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Differential oil and lesson learnt.


The Pikey

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Over the last 2-3 years I have suffered from OCD regarding the Sierra diffs that are in our 7’s. I could not understand why some were quiet and some were not. OK there are poorly set up ones out there and these will obviously be carp but even ones set-up right could sound whiney or knock.

 

I reconditioned the diff for a Caterham I have just completed and was chuffed to death when it was almost silent with no knocks or whines. The diff had the correct oil in which was old stock Ford branded 90 single grade. I also added friction modifier for the Titan LSD. Then after 160 miles to run the engine in I put the car on a rolling road for a day. Afterwards the diff had transformed into a whining grinding, knocking nasty thing. So later that week and convinced I had knackered the diff I took it out the car. I was expecting to see bearings knackered, pre loads lost or a chewed up pinion. But it was perfect, the backlash was within 3/4 of a thou of where I set it and the pinion and bearings looked perfect, so what had changed?

 

I spoke to Phil at Road and Race and he said there was a chance the molecules in the oil had been squashed and the oil had passed it’s useable state. I was a little sceptical about this but as he’s the expert on these things I took it on board.

 

Anyway, I put the diff back in the car. This time I decided to try a Motul semi synthetic 80w140 diff oil, it sounded worse than it did after the rolling road session. Not only did it whine and grind on over run but it clonked like hell as the plates released to the point where I thought I had made some mistake fitting the diff back in back in! I then drained the 80w140 out and as an experiment and to make sure all the 80w140 was out I filled it with the Caterham diff oil I had left over from a previous build. This was better, the LSD plates creaked on turn (no friction modifier added) but nothing like with the 80w140 but there was whines and grinding on over run. I then drained that out and while waiting for some more old stock Ford 90 grade oil to arrive I filled it with some Castrol B373 I had on the shelf, this is mineral based 90 grade oil which is supposed to be good with LSD’s. With the B373 there was no LSD clunking so it’s obviously ok for use without friction modifiers but there was a faint whine and a very slight grind on over run. So the B373 is better than the Caterham stuff but the diff was still not as quiet as it was using the Ford 90 grade oil before the rolling road session.

 

Then yesterday I drained out the B373 and filled it with the 90 grade Ford old stock stuff that had since turned up and although as it was wet I only went on a short drive it was clear it was back to being almost silent again.

 

I’m really glad I did these back to back tests and I’m now convinced that the type and brand of oil we use in these diffs is more important than we think. I also think that if you have a high powered car and you have a noisy diff then you may have oil that’s past it’s best and you might be pleasantly surprised if you changed it

 

The Ford part number for the 90 grade oil is 1 197 783

 

There was also a LSD version made but this is like hens teeth now and the part number is 1 121 457

 

The above is not gospel, it’s just my findings and is wrote in the hope that it may be of help to someone. If I knew a fortnight ago what I know I would not have been taking my diff out for no reason. Oh and I can also refer back to it in a few years when I have forgot what I have learnt…

 

Jason

 

 

 

 

 

 

Edited by - jason fletcher on 26 Apr 2012 19:38:52

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Quoting zetec: 
Top bloke,ive secured 2ltrs of it from fords,collect & oil change this weekend to see what happens.many thanks *thumbup*

 

Make sure they sell you the one of the part numbers I listed above as they may try and palm you off with an alternative which is a multi grade.

 

Let us know how you get on.

 

Jason

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Mic

 

I initially thought exactly the same and I have to say that if anyone else had suggested it I would have immediately dismissed it as complete 80llox and would not to tried the different oils. I am now 100% sure he is correct after filling with fresh oil of the same type and it's back to being quiet again.

 

I can’t stress enough how different the differential behaved with 4 oils I tried. OK the 80w140 was out of spec for the diff but the other 3 were in spec and all produced noticeably different results.

 

Jason

 

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I have had a not dissimilar experience with my 6 speed gearbox. It was impossible (and I mean impossimpe) to get into 4th gear. Changed oil, and then it re-appeared. Funny thing was that the GL4 oil I had was Mobil, and when I told Phil at R&R he looked at me like I was from another planet using Mobil oil in a 6 speed box!

 

My diff is... loud. Have tried to source the Ford stuff you suggest, but it's not possible. Will try an ELF oil that my neighbour tells me is the dogs. If it works I will post it here.

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Regin

 

I'd try a few Ford dealers to see if they have any old stock on the shelf. I managed to find 3 litres in Swansea only last week.

 

Edited to say it was the LSD one I found in Swansea. I have recently bought the normal version on Ebay

 

Jason

 

Edited by - Jason Fletcher on 26 Apr 2012 15:39:03

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I have now changed the oil from the Catehram GL5 to Elf Tanself TRZ, which is "just" GL4.

 

I chose the GL4 oil due to the vintage of the construction. And because the manual says "under no circumstances use GL5" for the gearbox. Guess the internals have approximately the same "technical age".

 

I haven't driven the car yet, but just from pushing it I can tell that the diff is much quieter.

 

As I have a ZF LSD I will add a Redline LSD additive, which is due to arrive tomorrow.

 

The usual grrrrrr when I am pushing the car has disappeared. I was under the impression that there was not enough play from that sound, and am rather surprised that the oil has made that noticeable difference.

 

As I was clearly mistaken, I will change once again, this time to a GL-5 oil *redface* *redface* *redface*

 

Edited by - RJ on 2 May 2012 18:38:22

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Jason, ive collected ford straight 90 diff oil ( they use it for ford rangers diffs!?)

& its in place ready to be tested.

Ive got a live axle with quaiffe atb in but its a bit whiney, phil said to give this oil a go & see what happens. Just need a sodding dry day now.

The oil i took out was like water compared to this 90 stuff

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I initially misread this as the diff needing GL4, I got very worried until I realised it was the diff needing GL5.

 

An aside, a website called parts reunited has a bloke from Abertawe selling the LSD Ford oil as listed by Jason.

 

If anyone has a contact for the oil as listed by Jason other than this site it would be useful if you post up a phone number to put in the order.

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Probably worth someone who knows more than me about it to add a clarifying note at this point about the difference between the ATB LSD and friction LSDs, what their methods of action are, thus why they have different lubrication requirements and what those requirements are...

 

 

eg for Quaife ATB: 'Maintenance free design and retains standard axle lubrication' from the Quaife website here

 

Edited by - charlie_pank on 2 May 2012 21:54:03

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Actually, having looked at them on Google Maps, they may not be geared up for counter sales; will email 'em.

 

Edited to add:

 

From website: "If you choose to visit our trade counter in Rochdale, you will be greeted by our professional staff who can offer advice and guidance to help you select the correct product for your requirements."

 

So they are set up for counter sales *redface*

 

Question still stands, then!

 

Edited by - jingars on 3 May 2012 09:11:40

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