Reply to "Reverse gear - grinding noise"

Sig, some owners have had positive results with Redline diff lube. But it is a thinner fluid with less shock resistence than the recommended (and thicker) 80W90 lube ZF originally specified. If it grinds more- or sooner after warm-up, go back to stock lube. And if all external adjustments don't help, its possible there is enough metal worn away inside the ZF that the shifting will always grind a little, until an overhaul is done. This is, after all a 43-year-old performance sports car and things DO wear out!

Note that if this is whats really needed, all new parts come from RBT Transmissions in Southern California, who bought the design rights from ZF 30 years ago. All other ZF-fixers either buy their parts from RBT or cannibalize other ZFs for useable bits. You can also talk to your local 911 Porsche owners; their transaxles are (I think) built under license from ZF and often have the same problems.