Lotus Elan

Strange noise and vibration

PostPost by: prezoom » Thu Dec 19, 2019 2:49 am

Another check would be to see if both U joints are running in plane. An Angle Finder on the front pulley, then record the angle, then do the same on the diff flange. If they are not the same, the gearbox tail shaft can be adjusted with different spacers at the gearbox mount to the chassis.
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PostPost by: rgh0 » Fri Dec 20, 2019 11:58 pm

fireblade wrote:Paul


I too have experienced a strange noise and vibration from the rear drive at speeds between 60-70 mph in 4th gear. Replacing the oil in the diff with MTL didn't change the situation. Coincidently the diff bearings started to become noisy so I removed the diff and prop shaft and had the diff bearings replaced along with new UJ's and the prop shaft balanced. The Lotus technician who has 30years+ experience who did the work for me advised I should revert back to Castrol EP80 which I did. The car now drives like a dream with no hint of noise or vibration.


I suspect the rebuild has more to do with it rather than the oil

Castrol EP 80W is a GL-4 oil and not suitable for hypoid diffs. Redline MTL is also not a suitable oil for hypoid diffs as it is also a GL-4 oil

Hypoid diffs like in the Elan which require oil designed for sliding contact gear teeth should use a GL-5 oil.

I use Redline 75W-90 gear oil, this is a polyolester base oil which gives it superior temperature resistance and thus a long service life in a diff where it can get hot but its expensive . Castrol EPX 85W-90 is a cheaper mineral oil based GL-5 alternative that will work but with a shorter service life especially if you use your car hard and which will probably give reduced wear protection in the long term.

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PostPost by: 2cams70 » Sat Dec 21, 2019 1:57 am

rgh0 wrote:Castrol EPX 85W-90 is a cheaper mineral oil based GL-5 alternative that will work but with a shorter service life especially if you use your car hard and which will probably give reduced wear protection in the long term.


Almost all live axle cars (Fords included) have had "sealed for life" lubricant in their rear axles since the mid 1960's. There's no drain plug fitted. Over the years I have removed countless English axle centres from various Fords in scrapyards many having covered several 100,000kms. Included in this are hard worked commercial panel van vehicles, Twin Cams and vehicles with 2.0L Pinto engines (2.0L Pinto engined Panel Vans included).

All I can say is that the Ford English axle is a very sound design and once again I take my hat off to all the engineers who designed the 997cc 105E Ford Anglia way back in 1959. This car is the original source of the majority of all the goodies that make up the components of all the cars we cherish so much these days.

The only failures of note that occurs to English axles not subject to extreme abuse are damage due to lack oil caused by failure of the pinion seal and also loss of preload of the pinion bearings caused by the pinion nut coming loose (this too can also cause oil leakage as it enables a leakage pathway through the splines). I've never seen a badly worn crown wheel and pinion or worn bearings otherwise. I think this speaks volumes about Ford's decision to use a regular mineral Hypoid lubricant SAE 90 grade in their axles in a car used normally on the road. I reckon they made the correct choice.

I forgot to add that these days a mineral "Limslip 90" or LS90 rear axle oil is about the closest you can get to the original specification. You don't need a multigrade oil - eg. 75W/80 or a dual purpose manual transmission / rear axle fluid. The extra Limited Slip additives in LS90 for an LSD differential are no problem if your axle is not fitted with an LSD.
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PostPost by: rgh0 » Sat Dec 21, 2019 3:40 am

Ford chose a GL-5 type EP-90 oil for the orginal Live axle "english diff" because synthetics were not available back then, not because it was superior to synthetic oil in any way. Also live axle cars have a larger oil amount in the live axle and superior cooling than in the Lotus version due to the larger surface area and it hanging down below the car rather than being set up in the chassis with a smaller amount of oil and limited air flow around it, so the mineral oil will last longer in the live axle cars. "Sealed for life" for most car manufacturers basically means you do not have to change it during the warranty period, what ever that meant was back then, and what ever it is now for new cars.

For the majority of our Elans that have relatively little use and most of it gentle summer touring driving then a mineral oil is "OK" but I would not consider it "Optimum". I don't use mineral oil based lubricants because I use my cars harder than most and do more miles than most and have been doing so for 40 years and I see synthetic lubricants as clearly superior. I do it also because I work with large industrial gear boxes in my professional life and spend a lot of time studying lubrication technology and tracking gear box life and performance ( efficiency, wear etc) and understand the benefits of modern lubrication technology in both modern and old gearboxes.

The world of lubrication has moved on a long way in the last 40 years. Group 2 and group 3 base oil mineral oils are better than back then due to superior base oil refining techniques and better additive packages and modern group 4 and group 5 synthetic base oils better again.

I have also drained lots of diffs that have used traditional group 2 mineral oil like Castrol EPX 85W-90 or its older equivalents for many years and generally it comes out "black" and smelling "burnt" compared to diffs using synthetic group 4 or group 5 oils where it comes out looking and smelling like new. Group 3 highly cracked mineral oils are allowed to called "synthetic" and perform somewhere in between traditional group 2 mineral oils and group 4 and 5 true synthetic oils.

If debating the merits of oils you need to start with which base oil group you want and why and l then go to the additive packages you want and why and which GL lubrication type you want and why . All else is subjective "feel" based on subjective data and personal observation and preference which may be valid in the individuals circumstances but may not be universally true.

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Rohan

PS I also grease my trunions - hahahaha :lol:
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PostPost by: 2cams70 » Sat Dec 21, 2019 4:38 am

rgh0 wrote:Also live axle cars have a larger oil amount in the live axle


Not true. A live axle car is not filled to a level that includes oil entering the axle tubes.

rgh0 wrote:hanging down below the car rather than being set up in the chassis


Maybe true - although probably only an issue under race conditions when circulating oil through a separate cooler may be a better option. A Lotus Elan is a light car (lighter than the Fords the axle was designed for) which does help lessen the loading on the gears.
rgh0 wrote:
"Sealed for life" for most car manufacturers basically means you do not have to change it during the warranty period, what ever that meant was back then, and what ever it is now for new cars.


Having worked for two vehicle OEM's I take offence at this because that hasn't been my experience working in the automotive industry. Most if not all manufacturers take their reputations very seriously with decisions (engineering related ones at least!!) made using deductive reasoning and empirical data based evidence.

rgh0 wrote:I have also drained lots of diffs that have used traditional group 2 mineral oil like Castrol EPX 85W-90 or its older equivalents for many years and generally it comes out "black" and smelling "burnt"


Yes it always comes out a dark colour but this is subjective and not evidence that the oil has actually failed in its ability to perform it's function and adequately lubricate.

rgh0 wrote: I don't use mineral oil based lubricants because I use my cars harder than most and do more miles than most and have been doing so for 40 years and I see synthetic lubricants as clearly superior


May or may not be true in an automotive axle never designed for synthetics and not being extended well beyond it's original design intent. It's true that OEM's are canny and won't spend extra money if there is no able to be realized benefit in doing so.

Jeez - I reckon there's definitely some secret ingredient "smelling salts" that Redline put into their products judging by the passions raised whenever any discussion comes up about them!!
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PostPost by: rgh0 » Sat Dec 21, 2019 5:26 am

2cams70 wrote:
rgh0 wrote:Also live axle cars have a larger oil amount in the live axle


Not true. A live axle car is not filled to a level that includes oil entering the axle tubes.

rgh0 wrote:hanging down below the car rather than being set up in the chassis


Maybe true - although probably only an issue under race conditions when circulating oil through a separate cooler may be a better option. A Lotus Elan is a light car (lighter than the Fords the axle was designed for) which does help lessen the loading on the gears.
rgh0 wrote:
"Sealed for life" for most car manufacturers basically means you do not have to change it during the warranty period, what ever that meant was back then, and what ever it is now for new cars.


Having worked for two vehicle OEM's I take offence at this because that hasn't been my experience working in the automotive industry. Most if not all manufacturers take their reputations very seriously with decisions (engineering related ones at least!!) made using deductive reasoning and empirical data based evidence.

rgh0 wrote:I have also drained lots of diffs that have used traditional group 2 mineral oil like Castrol EPX 85W-90 or its older equivalents for many years and generally it comes out "black" and smelling "burnt"


Yes it always comes out a dark colour but this is subjective and not evidence that the oil has actually failed in its ability to perform it's function and adequately lubricate.

rgh0 wrote: I don't use mineral oil based lubricants because I use my cars harder than most and do more miles than most and have been doing so for 40 years and I see synthetic lubricants as clearly superior


May or may not be true in an automotive axle never designed for synthetics and not being extended well beyond it's original design intent. It's true that OEM's are canny and won't spend extra money if there is no able to be realized benefit in doing so.


I do love a lubrication discussion. :D

Yes the quoted refill amount for an english axle diff on an escort is 1.1 litres ( never bothered looking at up before) versus 1.2 litres for the Elan diff. But since its "sealed for life" no one ever refills their english axle diff, so no one knows what the correct level is ??? (sorry for being a little sarcastic ) What I do know is these live axle diffs fail on the track as oil drains into the axle tubes on heavy cornering unless you fill them with more than the quoted amount than you put in an Elan diff !

I am sorry you are offended by description of what "sealed for life" means and car company ethics but to make a claim of "sealed for life" without defining what "Life" means is just a BS marketing claim not an engineering term. I was merely trying to define "life" what is the engineering based car company definition of "Life" in your experience.

The oxidation description I gave was subjective but the oxidation itself experienced more rapidly with mineral oils is not. Black oxidised oil will lubricate more poorly than un-oxidised oil. Oxidation is the principle determinant of oil life in a differential.

As I said, you do not "Need" to use a synthetic oil in a Lotus Diff. Gears are gears whether old or new. You dont "Need"' to use it in you 2019 Golf or Porsche either but it is a good idea to use it in both IMHO and Golf and Porsche specify synthetic oils these days due to its better lubrication and longer life. The only Caveat I would apply is that if you use mineral oils watch the maximum operating temperature and reduce the change frequency based on that ( of course you all have diff temperature monitoring gauges?) . Also recognise that mineral oils are not as slippery as synthetic oils and that you will have higher HP losses ( about 2 to 3% of power transmitted higher ) and higher temperatures and less power to the road in a mineral oil filled diff due to this.

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PostPost by: 2cams70 » Sat Dec 21, 2019 6:17 am

All I can say is this. I've removed many English axles form Ford cars that have covered several 100,000km that have never had an oil change and use the factory fill SAE 90 mineral Hypoid oil. Never seen a mechanical problem that could be attributed to oil breakdown. The synthetic oil may improve the axle durability but I have no evidence that it does at least in an axle that is used normally on the road.

Modern cars using synthetics is a whole different ball game as these cars will likely have been designed from the outset to use a synthetic oil. All the design, testing, and field trials will have been validated using a synthetic oil. Some of these oils will likely be manufacturer specific custom blends also. It makes sense in a modern car. You certainly wouldn't use a mineral oil in a modern car where the OEM had specified a synthetic.

To use a simplified analogy I wouldn't fork out for Redline for the sole purpose of lubricating my squeaky door hinges but maybe some of you guys would!

So John - did changing out the Redline MTL reduce your gear noise?? I bet you are too afraid to say!! I would be too!!
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PostPost by: rgh0 » Sat Dec 21, 2019 7:02 am

2cams70 wrote:
So John - did changing out the Redline MTL reduce your gear noise?? I bet you are too afraid to say!! I would be too!!


It looks like you personally define "life" as several hundred thousand Km's. It is still not an engineering term or the car companies definition and the basis for oil replacement or oil selection IMHO. What I do know is that as car companies car warranties and regulated general consumer warranties rights have grown in recent years "sealed for life" designs have declined - I wonder why.

As I said before things like noise, vibration and gear change quality are all subjective and I don't dispute peoples subjective experiences. Red line oil in a diff may make if more or less noisy depending on your subjective experience for your particular diff installation and driving style and depending on what is generating the noise in the first place. However a noisy diff is an indication of a mechanical problem and masking it with a different oil type is not solving the root cause problem. I am trying to have a science based engineering discussion of lubrication technologies and why you may choose one versus another. I am sorry if you or others feel intimated by the facts such as understanding the difference between a Gl-4 or Gl-5 gear oil specification and benefits and properties and usage of a group 2 /3 /4 /5 type base oil for gear lubricants but these are the key things you need to know and understand in any lubrication discussion. In the end its your cars and your decision on what you want to do.

I freely give people the breadth and depth of my Lotus experience supported by 40 plus years of being a mechanical engineer and dealing with engineering problems in both a professional sense and as a Lotus everyday driver and racer. I do that to try to minimise some of the wrong information that ends up on Internet forums due to errors made by people, I am not invulnerable to making errors also, but I try to research my topics well and always correct errors if I identify them.

Whether people choose to take my advice or not is up to them as individuals but if you want to have a debate about what I say then please bring hard engineering data so we can have a rational debate, not subjective opinions which may be valid but which cannot be countered without offence. Drawing a conclusion that synthetic oil is not superior to mineral oil in an Elan diff because you have pulled apart many old escort and cortina diffs and they have been OK is not a logical conclusion

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PostPost by: JonB » Sat Dec 21, 2019 8:49 am

Hello chaps!

I?ll say this: I chose to fill my gearbox with Redline based on Rohan?s and others? recommendations. My experience has been not great. Yes, it improved the gear change slightly (although I?d also overhauled the shift mechanism) but the box is now very noisy and it leaks more oil than the engine does, judging by the size of the puddle on my garage floor. Full disclosure: I fitted all new seals and gaskets to the gearbox, and used sealant on the Speedo drive. So I wasn?t expecting to see the very expensive Redline oil flooding the top cover of the box (this is where it looks like it?s coming from). That stuff is thin. I can only surmise that it is being flung about by the output shaft more than a thicker oil would be.

I?ve been following your discussion with great interest. You both speak authoritatively and with great articulation. But it seems to me, that if ever there was a situation where ?your mileage may vary?, this is it. I?m willing to bet Rohan?s gearboxes are not as worn as mine, for example, especially if he is racing. So.. maybe Redline is more appropriate for a rebuilt box than a knackered box? I dunno.

Regarding switching oils, I?ve not done it yet but you can be sure I will report on the result. Knowing my luck it?ll be worse!

Rohan, as to your greasing your trunnions, you should keep that quiet, or the Church of the Oily Trunnion will declare you heretic and come after you with pitchforks and flaming brands.. :lol:
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PostPost by: nmauduit » Sat Dec 21, 2019 11:01 am

JonB wrote:That stuff is thin. I can only surmise that it is being flung about by the output shaft more than a thicker oil would be.


I would think if there is a leak there is a leak, the apparent thinness of the oil at room temperature will not make a huge difference in the outcome...
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PostPost by: Craven » Sat Dec 21, 2019 11:49 am

Didn?t think you can overfill a Ford/Lotus Diff as filler plug hole is the correct level.
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PostPost by: JonB » Sun Dec 22, 2019 9:12 am

nmauduit wrote:
JonB wrote:That stuff is thin. I can only surmise that it is being flung about by the output shaft more than a thicker oil would be.


I would think if there is a leak there is a leak, the apparent thinness of the oil at room temperature will not make a huge difference in the outcome...


Problem is it appears to be coming from the gearshift ball joint. An assembly you cannot seal. It?s been tightened up (new bellows) and screwed in with a bit of RTV on the plastic thread.
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PostPost by: oldelanman » Sun Dec 22, 2019 12:04 pm

JonB wrote:Problem is it appears to be coming from the gearshift ball joint. An assembly you cannot seal. It?s been tightened up (new bellows) and screwed in with a bit of RTV on the plastic thread.


It's not coming from your new breather is it ?
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PostPost by: mbell » Sun Dec 22, 2019 7:37 pm

I am kind of surprised it coming from the stick, not much reason for much oil to end up in that part of the box and head up against gravity!
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PostPost by: JonB » Mon Dec 23, 2019 9:55 am

You?re not the only one, mbell! It can?t be coming from the breather alone because it?s lying in the other ribbed section of the cover. I wonder if the low viscosity of the MTL is to blame, partially. They do brag about that in their marketing. Maybe it?s being flung about too much. Or, maybe I overfilled it a little. I did put some more in when I had the cover off to replace the gasket as I knew I?d lost some.

And sorry to the OP for the thread hijackance...
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