
Christian