Transmission tunnel knocking noise on T5-based 5 speed boxes

[kingzetts]

A point to note for anyone converting to a T5-based box, or who has one already and is trying to track down a knocking noise.

Where the handbrake lever attaches to the tunnel there is a large cutout or depression in the tunnel side. Where the captive nuts for the front retaining screws for the handbrake bracket are attached to the tunnel, just forward of the leading edge of this cutout, there is a vertical reinforcing flange which sticks out inside the tunnel.

Because the T5 tailhousing on most conversions causes the front propshaft UJ to be located further back inside the tunnel than the Jaguar box, the "ears" of the UJ yokes can end up very close to this flange, and to the vertical inner edge of the handbrake lever cutout.

Under the right conditions (in my case, tight right hand cornering under acceleration) the gearbox mounts allow enough lateral movement of the gearbox to allow the yoke ears to contact these metal surfaces causing a loud and alarming knocking noise.

I was able to diagnose the problem with the aid of an endoscope from underneath the car with which I was able to see that the clearance to the side of the tunnel cutout was about 2mm at most, and I could see the bright marks on the edge of the cutout where contact had occurred. I was able to gain enough access with the gearbox cover removed to knock the vertical flange backwards to increase clearance, but I had to use a slide hammer to create a bulge in the vertical front edge of the lever cutout to pull this metal away from the yoke ears.

This would have been infinitely easier without the gearbox in place but no way was I going to remove all that! So if you are planning a T5-based conversion I suggest checking clearance at this point carefully before you finally install the engine and box.

And before anyone asks for pictures, forget it - no way of getting a camera in there to produce meaningful images.