The trans in my red 1988 260E failed. But the drivetrain in that 260E is from an 88 300E. So really it is a 300E trans that failed. I estimate that the trans had 200k on it when it failed so I'm not complaining.
Based on the overall condition of the donor car I can tell that it was ridden hard and put up wet so the whole thing was a crapshoot. I had changed the filter and fluid at the time I put the 300E drivetrain in my 260. I used Febi fluid at tht time. I wouldn't use the Febi fluid again simply due to cost. I didn't know better then but I do now.
I intend to use the Valvoline Maxlife fluid in my car at the next change and I'll be using the Dexron version unless I learn otherwise by the time I do the job.