Lotus Elan

Diff leaking through pinion nut thread

PostPost by: TroonSprint » Tue Mar 18, 2014 12:16 pm

My diff was leaking round the pinion flange, so I have taken the pinion flange off and replaced the oil seal, using a Speedi Sleeve to make good the surface on the flange shaft. I carefully put the nut back the exact number of turns and have checked that the torque to turn the flange isn't too high. Now the oil is leaking down the screw thread.

As far as I can see from the manual and other internet articles there isn't another seal in the front of the diff, so how do I stop the oil coming down the thread? Is it the crush sleeve that will be at fault? How does that prevent the oil leak? Can the crush sleeve be changed from the front?

As always, all advice gratefully received.

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PostPost by: alan » Tue Mar 18, 2014 12:56 pm

i think the diff should have a breather or maybe it's blocked
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PostPost by: Keith Scarfe » Tue Mar 18, 2014 1:24 pm

In my experience, this is a common problem. You don't seal the threads on the pinion but you seal the prop flange (and the 4 nuts and bolts) to the pinion drive flange using silicon or hylomar or such. The space inside then fills up with oil (then stops when full) but doesn't leak out. That is how I have stopped this type of oil leak on these type of diff's before.
HTH.
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PostPost by: TroonSprint » Tue Mar 18, 2014 1:45 pm

1. It won't be the breather because the diff is not in the car and it leaks simply sitting doing nothing. The fill plug isn't tight, so there can't be any pressure inside.
2. The idea of sealing the prop shaft to the flange never occurred to me and seems like a compromise. Surely the diff can be made not to leak without resorting to that? But I can certainly do that if all else fails.

What about this crush spacer, friends? What role does it play, and is it the part that prevents oil coming down the thread?

Keep 'em coming please.
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PostPost by: Jentwistle3 » Tue Mar 18, 2014 7:42 pm

Could the oil be going under the speedy sleeve?
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PostPost by: Chancer » Tue Mar 18, 2014 7:47 pm

Could it be leaking between the speedi sleeve and the shaft? Are you supposed to use sealer between them?

The crushable spacer plays no part in the sealing of the differential.

I have had minor leaks along the splines and out through the back of the nut, I usually put up with them but I once refitted the pinion with blue hylomar on the splines and it stopped the leak.

The propshaft/pinion sealing would work and avoids disturbing the pinion pre-load, in theory you are supposed to use a new spacer and reset the pre-load, in practice redoing up the nut to the same position (marked before removal) works just fine.
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PostPost by: TroonSprint » Wed Mar 19, 2014 9:36 am

Thanks for your thoughts. It is most unlikely to be getting under the Speedi Sleeve, which is a very tight fit and has Wellseal between it and the shaft. I have put the nut back on with Wellseal on the threads and will see if that stops it.
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PostPost by: AHM » Wed Mar 19, 2014 10:30 am

it is common for oil to find its way along the root of the splines and the thread. Use a little sealant on the splines.

The torque for re-tightening the pinion nut against an already crushed crush spacer is in the manual.
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PostPost by: 512BB » Wed Mar 19, 2014 11:40 am

Mike,

I can assure you, that no oil is leaking down the threads.

As Simon, above, states, it is flowing down the splines. It then flows around the nut and fills up the void, it does not get anywhere near the threads.

What you need to to is this, or your diff WILL leak.

Undo the nut again, and take off the flange. Degrease, or deoil, the flange, and in particular the splines, the nut, and as best you can, the splines on the pinion. Place the flange back on. Run a thick bead of quality silicone in the recess that the nut sits in, up against the splines. Put some thread locker on the threads. Replace the nut.

LEAK FREE DIFF. At least from the front end anyway.

Ideally, you should replace the crush spacer, as it is pot luck if the diff will be silent, having messed with it. And a little tip re the sleeve you fitted. All you needed to do, was to get the flange in a lathe, and emery down the offending rough area to a mirror finish, where either rust has affected, or wear taken place. The front oil seal will allow for quite a reduction in diameter. That is what I did here on all the diffs I rebuilt: lotus-parts-f33/recon-differentials-for-sale-t18555.html

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PostPost by: TroonSprint » Wed Mar 19, 2014 3:57 pm

All you needed to do, was to get the flange in a lathe
Ah, there's the rub as Shakespeare would say.
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