Knock When Moving Off

[veedubnoodle]

More noises.

A fairly loud continuous knock that gets louder/faster the faster you go- slows right down when moving slowly. It pretty much disappears under heavy braking and accelerating, and is loudest when you lift your fit off the accelerator.

I should add that the car is booked in next week, so I'm not after an Internet diagnose as I appreciate it could be anything. Knowing nothing about mechanical bits, I'm just curious as to what it may be.

Sounds like it could be an inner CV Joint...

 

[Lyons]

Would that ease when accelerating and worsen lifting off? What role do they play/how do they physically work?

 

[Coog]

Yeah it can do. We nursed a scallyrally car round Ireland with a knackered driveshaft and the only way to silence it was to nail it in 3rd and/or stand on the brakes. Cruising about it made an absolute racket.

I put a few CV's through my own GTI over the years though mine never knocked, just a bit of a rumble when turning.

 

[Ian A]

Thought inner CV too.

As the drive is re-engaging power through it, it would maybe stop any knocking. Then once you let off, it ticks in its housing.

Probably be at its worse in neutral with no drive at all.

 

[Lyons]

Doesn't do it at all when stationary, will try it in neutral on the way home.

Cheers for that description Ian.

I thought perhaps driveshaft, but I have absolutely no clue what I'm talking about .

 

[Ian A]

Check under the car to see if the inner CV boots are split.

 

[veedubnoodle]

Inner CV Joint is part of the driveshaft. It basically allows to shaft to move about at various angles (when turning or under compression). If the joint is broken the bearings inside will move about causing a rumble / knocking / clicking depending on the severity of the joint failure.

So under load (accelerating or heavy braking) the bearings you see there will be held under pressure and not move around hence the lack of noise.

Hope this helps

Edit: It may also be an outer joint that has failed but generally they click instead of rumble or knock

 

[Ian A]

Must be all that wheel spinning your doing Ian

 

[Lyons]

Very interesting, thanks! Fingers crossed that's all it is .

 

[Lyons]

Out of curiosity, would it be advisable not to do too much driving if it is the cv joint?! Just dawned on me that I've been driving away at it for over a week and have to head up to the airport again tomorrow too.

 

[johnm]

I'd be another one for the inner CV joint, does it only do it after a certain amount of miles?
My Legacy did it and got really loud after around 40miles, after getting down and looking underneath and proding about, turned out it was the inner cv joint, replaced it and no more knocking.

 

[veedubnoodle]

Out of curiosity, would it be advisable not to do too much driving if it is the cv joint?! Just dawned on me that I've been driving away at it for over a week and have to head up to the airport again tomorrow too.

Yeah mate, I wouldn't be doing too much driving on that.

I had a outer CV Joint clicking on my old Passat a few years ago and I drove it on for a week until I had the free time to change it. Parking in the car park of work it went bang (had to abandon the car parked fully sideways cause it wouldn't move) and I had to get it recovered to the garage to change it. That was me driving easy to and from work (only 4 miles each way) and it didn't last a week.

 

[pablo]

did you look at the boots yet? should be obvious if split.

if getting a new joint get a genuine one, the aftermarket ones are usually crap.

 

[greyfloppyhat]

did you look at the boots yet? should be obvious if split.

if getting a new joint get a genuine one, the aftermarket ones are usually crap.

I've found J&R's to be very good, I would tend to just swap the whole drive shaft as it's not much more than changing the other / inner and saves me some hassle.

But maybe I've just been lucky with J&R

 

[pablo]

my experience actually comes from a J&R shaft on a GTTDI golf. was knocking again in a couple of weeks. replaced it with a good second hand oem shaft and all better.

 

[Coog]

Any time I've used J&R they've been terrible. Twice and both times the stuff was junk. Lesson learned.

 

[pablo]

maybe ok on a petrol car but a torquey derv needs good driveshafts.

 

[Lyons]

Haven't had a chance to look yet. I'll be honest in that I'm not hopeful that I would even know what to look for.

I take it a CV joint would be beyond the ability of an amateur? Bearing in mind I thought a back box was a cat .

 

[pablo]

look underneath (prob dont need to jack it) and see if there is grease splattered round any of the 4 boots. will be real obvious as it goes everywhere when the boot splits.

not the handiest job to be fair but should be cheap for a mechanic to do it with the right tools etc.

 

[greyfloppyhat]

my experience actually comes from a J&R shaft on a GTTDI golf. was knocking again in a couple of weeks. replaced it with a good second hand oem shaft and all better.

Any time I've used J&R they've been terrible. Twice and both times the stuff was junk. Lesson learned.

Sounds like I got lucky I'll bear this in mind if I ever need to a drive shaft again, breakers it will be !

 

[Coog]

maybe ok on a petrol car but a torquey derv needs good driveshafts.

Mine weren't machined properly which meant that after a week or so the seals started to leak and it dropped it's gearbox oil all over the driveway.

 

[Ian A]

Haven't had a chance to look yet. I'll be honest in that I'm not hopeful that I would even know what to look for.

I take it a CV joint would be beyond the ability of an amateur? Bearing in mind I thought a back box was a cat .

If you could change your suspension yourself, you could probably tackle this. You'll need splines, loads of WD40 and a big hammer.

I had to put a shaft in my golf before it sold, straight forward enough, if a bit fiddly.

 

[pablo]

and a big 32?mm socket and bar for the hub end. a lump hammer will help too

 

[Steve]

Any time I've used J&R they've been terrible. Twice and both times the stuff was junk. Lesson learned.

Used them once for a shaft for the civic years ago, it lasted all my ownership and the next guys. Maybe just lucky..

 

[Coog]

Yeah you must have lol. I ordered a pair of driveshaft nuts off them for the MX5 (giving them the benefit of the doubt) and the nuts that arrived didn't look beefy enough and I wouldn't have trusted them. Plus they were entirely the wrong size. Off to Mazda for a couple of new ones.

In fairness they refunded me for them no problem.