Loose diff flange bolts S3

[englishmaninwales]

1 year ago (and about 5k Miles) I fitted a refurbished differential along with new oil seals. All last summer I had the pleasure of zero oil leaks from the rear of the car.
So I was surprised to see a small oil patch last week followed by a larger one today
On inspection all 3 oil seal showed no sign of leaking but it was clear that oil was leaking from the diff flange to carrier joint. All of the fixing bolts were loose.
I remember tightening these but on reflection maybe I should have used thread lock?
Any thoughts on this one?

Malcolm

[2cams70]

You don't need to use thread lock on these bolts provided you use the correct self locking nuts. These bolts will be the same as the ones used on Ford Escort/Cortina models and are available as new reproductions from:
http://www.stage1.org.uk/motorsports/in ... t/twin-cam.
The likely reason for the loss of oil from the diff flange to carrier joint is that pinion nut has come loose for some reason and the bearings have lost their preload or the preload was not correctly set in the first place. My experience is that if the pinion preload is correct (hence the nut is tight) you don't normally get oil seeping between the splines and out of the carrier. Some people use sealant "goo" on the splines to help prevent this but really it should not be necessary if the preload is correct and the nut is tight. Ford never specified for any goo to be used here.

I'd take the car back to whoever rebuilt the diff and have a whinge. Just because the diff is quiet does not necessarily mean the pinion preload has been set correctly.

[Foxie]

Had diffs out many times, but never had a leaking flange.

Always used silicon sealant and lock-nuts

[Foxie]

You do mean the main cast iron diff flange to alloy carrier, not the u/j drive flange on the pinion shaft ?

[2cams70]

Yes we need some clarification on the terms used:
In my part of the world at least "Carrier" is the complete nose assembly part fitted with all the gears and bolted by a ring of nuts to the separate "housing". "Diff flange" is the part that connects to the propeller shaft.

[englishmaninwales]

Ah, sorry! Incorrect terminology!
I?m referring to the bolts (8 or 9 I can?t recall exactly) that fix the differential assembly to the Lotus alloy housing
These were loose and the oil has been seeping from this joint, not the oil seals.
I used a new gasket (a slightly thicker gauge gasket on the advice of P Matty?s parts department) and silicone sealant along with new bolts and spring washers.

Malcolm
(I suspect user error in not tightening enough in the first place )

[Craven]

Maybe just another story! but it is said that you can get more leaks/seepage by using a gasket than sealant alone. I believe Ford did delete the gasket on late Escorts.
Fitting the thicker gasket must move the relative position between output shafts in the case and diff.

[2cams70]

The key is to always use a torque wrench to tighten nuts such as these. It's dead easy on a Ford but on a Lotus maybe access is difficult. In such cases what i normally do is tighten the nuts that are easily accessible counting the number of turns or fractions of a turn required to reach the correct torque figure. For the difficult to access nuts I tighten these according to the number of turns reached on the easily accessible nuts. Very rough method but better than tightening by feel alone!

I've never had problems with the standard thin gasket in this location. If I ever have doubts about any gaskets (eg. the poor quality paper one used on the timing cover) I cut better ones out by hand using the new crappy gasket as a template and using new high quality gasket paper of my choice for the final version. Better than using "gunk". Save that for new engines where it's OEM specified not an historic LTC.

[englishmaninwales]

Thanks. I used a torque wrench on re-assembly, but I must have made a mistake somewhere......The fixings are UNC bolts rather than studs/ locknuts as on the Ford axle, hence I wondered if threadlock should have been used?
I?ve tightened them now, although I shall try to get a small torque wrench on.
I?m not in a hurry to remove the unit at present to do the job properly as I use the car most days between now and November.
I shall top up with oil and periodically check the fixings.

Malcolm

[prezoom]

I would be concerned about just how thick a replacement gasket is used. A thick gasket will move the hogs head/pumpkin/whatever, forward and change the alignment of the output shafts in relation to the splines in the differential, which could cause unneeded wear on the splines and the stub axle bearings. I went through this with a differential change in a banjo style axle housing as used in a Cortina/Escort. Careful calculations were needed when making a spacer to move the pumpkin forward to get the correct alignment of the axles.

[promotor]

Regarding the diff gasket: all of the Lotus Elan final drive units I have taken to pieces have the heavy duty gasket in them (I've stripped approx 5 complete Lotus diffs in the last few months and they were all the same - thick original asbestos(!?) type gasket, and Wellseal so appear to all be factory builds).

Any diffs that come from an Escort or Cortina axle etc I use a thin paper gasket. Elan ones I use the heavy duty one. I too wondered about the thickness of the gasket affecting alignment of drive shafts but I suspect Lotus built this "thick gasket" factor into their design of the aluminium case.

[englishmaninwales]

Diff gasket (thick type) Paul Matty part RGSK026B
I?m told this is the only type that they now use in their workshop.
I?ll get a thickness measurement.

Edit: Thanks, Promotor, our posts crossed.

[Craven]

Lotus used copious amounts of RED Hermetite in their assembly; you will be left in no doubt if you come across one. Ones I?ve taken apart had Thin Paper gaskets.