recently the heat wave has put a pounding on my c220 and after the last day of 100 degree weather a new problem has shown it's ugly head, I'm getting a clunk in my shifting like a bad U-Joint but I believe it's a result of old tranny fluid as it is old brownish and has a burnt smell as well it appears to be a quart down so I am hopeful that a flush of the system will solve this problem. My problem is I've been unable to find a guild on flushing the tranny and on how much fluid I will need to refill.
So if someone could give me a guild to doing this my self I would be greatly appreciated.

I have a 1995 C220 and it has a small torx on a small corner of the tranny pan. after I let it bleed I took off the pan cleaned it and removed old gasket. put it back with new filter. I bought 7 qts because autozone said it took this much. It only took about three quarts. i added too much and it started leaking out the overflow hole. lesson learned pour little by little and keep measuring