Originally Posted by Mike Murrell

Help me understand why you would need a special tool to check tranny fluid on an '89 300E ?

MB maint manual - 1981-1993 has a clear procedure for doing this. No mention is made about using a special tool.

Manny pointed out something worth noting. 80C eng. temp. means nothing.

You can do a cold system check for starters to make sure you are close.
On a cold motor, you would start it up, shift it thru the gears, put it in park, pull stick, clean, reinsert, pull and check. If fuild level is no lower than 10mm below low mark, you're OK.

Now go drive it for about 20 miles. Return and do same check as above, only this time level should be on hot mark.