Ford 1996 Thunderbird Manual page 287

Refill Capacities, Motorcraft Parts,
and Lubricant Specifications
Refill Capacities
NOTE: Rear axle lube quantities must be
replaced every 100,000 miles
(160,000 km) or if the axle has been
submerged in water. Otherwise, the
lube should not be checked or changed
unless a leak is suspected or repair
required.
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