I disagree. The DeTomaso Forum is full of unmolested-car owners that first discovered their ring gear bolts were a problem when a bolt-head appeared in their ZF drain oil! One owner bought a low-mileage car in Arizona last year and was detailing his engine compartment. He had removed the ZF to have it polished and an attack of guilt made him open up the lower cover for a look. ALL TEN BOLTS WERE BROKEN! The ring gear was wobbling around on the bolt shoulders and the bolt heads had been rattling around in there so long, they were round, not hexagonal..... I watched Wilkinson sell a guy a spare lower cover for a ZF 10 yrs ago at 'Vegas, when just after arriving from LA, the owner put his ZF in reverse to change parking spaces, and a broken bolt-head caught in the gear mesh and was spat out hard enough to break the lower cover. A gallon of hot 90-wt covers a very large area of the average parking lot.....True, not ALL ring-gear bolts will loosen or break. But to me, the risk of destroying a $6000 transaxle is matched by changing 10 known-to-often-be-defective Euro-bolts to cheaper but stronger US-made ones, and safety-wiring them correctly is simple insurance. Your choice-