[Healeys] Diff oil

[Bob Spidell]

Hi Peter,

I've had my BJ8 diff apart a couple times ... didn't see anything resembling brass in the pumpkin or the axle bearings.

The (potential) problem with some gear oils--i.e. GL-5--are the 'Extreme Pressure' ('EP') additives necessary to combat 
the shear forces in a hypoid gearset.   The EP additives--usually sulfur-based--supposedly will chemically attack brass 
components.

Bob


On 7/13/2012 7:20 AM, Peter Caldwell wrote:
> A further question on this topic.   Some older British vehicles had some brass parts in the diffs. I have heard there 
> is a problem using a GL-5 specification for those applications. The current Castrol Hypoy C is GL-5.  I know that 
> Redline makes a GL4 spec gear oil. Is brass or bronze content a consideration in Healey differentials?
>         Peter C
> -- 
> At 02:05 PM 7/12/2012, Bob Spidell wrote:
>> Everything I've seen/read/heard indicates you shouldn't mix oils of differing viscosities, esp. multi-vis oils. The 
>> multi-vis oils are a blend of base stock--e.g. 10W-40 has a base stock vis of 8 (I think)--and various 'viscosity 
>> improvers' or VIs. The VIs are polymers that start out as straight chains then sort of 'coil up' as they get hot to 
>> thicken the base stock beyond what it would otherwise be at a given temperature. I don't believe the effect is 
>> linear--i.e. mixing 80W-90 and 85W-140 won't give a blend proportional to the mixed quantities. Some say you 
>> shouldn't even mix different brands of same viscosity, but I personally wouldn't lose too much sleep over that. As an 
>> aside, you can mix grades of gasoline to get differing octane ratings; in fact, I believe most gas stations have just 
>> two tanks from which a third blend can be mixed at the pumps.
>>
>> I don't think 85W-140 would hurt a Healey diff--it may even be recommended in the manual, haven't looked in a 
>> while--it'll likely be a similar base stock to 80W-90 with tons of VIs. The problem is the VIs chains shear over time 
>> and the higher vis number goes down.
>>
>> Bob
>
>


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Bob Spidell           San Jose, CA            bspidell at comcast.net

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