I recently bought a 1994 volvo 940 wagon, has 156k miles, put 4k on the odometer myself. I have no clue when the last time the transmition was flushed if ever.
I guess now is as a good time as any for a flush. My first question is;what type of fluid should I use? A friend told me that if synthetic fluid is ever used, I should continue to used it or risk damage. Is this true? I have no clue what is in it at the moment. Any advice would be appreciated.
The procedure I'll probably be using should be something like below. Have never done aflush before. Wish me luck.

Loosen bolt from bottom of pan. Drain until it stops.
Refill with same amount of fluid
unclip return hose from radiator
Put car into drive and drain 2 quarts (with park brake on :P)
Refil with 2 quarts via dipstick. (located nexto engine oil dipstick)
repeat until clean. It should use about 8? quarts of fluid total

EDIT: And my 2nd question
Recently the service light will come on and stay on for a few miles after I start the car. What does this light usually indicate? How does it compare to a check engine light? does it mean there are new diagnostic codes?

 

I personally would look at the fluid's condition before attempting a change in your garage. There are two schools of thought: If the fluid is super bad, i.e. black and nasty, better not toch it lest the poor tranny is so shocked by the fresh fluid that it stops working altogether. This, although it sounds like an old wives tale, I've seen it happen. The other school of thought is thatchange is always healthy regardless of the condition of the fluid which I am more inclined to support. Then, as much as a do- it-yourselfer as I am, this is one case where if you want athorough job you should get a POWER FLUSH for about a $100... at any oil change place that offers it...

 

Your service light is just a reminder that you need "service". It stays on for 30 secs, then it goes away by itself. Take out the little rubber plug in the instrument panel and press the **** behind it with a little tool, that resets the counter for another I think 5,000 miles.

 

re service light. this light willnot cause any fault codes to log. it is usual preset bya garage when they service your vechicle to remind you when the next service is due. if you do your own servicing ie. engine oil,oil filter ect , then you can ignore the light as long as you keep your own record of when you serviced the car.as tedv points out you can put the light out very easily.