Gearbox mounting fracture.

[Forumadmin]

Chris reported a vibration on the Javelin last year so I investigated with the car on the lift.
I found this.



The old perished rubber was removed.
The sheared mounting was welded up in situ. Extra weld was put on to strengthen.
Two of the layrub bolts were loosened to allow some axial movement. The new rubber was inserted by using a little persuasion with a scissor jack to move the gearbox forward. The rubber ring was cut and I do not think this will have any detrimental effect. I thought about gluing it back together but did not.


The wood on another jack to lift the gearbox for chassis bolt alignment.
The engine was prized back axially to allow fitting of the 4 plate fixing bolts.
Two extra washers were put between each of the four bolts holding the rubber holding plates together.The washers were held with some masking tape on a screwdriver to aid insertion.The mounting was checked for ability to rotate.

[RandalColman]

Good photos, Keith. I have seen a few of these brackets either cracked or repaired, so I hung onto some spare ones I was given. It seems that Jowett increased the thickness at some point, but only from about 2.4mm to 2.8mm. They may have found it difficult to press anything thicker into the conical shape. I don't know if it is conventional to stress-relieve parts that small, but it is clear that the residual stresses from the pressing and welding would have made it susceptible to fatigue.

If the washers you mention are sandwiched between the cupped plates holding the rubber rings then, as you are probably aware, softening the rear mount can lead to clutch shudder. I think there was something in the service bulletins about that. The whole engine is pulled backwards when you press the clutch, so if it is free to jiggle back and forth there is a feedback effect on the clutch engagement.

[Keith Clements]

You add washers to make sure the mounting is just free to turn on the gearbox output housing. If it does not turn then you are likely to crack the clutch housing. It is possible that the rubbers rust solid, so a periodic check is advisable. There should be no axial movement.
In my case the rubber had become fluid and oused out, so was due for replacement anyway. This did give some axial movement and some clutch judder which may have hastened the mounting failure .

I also went around many nuts and tightened them. The oil leak you see hopefully is now cured. The nuts holding the output tube took half a turn each! Perhaps I am getting stronger in my old age. Worth doing a 'spanner check' whenever you have chance. Something I learnt off John Blanckley when rallying with him. Although in these days of thread lock it is less necessary.