Castrol Syngear 75W90

[Tonto]

Hello all. New to the group and have a technical question regarding Castrol Syngear. Does this gear oil have a limited slip additive in it already? I'm working on a 2007 Mazda B3000 that actually calls for 80W90 but living in Canada, 75W90 always seems to be preferred over 80W. The problem with the rear differential is there is minor chattering when accelerating. The fluid service was done in late October and my co-worker is just now telling me about this noise that he says started right after the fluid service. We're not sure if we need to add a LSD additive or not.

TIA,

Kirk

 

[BeanCounter]

What does the manufacturer of the limited slip or Mazda say about the necessary fluid requirements, first of all?

I don't think Syntec gear oil has limited slip additive in it, although it says it exceeds the GL-5 requirement for limited slips, etc.

 

[LoneRanger]

If you're referring to Castrol Syntec synthetic gear oil, here is the response I received from Castrol when asking a similar question:

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Thank you for contacting Castrol North America,

Castrol Syntec Gear oil SAE 75w-90 exceeds the service fill requirements of conventional and limited slip differentials therefore it does contain friction modifier.

Please contact Subaru for further assistance.


Castrol Consumer Relations

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CONTACTREASON : Inquiry
INQUIRYDETAILS : Subaru specifies 75W90 GL-5 gear oil to be used in
the manual transmission. But can't use gear oil w/ Limited Slip friction modifiers.

My question is: Does the Syntec GL5 Synthetic Gear Oil contain Limited Slip friction modifiers? If yes I can't use it in manual transmission, if no then I can.
CARMAKE : Subaru
CARMODEL : Forester 2.5X AWD
CARYEAR : 2009
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[Tonto]

Right from the Motor lubrication recommendation guide:

1998-2008 Ford Ranger
1998-2008 Mazda B2300, B2500, B3000, B4000
Differential:
Rear: All W/O FX4........... 80W90 GL-5 (footnote 1) [Add 4 oz. friction modifier meeting Ford spec. EST-M2C118-A for complete refill of Traction-Lok axles]
All W/ FX4..........Synthetic 75W140 GL-5* (footnote 1) [Add 4 oz. friction modifier meeting Ford spec. EST-M2C118-A for complete refill of Traction-Lok axles]