Lotus Elan

Elan Differential oil

PostPost by: bloodknock » Sat Apr 13, 2019 6:35 pm

Hello gurus
Excuse the naievety of an old fart but,......Ive just drained a 3.77 differential unit ive recently aquired for my sprint. I am from the period of history when the good old golden Hypoy 90 was king in diffs, even though it stank to high heaven.
When I drained this unit the oil was jet black and didnt posess the anticipated aroma. It looked just like graphite grease in liquid form. I purchased the diff from a reputable source. But you know what they say "Trust but verify" So, my question is.....Is there a proprietary gear oil out there that this could be?
So, from the great resource of real technical knowledge out there,Please advise.
Regards
Bob
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PostPost by: nmauduit » Sat Apr 13, 2019 8:49 pm

was the oil supposed to be fresh?
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PostPost by: rgh0 » Sat Apr 13, 2019 10:52 pm

it may just be old and oxidised. I dont know of any modern gear oil that is black when new.

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PostPost by: Elan45 » Sun Apr 14, 2019 4:00 am

I've just recently drained the diff from my pre-airflow coupe. I wouldn't be surprised if it wasn't the same lube it left Cheshunt with in 1966. Over the life of my coupe, it sat for many years behind the Jag dealer in Little Rock Ark. The day in July 1978 when we pushed it onto the trailer for a ride to her new home in Ohio, it was a balmy 104 degF. After getting her roadworthy, I drove her for the next 6 years. Part of the time she was off road this last time was spent inside a 40 ft long shipping container where the summer heat baked her. That was 30 years ago. She has now followed me to Florida and a well deserved restoration. Surely that heat would have baked the diff oil, but it presented that nice golden brown that I expected to see.

It will be refilled w/ Redline gear oil.

Roger
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PostPost by: vincereynard » Sun Apr 14, 2019 8:42 am

Perhaps a P.O. put some Molyslip in the diff ? Does it feel gritty?
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PostPost by: bloodknock » Sun Apr 14, 2019 9:48 am

The diff feels great, minimal detectable backlash. Like I said I got it from a reputable source, I was just surprised to see the oil black.
When I "swish" the oil in my container it looks like very fine, not gritty, carburundum is supended in the oil. Is this what Molyslip looks like?
How would molyslip affect the diff? if at all. I fear the effects of non specified oils and additives being used. Would the addittion of Molyslip be a normal practice?
Thanks all
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PostPost by: Donels » Sun Apr 14, 2019 4:55 pm

It won’t tell you what the black stuff is but there’s a really good article on diff oils in the preceding article on Quaife gearboxes.
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PostPost by: 661 » Mon Apr 15, 2019 8:09 am

In the S4 I used to use hypoy 90 as you mention , but for several years have used Redline 75/90 NS
In the race diff I use Motul 75/140 as recommended by TTR (they use in both diff and gearbox)
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PostPost by: rgh0 » Mon Apr 15, 2019 1:05 pm

The English racers also rebuild their gear boxes every year despite following that recommendation from TTR and i am not sure why as my identical Quaiffe boxes behind more power than an FIA engine makes last 5 to 10 times as long , ??? Perhaps I am a more gentle driver or perhaps the oils I use work better ... who knows.

I am sure Motul make good oils and they should at the price they charge ( like Redline) but I am not sure why you use excessive oil viscosity in an attempt to improve lubrication of heavily load diffs and gearboxes. The higher viscosity and higher film strength at high temperatures help but with higher viscosity but there are downsides in terms of how it works with syncro gears and how it works at lower temperatures and the overall power lower int he gears. And this is without getting into the subtleties of base fluids and additives.

TTR seem to have a marketing "alliance" with Motul, I take all commercial specific brand recommendations with a grain of salt. i prefer specific technical recommendations and then base my brand selection based on that.

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PostPost by: denicholls2 » Mon Apr 15, 2019 8:58 pm

Might be someone felt a graphite additive was a good idea. Another vote for Redline here.

Sitting in the sun won't get your diff as hot as a lap or two around the track will. Even if you live in Death Valley.
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PostPost by: RichardHawkins » Mon Apr 15, 2019 9:50 pm

Bob,

When I rebuilt my diff I used new old stock crown wheel and pinion parts from Sue Miller. Both gears were black. Steel gears are usually bright. I think the gears were black due to heat treatment, and I expect this black surface to wear off. Perhaps this is the cause of black oil. As my restoration is taking so much longer than I hoped the car has not run yet so I don't know if the oil will turn black.

Oil analysis is a proven industrial tool used in predictive and preventative maintenance. If you really want to know, have your oil analysed. I just did a quick Google search and it seems analysis cost £30 - £70 depending on how much detail you ask for.

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PostPost by: 661 » Tue Apr 16, 2019 8:22 am

rgh0 wrote:The English racers also rebuild their gear boxes every year despite following that recommendation from TTR and i am not sure why as my identical Quaiffe boxes behind more power than an FIA engine makes last 5 to 10 times as long , ??? Perhaps I am a more gentle driver or perhaps the oils I use work better ... who knows.

I am sure Motul make good oils and they should at the price they charge ( like Redline) but I am not sure why you use excessive oil viscosity in an attempt to improve lubrication of heavily load diffs and gearboxes. The higher viscosity and higher film strength at high temperatures help but with higher viscosity but there are downsides in terms of how it works with syncro gears and how it works at lower temperatures and the overall power lower int he gears. And this is without getting into the subtleties of base fluids and additives.

TTR seem to have a marketing "alliance" with Motul, I take all commercial specific brand recommendations with a grain of salt. i prefer specific technical recommendations and then base my brand selection based on that.

cheers
Rohan


For the record, my gearbox was built by Alan Henderson and he recommends Millers Nano CRX 75/110 NT+
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PostPost by: Elan45 » Fri Apr 19, 2019 1:45 pm

I should also mention that I have a can of Molibdnium disulfide powder that I mix with small amounts of motor oil in an old 35mm film canister for my engine build cam prelube. It is quite black and I suppose if some one were to mix even a tiny bit (perhaps 5 or 6 cc) in w/ the diff oil, it would probably make the oil black.The powder I have is such fine particles you'd never see it when swishing around the oil, but then I'm sure the powder comes in various particle sizes.

I also remember adding a little bit to the waxy chain lube I used on my bicycle chain. You do not want to get that on your clothes. I used to ride several thousand miles a year, so I perceived it to be a performance enhancement

Roger.
'67 Elan S3 SS DHC
'67 Elan FHC pre-airflow
'67 Elan S3 SE upgrade to 26R by Original owner
'58 Eleven S2 (ex-works)
'62 20/22 FJ (ex-Yamura)
'70 Elan +2S RHD
'61 20 FJ project
'76 Modus M1 F3
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PostPost by: bloodknock » Tue Apr 23, 2019 7:14 am

My thanks to everyone. I am now much more comfortable with the "black look" of the oil. I am very pleased with the diff, it looks in as new condition with minimal back lash and light even face contact.
Cheers
Bob
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