Hi Michael,
As more than just a few people have experienced, adding sealant will
work for a short time and then begin to leak once the initial bond
breaks down due to relative movement. The problem is really that the
rear housing doesn't have enough fasteners for the loads it
experiences and the flange faces move around in use.
We have to give the sealant a fighting chance and use it within its
intended range of flexibility if we want it to stay oil-tight. Even
the best sealant will only stretch so much before it fails and this is
known as elongation. A very thin film of sealant can only move a very
small amount before failing and that is all that is happening in the
OD flange.
A simple way to reduce elongation as mentioned earlier is to increase
the thickness of the sealant so the movement of the faces represents a
much smaller percentage of the sealant. Grinding or cutting a groove
around the gasket faces for the sealant to fill achieves this nicely
and as long as it is all clean and dry during assembly with a modern
silicone sealant there will be no more leaks.
Andy.
On 11/10/16, Michael Salter <michaelsalter@gmail.com> wrote:
> *"The internal stresses resulting from the hydraulic clamping forces might
> be a more likely source."*
> This statement had me wondering as it sounded like quite a plausible
> explanation for the leakage issue that people are experiencing at the
> overdrive clutch ring joint however, sadly, if one studies where the
> hydraulic pressures are applied in the overdrive unit it becomes quite
> apparent that the hydraulic forces serve to pull the clutch ring in toward
> the forward casing of the overdrive during overdrive operation which makes
> the joint tighter.
> During "normal" non overdrive operation the 8 springs in the unit do tend
> to push the rear housing away from the clutch ring but that force is not
> that great as it is only required, by way of the cone clutch, to overcome
> overrun loads. Probably less than 150 lbs.
> All that said however I can certainly understand what Andy is saying about
> the likelihood of leakage occurring when the joint is assembled dry as per
> the Workshop Manual..
> Installing gasket(s) between the casings and the clutch ring will affect
> the sunwheel end float which is specified as 0.008" to 0.014" but adding a
> thicker end float adjusting washer could take care of that, if you can find
> an appropriate one.
> I would imagine that sparing use of sealant alone would have little or no
> effect on the end float.
> Michael S
> BN1 #174
>
>
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