Have just disposed of this car in favour of a new Honda CRV. This is as a result of similar problems. Since 2004 when I purchased for $A57,490 3 electric windows failed $471.00 each, climate control fan speed regulator $846.00, 4 new engine mounts $284.00, 3 various oil seals including rocker cover $521.00 and automatic transmission work $3650.00 plus labour for all the above listed items totaling about $2800.00. This was all on a dealer serviced car from new, I bought it at 107,000km December 2004 sold it March 2007 at 144,000km for $22,000 trade in. NEVER AGAIN!
I had the same problem with my gear box at 110,000km, had to be completely rebuilt at a cost of $8,000AUD, the Mercedes Dealer had serviced it from new and said it was quite normal for a gearbox to go at 100,000km. I have never had a gearbox go on any car I have owned and they had done a lot more than 100,000km. I also have a 1990 300E with 170,000km and a 240D with 350,000km both still on the original gearbox?? The 5 speed auto feels fantastic and is silky smooth through gear changes even at red line, but is just too weak.
If the fluid/filter changes are performed at the specified intervals, the gearbox will last much longer than this.
Agree about the transmission fluid, should be regularly changed. Every 50M-75M. MBZ toted this as a maintenance free box, but as many of you know, this not the case (pun intended).
Anyone in the market for a used E class, nowadays, will be hard pressed to find one not exceeding 100M. So, maintenance info is always a plus. Also, E320 transmissions (remanufactured) on the Internet can be found fairly priced since, these cars sold very well, and even today, parts are very abundant.
Also, check out MBZ enthusiast forums. I found many friendly and experienced fans, that have been very helpful.
I love my E320. And the MBZ community is awesome. All that being said, however, the Japanese do make a damn fine car. And used German vs. used Japanese, I would have to go Japanese. I think your dollar goes farther, but not funner.
PS. A good thing about buying a used Benz is at least you know what will break/fail. All the negative posts are for the same problems.