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BJ8 Differential Oil Change

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AUSMHLY

AUSMHLY

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Haynes service manual says to drain the differential oil every 6000 miles when hot, and fill with 3 pints of Castrol Hypoy (Hypoy or Hypoid?).

Guilty for not keeping up on that.

What brand/weight oil are you using?
 
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It doesn’t have to be hot. Drain it overnight, then fill to overflow plug with your choice of lubricant and enjoy.
 
AUSMHLY said:
Would synthetic oil be better?
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I've used synthetic gear oil in both my Healeys' gearboxes and diffs for many years; Redline MT-90 in the gearboxes/ODs and 75W-90 in the BN2's diff and 75(?)-140 in the BJ8's diff (it has a little whine and the thicker oil muffles it a bit). Yes, it's more expensive but you can certainly extend the change intervals, and I think in the gearboxes it makes shifting a bit smoother and the O/D is a little more responsive when the fluid is hot. I don't use it in the engines because that oil should be changed more often regardless of type,
 
I use Red-Line 75W90 GL-5 Gear Oil in the differential of our BJ7. We have a Toyota 5 speed, and it gets MT-90 74W90 GL-4 Gear Oil. I believe that these are Red-Line's recommendations. I just dropped Red-Line a note, asking for their recommendations as to how frequently to change these fluids on a Healey that is street driven and only for pleasure. I'll advise of anything I learn, and would appreciate other observations regards ol change frequency.
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I've let my gearbox/OD oil go as long as 20K miles. When I drained it into a clean pan there weren't any solid particles and the oil looked, smelled and felt new. There was an extremely fine brass-colored shake in the oil--kinda pretty in the sunlight--but there was no gritty feel whatsoever. Note some greases are oil thickened with soft metal--lithium, moly, etc.--and brass is a soft metal. When I did rebuild the gearbox there was no excessive wear, just the 'usual,' like the ends of the layshaft.
 
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