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The shop manual recommends every 500 miles, but you have to remove
the engine first (/JK--sorta).<br>
<br>
Good question, though. Modern cars--well, 'modern' since about
1980--can supposedly go indefinitely without a diff fluid change
(most have no drain so it's somewhat inconvenient to do so anyway).
I think, with full-syn oil you could go 100K miles or more, even in
a Healey. But, the rear axle housing has a vent and, theoretically,
water could get in and if you try to ford the Mississippi you might
want to check for 'milkshake' (really, I just wanted to see if I
remembered how to spell 'Mississippi'). Realistically, a lot of us
have rear hub seal/bearing and other issues that require a drain
anyway, and trying to re-use oil is a pain so why not install fresh
when this happens. If it's been a long time--or never--since you've
changed it why not do it for peace of mind--and why check for crud
or metal, and replace with a full-syn oil?--then never worry about
it again (unless, of course, ...)<br>
<br>
Bob<br>
<br>
<div class="moz-cite-prefix">On 8/1/2020 7:54 AM, Ron Fine wrote:<br>
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<div>With plenty of time on my hands I am finally getting to
the oil change type of chores on my BN7. </div>
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<div>With the car up on blocks I can get to the things that
need grease and was wondering if there a “rule of thumb” for
when or if to change the oil in the differential?</div>
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<div>Thanks for any suggestions.</div>
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<div>Ron Fine</div>
<div>61 BN7 </div>
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