Loud Crack Noise From Gearbox/final Drive?

[Guest edcotic]

i've got a loud (audible from outside the car) bang/knock eminating from the front left of the engine bay if i agressively get on or off the throttle.

 

It's a one off noise, also provoked by reversing from a standstill up an incline.

 

Had the car on the ramp yesterday, all bushes, bearings, engine mounts, intake, washer reseviour are fine.

 

When i got a mate to observe as i agressively popped the cluth in reverse, he reckoned it was definately eminating from the gearbox/final drive!

 

could something be moving inside and banging against the casing?

 

expert advice massively appreciated

 

Ed

[newdean0 0]

The downpipe is near the final drive and will hit the bulkhead/subframe if your bottom engin mount is badly worn, check for this by looking for any marks where contact has been made. Some of my mounts were pretty badly worn around the 120k mile mark though you can't really tell from just looking at them.

 

Also, if this is a 1.6 the front brake calipers can give a nasty bang when you stop then change direction from forwards to backwards or vice versa. Unless the gearbox is whining loudly or making any other funny noises during normal driving I doubt it's anything wrong internallly.

Edited June 16, 2006 by newdean0

[jackherer 543]

My mates 205 had a very similar sounding problem a couple of days ago, I was standing next to it listening when he let the clutch up and it sounded very much like the diff so he took the next day off work and we bought some new driveshaft seals and cleaned up one of my spare gearboxes. I got as far as taking the driveshafts out and when I was splitting the wishbone balljoints I noticed that the crappy powerflex wishbone bushes had gone and were allowing fore/aft play which was the cause of the noise.

 

In your case it may well be the diff, but have a good check of the wishbone bushes as there is no way I'd have spotted this without the balljoints disconnected and the wishbones free to be moved about.

[Guest edcotic]

thanks for the reply.

 

the car is a 1.6 running an MI16 with an uprated engine mount which still feels pretty tight do i'm doubtful that the downpipe is the culprit. Possibly the brake calipers tho - i shall investigate.

 

I checked the wishbone bushes with a bar while it was on the ramp the other day - they seemed tip top.

 

when u say 'it could be the diff', what exactly could it be?

 

Cheers

[jackherer 543]

when u say 'it could be the diff', what exactly could it be?

 

I'm not sure tbh, but its often said that the diffs are weak spots on these gearboxes and every now and then someone posts a picture of a big hole in their diff casing.

 

Another thing that could be causing it is loose subframe bolts, even if they are only every so slightly loose they can clunk pretty badly.