My friend has one of these '91 300D 2.5T, I just replaced head gasket for him, blowen on cyl.1. Send turbo out for rebuild and replaced all glow plugs, everything else is all original, 235k miles on the clock still running very strong.

I have a 1991 300D. So far no slippage. Sometimes it may feel like it's slipping if the fuel filters are not changed. You will feel a definite loss of power.

What tranny fluid do you use?

I used Castrol Import Car ATF. Works OK. Now that I have the shifting issues somewhat under control I will next time use Mobil 1 ATF.