Differential oil and lesson learnt.

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The Pikey
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Differential oil and lesson learnt.
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
BBL
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Good to know, Mr. Fletcher. Thank you for taking the time to write it up in such detail for the benefit of us all. Please enjoy a rutabaga at your earliest convenience.

Smile Sean

Tony Whitley
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Mine whines like a bitch so I might try changing the oil
Pendennis
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If mine doesn't whine I want to know why\" class=\"smiley\" />\" class=\"smiley\" /> Very informative of you, well done
millsn
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Mine uses the Ford LS oil and is quiet too
zetec
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Top bloke,ive secured 2ltrs of it from fords,collect & oil change this weekend to see what happens.many thanks
The Pikey
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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 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
mic
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How long before you have to change it again, I find it hard to believe a session on the rollers would kill the oil.
The Pikey
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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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The Pikey
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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