I wouldn't recommend switching to synthetic. It will probably cause some leaking, and if you're not going to have the car much longer, then just wait until you're ready to get rid of it then change the fluid and filter once again, and hope it helps. You're probably ready for a rebuilt tranny, but if the rest of the car is in good enough shape to justify one, then go ahead and do it. If not, just let it go and tell the prospective buyer about the slippage. My '80 300SD's tranny has been slipping for about four years now (3rd to 4th gear) but I'm not going to put another tranny in it, the body just has too much wear and tear, and I've decided that when that car is no longer serviceable, I'm probably going to pull the interior, which is in absolutely mint condition and the engine as well and junk the rest of it. And if I don't sell my 300E, I'll probably switch over to driving that every day, although I hate to accumulate the miles on it. Anyways, good luck!

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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'85 BMW 745i Turbo