Clunks in the drivetrain after manual conversion

[C0V3R]

A bit of history - my c4 setup always used to clunk when going from reverse to drive when the drivetrain loaded up. My diff was slowly developing a slight whine on the hwy too.

Now I have converted to a manual (tko600) with a new driveshaft, unis, etc, and I am getting a lot of clunks when I change the loading in the car. For example, if I load it up heavily in thirds, let off the throttle quickly I will get a nice decent sounding clunk. I can feel the clunk in the shifter when I do it.

Is my diff on its last legs? What exactly sounds like its the problem? Too much backlash or just a worn out set of gears? Whats the easiest way to fix it?

 

[Ronstang]

It sounds like you have too much backlash in the gearset. That does not necessarily mean the gears are toast but that they might need some adjustments. An inspection of the carrier assembly should tell you what you are dealing with. If you need to only adjust the backlash then move the bearing adjusting cups the same amount to move the ring gear into the pinion and check with a dial indicator. Remember that you always want to tighten the bearing last so loosen the one that is moving out and then tighten the one that is going in.

 

[C0V3R]

I've swapped out the rear for a 3.55 rear (swapped the whole chunk) and the clunking is still there. I'm now pretty sure its not the diff.

I had a look at the motor mounts (less than 1 yr old) and one looked like it might have been cracked - could that be causing it? How can you tell if the mount is shot short of pulling it out of the car?

 

[C0V3R]

http://www.youtube.com/watch?v=aqnbEiv1y5M

This is a video with the gearbox in neutral with the wheels on the ground and handbrake on. Is this amount of movement & noise normal?

 

[65fastbackresto]

Sounds alot like a u-joint

Pretty sure it aint though, you wouldn`t have changed a chunk without checking the joints.

 

[ron67fb]

if I load it up heavily in thirds, let off the throttle quickly I will get a nice decent sounding clunk. I can feel the clunk in the shifter when I do it.

That sounds like a motor and/or trans mount issue. Turn on the engine, put the e-brake on and try to move the car forward in first gear while someone watches the engine. If it's the motor mount, the engine will move quite a bit towards the passenger side, and "clunk" as it settles back into place when you let off the clutch.

 

[ron67fb]

oops

 

[C0V3R]

Pretty sure it aint though, you wouldn`t have changed a chunk without checking the joints.

You're right - the driveshaft and U joints are all brand new.

I changed the chunk because the old one was whining a bit and so I could get a better match to my overdrive gear.