Nasty ‘Thud’ when changing up gears as load comes off gearbox

[JonathanT]

Hi guys, I could really use some advice here in helping me diagnose a loud thump. It happens when I’m changing up gear mainly particularly noticeable on 2nd to 3rd on a GTL . Is something that’s become manifested over the past month and I’ve a feeling it’s getting worse.

As I depress the clutch the engine of course, disengages or the drive disengages and I get a thump noise. I did wonder if it was the driveshaft. There is a really tiny amount of play in one of them, hardly detectable. But somehow I don’t think this is the culprit. Any ideas?

 

[Andy McGhee]

It might be worth checking that the gearbox mounting is okay - is there any vibration when you brake?

 

[jcarruthers2]

It does sound like the gearbox mounting. Jack up the car from the front, wedge a pry bar between the gearbox mounting and the front cross member and move back and forth and check for excessive movement (the rubber often has come adrift from the metal components, sometimes, it can be due to loose mounting bolts too).

If you are confident the gearbox mounting is ok. Run the same checks on the two engine mountings. Place a block of wood under the flat elongated part of the rear end of the gearbox and slowly jack up, note any excessive lift of the engine mountings.

 

[Nigelblandin]

Autodoc do the mount, not expensive and not difficult.