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MG MGB Technical - Banjo Diff' Oil

Guy's & Gal's.
A simple one this time; Changing the oil in my Diff', Banjo type, early '66. Some "clunk" when lifting off the gas. I have seen/read about Hypoid? Gear oil, CastrolEP /EPI?? etc, seems to be two types of castrol? What do I look for in other brands? Is it rare like 20W50, for old cars only or is it universal common to all? Is it Mineral or Sythetic? I need to know what I'm talking about, otherwise a Pizza faced adolecant will tell me such & such is the canines gonads, just right for my car, (which he probably has never heard of) just to open his till.

B. G. Griffin

midgetComma mineral hypoid EP90 gear oil in both the

B.G., You need EP 90W oil. The EP designation refers to Extreme Pressure. This EP oil will not "squeeze out" from between the contact mating surfaces (gear teeth)making the surfaces go dry thus causing heat and friction. I use a heavier blend EP85/140W in my 79B due to the age and mileage of the car. The diff should hold approx. 1.8 ltrs.


Gary :>{D
79 MGB

The Workshop Manual quotes, for temps above -10C/15F:

Duckhams Hypoid 90 S
Castrol Hypoy B 90
Esso Gear Oil GX 90/140
Mobilube HD 90
BP Hypogear 90 EP
Shell Spirax heavy Duty 90
Texaco Multigear Lubricant EP 90
Fina Pentonic XP 90-140

So Hypoid, EP or HD according to supplier. For temps below that use 80 grade instead of 90 in each case.

Capacity is 2 1/4 Imperial pints, 1.28 litres, 2.75 US pints. The same stuff is used in the steering rack.

Paul Hunt 2

The hypoid gear cut is quieter for final drive use, the trade off is high contact pressure, hence you need EP.
Stan Best

Definitely 'EP'

I've heard bad reports of synthetic oil ion diffs. Having said that, I'm not 100% sure if the synthetics were 'EP' or just straight 90-weight gear oil - or even if they make synthetic EP oil!?

A few years ago, I was struggling to find anywhere selling EP90. I bought some 'Granville' EP90 oil for the race Midget and promptly destroyed two diffs in quick succession.

Luckily, I had a garage full of spares!
Dave O'Neill 2

This thread was discussed between 20/11/2007 and 22/11/2007

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