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Oil for Differential


Andrew
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Hello 

Herald 13/60

some advise please.  Just replaced all my seals in the diff, and about to refill with EP 90 gear oil.  The oil that was in is EP 90 GL4 (millers) . Just noticed that the oil I have bought is EP90 GL5 (Carlube) both well known makes but what is the difference between GL4 and GL5. Will it be ok to use in my differential and gear box.

regards

Andrew

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I use GL4 EP80/90 for both as GL5 as I understand it will attack yellow metals, think it is ok for one but not the other.

Sure you will soon get a difinitive answer on here.

http://forum.tssc.org.uk/topic/301-hypoid-oil/?tab=comments#comment-2073

Regards

Paul

Edited by 68vitesse
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The "problem" with SOME but not all GL5 formulations occurs under very high hyboid gear meshing pressures that are NORMAL in a differential - and are NOT normal gear meshing pressures that are present in a gearbox.

The problem is that the active ingredients that give the Extreme Pressure (EP) protection only activate under very high hyboid gear meshing pressures, to create an oil that is corrosive to yellow metals - such as some of the thrust bearing materials used in Triumph differentials. 

It would also damage the gearbox synchro rings if the temperature and  gear meshing pressure conditions in the gearbox were sufficient to activate the chemicals.  Fortunately the conditions within the gearbox are unlikely to activate the chemicals that do the damage.   

Unless one is 100% confident that the GL5 spec oil one is proposing to use in a differential is "Yellow Metal friendly", then it is best to stick to GL4 spec oil in the differential.

For the gearbox, one can usually safely use GL5 spec oil, but its best to keep only one grade of gearbox oil in the garage, so its best to stick to GL4 spec all round to avoid accidents using the wrong oil in the differential.

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Experience of using GL5  in a GL4 Designed diff was a warranty disaster

Witha name chnage over the door they changed the oil spec , it  it wrecked the planet thrust washers

Diffs take a lot of load get very  hot  being the worst case for wromg oils spec

Triumph specified   GL4  so stick with it

Pete

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Hi all

thanks for all the advise. I will pay a visit to the club shop this week to purchase the recommended EP 90 GL 4 oil.  Luckily for me I can pass the shop on my travels.

thank you Once again and happy new year to all

regards

Andrew

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Just looked at the TSSC Shop - there is only 1x choice VFM, Millers 5L EP80W/90 at about £24.60.

Castrol appears to be about £10.20 for 1L.

Regards.

Richard.

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Castrol EP90 GL4 £9 litre, Pennine E80/90 GL4 £4 litre. BOTH available at Club shop. Castrol engine oil 5 litres £27.50, Penine Heritage 20/50 5 litres £14.00. I apologise for my mistake In mentioning Millers but Shop does supply 2 differential/gearbox oils! 

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Hello Gully.

There is nothing wrong with the Pennine option per se.

However when I spoke with the company this morning I tried to establish the difference between their EP and that of Castrol.

I could not pin them down as to the difference and the words "similar" and "almost the same" were used on a regular basis. There is no doubt that Pennine EP does the job BUT I have a question mark over the longevity and the oil shear factor (stability under extreme heat / mechanical pressure which affects an oils viscosity). Any oil has its work cut out and even more so with EP oils.

Castrol EP is mineral based and the company declare that. However Pennine do not state their oil is mineral based on their technical info - saying it's a solvent refined 100% virgin base oil and yet when I spoke with them about that wording they conveyed it is a mineral oil but worded differently. I thought the company would declare their EP is mineral based up front rather than using a different choice of words.

EP oil at £4 per litre is impressive to say the least and yet Castrol charge £9 per litre - I fully accept that Castrol do tend to charge more and over the odds, but a £5 difference is significant.

Under the circumstances and on a personal basis I would feel more comfortable using Castrol, as I say it is purely a personal view and I am not casting doubt on the Pennine product; merely flagging some observations. 

Perhaps I am just being overly cautious.

Regards.

Richard.

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  • 1 month later...

Hi

Started to read this topic, and went Hunting on line, Came up with this, ( The caveat being it was targeted at the US classic Scene and Corvairs in particular) If you are interested, It get boring in places, It does give some idea of the background to the debate GL4 vs GL5.

In essence it would seem that unless you are uprating "your" vehicle substantially, and (or) operating in High Temperature ranges, a (good quality?) GL4 is more than adequate, and will likely be less trouble. One of the worst issues it appears is getting a Spec; and confirming it is complied with?

Pete

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