Lotus Elan

Diff Drip

PostPost by: theelanman » Wed Jul 15, 2015 8:58 am

Ive got a very small leak starting from my input shaft (propshaft) into the diff.......
Im going to keep an eye on it....but anything I should be worried about?.......
Im wondering if the slight rumble I get to the rear as I pass 70mph is to do with a possibly off balance propshaft....which in turn is what has created my 'drip'
thoughts......????

the amount of oil Im losing judging by the patch on the garage floor is about a teaspoon a month......
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PostPost by: terryp » Wed Jul 15, 2015 9:12 am

Gareth
Hope you are well!
I reckon the leak is pretty normal, I had a similar one on both +2's I had. The Elan doesn't leak (yet) as I changed the seal when the diff was out.
Rumble is possibly output shaft bearing or wheel bearing wear.
Ouput shaft bearings and front seal can be replaced in situ but its a bit of a job. Quite easy when its out the car :wink: (Just have to mark the nut position)

All the best

Terry
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PostPost by: theelanman » Wed Jul 15, 2015 10:22 am

Terry
thanks for that......
Ive got the new CV drive shafts to put on at some point so I think Ill probably wait until I do that.....
but glad to hear its a 'standard' feature......... :D
cheers
G
ps it feels like years since we were 'en poitou'.......... :(
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PostPost by: Satyr-Icon » Thu Oct 15, 2015 3:49 pm

Hi elanman,

The drip from front of diff is only a standard feature when pinion oil seal has been replaced without extracting old pre-load crush spacer. A new one is meant to be used every time the output flange is removed or even released.
Spacer is designed to collapse partially after reaching a predetermined compression and apply pre-load to inner race of pinion bearing.
Pressure between rear face of flange - to spacer - to inner race - to pinion shaft usually forms an effective oil seal when flange securing nut is tightened to correct torque setting. The crush spacer does not recover from first compression and will no longer apply required pre-load to pinion bearing or the necessary pressure to form a seal so the diff oil can't seep down the splines between the shaft and the splined collar of input flange.

The cavity formed by propshaft flange and diff flange partially fills with oil and is slung out past the mating surfaces of the two flanges when oil warms up and viscosity drops. Evidence of oil slinging can be seen on bodywork above prop/diff flanges. If the slinging is evident in line with flange mating surfaces, the oil is coming down the splines as above. If in line with oil seal, you know the rest.

I had to replace front diff oil seal and no crush spacer was available so I reassembled without. Much reduced leak but still a very slow drip and evidence of oil slinging above flanges. Would have to remove new oil seal to fit new spacer so I stopped leak by applying sealant to prop/diff flanges.

Pinion bearing pre-load helps to reduce diff backlash and wear of pinon/crown wheel and noise to a certain extent. Loud deeper rumble is usually rear hub bearings, outer ones almost always go first.

Just a thought here, I have a pair of the proper Lotus rear hub pullers ( right and left hand thread ) with the Sykes Pickavant hydraulic rams. Happy to make these available for use by forum, not sure how to do it here.

Intend to do the job properly when I can get around to it.

Anybody have some round 'tuits' they could sell to me? :lol:

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PostPost by: john.p.clegg » Thu Oct 15, 2015 4:07 pm

You can borrow mine if you want...

2015_1015tuit0001.JPG and


John :wink:
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PostPost by: ericbushby » Thu Oct 15, 2015 4:14 pm

I have had a slight drip for a couple of years, not much, just a piece of cardboard on the garage floor to keep
the floor clean.
Then this year it has rapidly got worse. The piece of cardboard became a sheet and then a drip tray on top of that.
It needed topping up after two or three trips out.
It is now at the menders being stripped and rebuilt with new bearings and seals all round.
So keep a close watch on it,
Eric in Burnley
1967 S3SE DHC ( off the road again )
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PostPost by: RichC » Fri Oct 16, 2015 6:24 am

thank you satyr .. very interesting !
am getting round tuit this weekend . glad to hear there's a simple solution .
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PostPost by: Grizzly » Wed Oct 28, 2015 5:49 pm

This is a very interesting thread.

Not too long ago i replaced all my Diff seals because it wouldn't hold oil, i filled it up with oil and refitted the diff only to find it still dripping on the garage floor a couple of weeks later. I had written it off as 'a Lotus thing' but as its not difficult to remove i might revisit it and fit a new crush spacer.

Is it a case of removing swapping it and tighten back up to the original marks?

I am just looking at the parts picture and am i correct in saying its no. 11
RB.gif and


This Chap (for reference is SJSportscar part number SJ026R0001)
SJ026R0001.jpg and


Or http://www.ebay.co.uk/itm/Ford-English- ... XQwwlR-rjC
Chris
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PostPost by: Satyr-Icon » Thu Oct 29, 2015 11:17 am

Hi Grizzly,

New seals don't always guarantee no leaks. Variations in design etc. mean the 'established' sealing point may not coincide with where the new seal dictates it will be. The entire machined surface of O/put shafts and collar of I/put flange should be polished up with 400grit 'wet o dry' before assembly. Even momentary contact with a 'CRUSTY' bit on a shaft or collar can ruin a new seal.

Even a wear 'trench' in the collars can be dodged with a new seal but this can be a bit of a risk.

Another very important point to mention is the DIFF has a 'breather' on the top of the casing. It is essential this is clear.
The DIFF gets hot, very hot, in excess of 100C, the boiling point of water at atmospheric pressure, after 15 mins. at motorway speeds :D This heat will pressurize the ' hot oil gas' in a DIFF with a blocked breather. The pressure will tighten the seals on their mating surfaces and greatly increase wear.
The breather is often overlooked and will make an otherwise well done job look like an exercise in futility and much scratching of heads.

In your particular case (Grizzly) I would try to locate the exact location of your leak or leaks and apply the above if you have leaks past new seals.

As for the 'crush' spacer, you will need a new front oil seal since it must be removed to get access to the spacer. Removal of F/oil seal always destroys it as far as I know. Remove old spacer with two needle nosed pliers (can be a problem if flange nut has been grossly over tightened) fit new over splines, press in new seal,
polish up and 'oil' flange collar before fitting in seal.
Tightening the 'nyloc' nut to the correct torque should apply the correct pre load to the bearing. The crush sleeve is a 'use once only' and does not recover once deformed so releasing the nut after initial tightening is a 'no no'.
As far as I know, there are no matching marks for the flange to DIFF fitting but if there are any I would use them. The propshaft should be balanced in any configuration but again if there are marriage marks I would use them.

I use a bit of gas fitters 'BOSSWHITE' on the PROP/DIFF flanges because the new crush sleeve does not ALWAYS guarantee a good seal. Only a small amount is necessary and fitting the propshaft should happen while the 'Bosswhite' is still wet.
If it's any consolation to you, I have only ever seen two totally 'DRY' diffs on Elans out of around 100.

Let me know how you get on.

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PostPost by: Grizzly » Sat Oct 31, 2015 12:13 pm

Satyr-Icon thanks for the write up.

It's funny you should mention the breather, when i removed my Diff i rolled it out of the chassis so it came out upside down. I was expecting some leakage from the breather but it remained dry, so i took it apart and was blocked up (so that won't help)
Chris
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