[Healeys] SAE 140 Use In Differential To Reduce Noise?

Bob Spidell bspidell at comcast.net
Wed Dec 23 21:54:26 MST 2015

Thanks for the detailed feedback Graham.   FWIW, there's been a 
discussion on this topic on the Forum.  There's at least some agreement 
that the 3.45 diffs may be a bit noisier than the 3.91s, even when set 
up by a qualified shop (it seems to be hit-or-miss). Noisy diffs have 
been a problem for many years; when my dad was a service rep at Ford 
they got lots of complaints about noisy diffs in early Mustangs.  My 
2008 Mustang has a noisy diff--how's that for respecting heritage?

I still have the 3.91 that came out of my BJ8 at about 120K miles. The 
wear pattern was barely discernible but flawless.  It made no noise that 
I ever noticed.  I suspect the only advantage to a heavier fluid is that 
it muffles the noise a bit more.

Merry Christmas to all.


On 12/23/2015 7:47 PM, Graham Wilkie wrote:
> Hi Doug,
> I received several responses; the conventional wisdom was to remove 
> the differential and have a specialist carry out the work. That is 
> on my to-do list.
> Until I get to that item on my list, here is what I have done. I 
> drained the Penrite 80W 90 mineral gear oil, and replaced it with 
> Penrite 140 Gear Oil - Premium Mineral. This product claims "for 
> quieting noisy differentials, where the noise is due to wear, thus 
> prolonging the life of the unit".
> After about 60 miles of driving, the whine was certainly still 
> evident. A bit quieter, but not significantly so. Following 
> suggestions from others, I then added Nulon G70 to the Penrite 140 
> Gear Oil in the differential.
> I have covered some 1,123 miles since then.
> *Conclusion:* The pitch level of the diff whine is lower, more like a 
> humming; it is now easier to live with at and above 60mph. The most 
> improvement occurred after adding the Nulon G70. I will continue to 
> run this combination in the differential for now. Knowing the result, 
> I would do it again.
> As has been pointed out by others, the real fix is to have the 
> differential adjusted or repaired by a differential specialist.
> Hope that answers your question.
> Regards, Graham Wilkie.
> Moruya, Australia.

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