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I have an 07 Legacy Auto. My mechanic mentioned the transmission fluid was very dark. It's an import, and probably has never been done. A cursory look online (and here) told me to go to a place that did a flush, which my mechanic couldn't do.

I went to a major service/lube chain and paid $300 to "get it done right". I need to sell this car, but to my surprise a couple of weeks later, the buyer's AA inspection pulled up some transmission oil around the the transmission oil pan.

I queried the centre, who took a look (visual inspection), and they said they only touched the lines when they did the flush, and the oil looked "dirty", so must have been there prior to their flush.

I've lost the buyer.

Below are my concerns. I'd like a second opinion on those if possible...

:: Should the centre have visually inspected external transmission parts in a $300 flush? - If the AA could see it why couldn't they?
:: Is "dirty" external oil proof of a pre-existing problem? - I'd have thought any old dust and crud from the road would stick to external oil. It had been ~3 weeks.
:: Why have I had zero oil spots on my driveway, and no other comprehensive WOF or car servicing picked up this so-called pre-existing leak? It's too much of a coincidence.
:: Can a line-based flush result in fresh leaks elsewhere... particularly around the pan? Research online seems to think so. Not that the centre are listening to that argument.

I'm now told I need a new $300 transmission service, where I need to replace the pan gasket. Previously new oil that I paid for in the flush will be lost, making that expensive service largely pointless.

At best they missed the (apparently obvious) leak, worst caused it. I can't afford another $300.

What do I do?

Hi there,
There are two types of transmission service, fluid only flush- suck out and refill using the lines and a special machine. This method is the easiest and the lines used are generally at the radiator at the front of the car. Only one hose is disconnected and it's a long way from the trans pan. It would cost a few hundred dollars and use approx. 8 litres of fluid which is a big part of the cost.
The second is the full pan off, filter replacement service- this is a lot more time consuming and have a higher cost and not carried out often.
A small oil leak around the pan is more of a nuisance and may not be the transmission, it could be the breather plate on the back of the engine inside the area between the transmission and the engine, or other leaks making its way to the lowest point. The best thing to do is to clean it and see where the oil stems from and how fast it returns, which I imagine not very, if you're not dripping oil everywhere. So no it doesn't automatically alert of a transmission issue and road grime loves to stick to oil and make things look a lot worse. The presence of the leak should have been mentioned as a note when obtaining a service just so you are aware and clean it if necessary.

Thanks for the quick response! So can a line-based flush result in fresh leaks elsewhere... particularly around the pan? The work was as you correctly described "fluid only flush".

Not usually, unless they used a cooler hose near the transmission for the flush and it spilt everywhere, but that would be a fresh leak and easy to see. It is common for small leaks to travel around the circumference of the engine sump and transmission pan area as it is generally the lowest point- which gives the appearance that the sump/pan is leaking but until cleaned down hard to confirm.