gearbox 'knocking' noise

gearbox 'knocking' noise

Author
Discussion

Lloyd551

Original Poster:

9 posts

21 months

Tuesday 15th May
quotequote all
Evening all

so my S2 has recently developed a knocking sound from the gearbox. however I have rebuilt the slave cyclinder over winter so have disturbed that general area.

the noise is constant with engine speed and goes when I have my foot on the clutch.
I'm thinking this could be the release bearing but not sure so thought i'd ask !

few questions: can i drive with this for a bit or is it best to take it off the road straight away ?
and whats the job like to fix, im assuming gearbox out. I know at least one of the ends of a spanner so would do it myself

cheers

phillpot

14,490 posts

119 months

Tuesday 15th May
quotequote all
Could it be a propshaft uj?

Lloyd551

Original Poster:

9 posts

21 months

Tuesday 15th May
quotequote all
even when the car is stationary ?

how would i check that ?

phillpot

14,490 posts

119 months

Tuesday 15th May
quotequote all
Lloyd551 said:
even when the car is stationary ?
Ah, missed the stationary bit.

Could well be the release bearing, perhaps you "disturbed" something when changing the slave cylinder?

time to pop the gearbox out scratchchin

Ralph S3

319 posts

189 months

Wednesday 16th May
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Are you sure its not just the push rod rattling when its not under load. When I did my slave cylinder last year I had a horrible rattle that increased with engine speed. Turned out the push rod was just loose enough when clutch not depressed that the rod and the clutch fork were able to vibrate. Easy to check, when you rev the engine just push a long/thin piece of wood against the clutch fork where it meets the push rod and see if noise stops. If it does, just make the push rod longer using the adjustment nut and take the slack out.

Ralph
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greymrj

2,956 posts

140 months

Wednesday 16th May
quotequote all
Might be a little difficult to be sure but is it a knocking noise at engine speed. The kind of noise that would arise if something is touching every turn of the engine? Or is it random?

Lloyd551

Original Poster:

9 posts

21 months

Wednesday 16th May
quotequote all
I'll get the car up and check the push rod see if i have any joy there

Its definitely not random, had the same symptoms every time the clutch isnt depressed. On start up and shut down

GreenV8S

26,349 posts

220 months

Wednesday 16th May
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To me the word 'knocking' suggests something much heavier than the rattle of a loose pushrod. Can you clarify what you're hearing?

Lloyd551

Original Poster:

9 posts

21 months

Wednesday 16th May
quotequote all
A medium - high frequency knocking sound coming from the gearbox. Changes up and down with engine speed, but as soon as my foot is fully depressed on the clutch it goes

greymrj

2,956 posts

140 months

Wednesday 16th May
quotequote all
Doesn't sound like the pushrod to me.
While you are underneath check the position and movement of the clutch release arm. You said you have had the slave out, did you by any chance manage to dislodge the clutch arm from the fulcrum on the other side of the box which could partially detach the release bearing.The clutch arm is a lever which should be fixed at the other side of the box. It should only be able to move forwards and backwards freely by a small amount. If the clutch arm can move in and out of the bellhousing, or is angled to the clutch, it is likely it has pulled out from the fulcrum pin.

Regrettably I cannot find a picture of the clutch arm fulcrum arrangement.

To be honest, if it has come out I dont know if it can be replaced because there are two tangs on the release bearing housing that have to engage correctly. Phillpot or Kitchski might know

GreenV8S

26,349 posts

220 months

Wednesday 16th May
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Does the front pulley move when you depress the clutch with the engine running?

Kitchski

6,004 posts

167 months

Wednesday 16th May
quotequote all
Do you need to depress the clutch pedal fully for the noise to go, or does it disappear the instant you put any weight on the clutch pedal at all?

Lloyd551

Original Poster:

9 posts

21 months

Wednesday 16th May
quotequote all
Thanks greymrj, i'll get the car up on ramps either tomorrow or Friday and check those things. I did try my best to not disturb anything, maybe not careful enough ...

i'll go out now and check the front pulley and post the results

yes I need to fully depress the clutch pedal, if I half depress it the noise is still there

greymrj

2,956 posts

140 months

Wednesday 16th May
quotequote all
GreenV8S said:
Does the front pulley move when you depress the clutch with the engine running?
Yes that would be bad news. It is however a Cologne and the thrust 'washers' are integral with centre main shells so it would be unlikely, I cant remember hearing of a thrust washer failure on an S?

Lloyd551

Original Poster:

9 posts

21 months

Wednesday 16th May
quotequote all
Had a look at the front pulley while running and it doesnt move at all. Is that good news ?

GreenV8S

26,349 posts

220 months

Thursday 17th May
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Yes, it confirms the problem is on the gearbox side of the clutch.

greymrj

2,956 posts

140 months

Thursday 17th May
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Lloyd551 said:
Had a look at the front pulley while running and it doesnt move at all. Is that good news ?
Very much so!. In the engine there are thrust bearings, every time you change gear there is a thrust along the crankshaft. Those 'bearings' are there to resist that. If one fails the crank can start to move forward and backwards. That very rapidly becomes serious and often creates terminal damage. In the Cologne engine those 'bearings' (they are flat white metal) are pretty big and well located and I dont remember hearing of them failing.
If the crank isn't moving the problem is definitely with the clutch area. Lets see what you find out from the clutch arm.

If you haven't already got one, you must get a copy of the Haynes manual for the 2.9V6 Ford Sierra or Granada, cheap enough on ebay. I think you are going to need it.

Kitchski

6,004 posts

167 months

Thursday 17th May
quotequote all
Lloyd551 said:
Thanks greymrj, i'll get the car up on ramps either tomorrow or Friday and check those things. I did try my best to not disturb anything, maybe not careful enough ...

i'll go out now and check the front pulley and post the results

yes I need to fully depress the clutch pedal, if I half depress it the noise is still there
Gearbox is the most likely culprit then, I'm afraid. You could try putting some proper gearbox oil in it though; the Type 9 used EP80 originally, but after owners of new Capris complained of a reluctant gearshift when the car was cold, Ford 'sorted' the problem by filling them with ATF instead. ATF, as a manual gear oil, is crap. I run 75w90 in mine, and advise most to do the same. The gearshift is still fine when cold, too!

The only problem is that you can't drain the oil unless you tip the gearbox upside down (because in Ford's infinite wisdom, they didn't fit a drain plug), so to change it you'd effectively have to syhpon the oil out through the filler hole. Obviously that won't get all the ATF out, so you'll need to do that a few times over the course of a few months to convert it as best you can. I keep meaning to check whether ATF will settle on top or underneath gear oil, or whether they'll mix. If it sits on the top - result!

Another thing to check is that it hasn't been leaking oil through the inspection cover at the top. I've never seen it personally, but I've heard this was a problem on the earlier boxes, and that they'd eventually run out of oil!

greymrj

2,956 posts

140 months

Thursday 17th May
quotequote all
Kitchski said:
Gearbox is the most likely culprit then, I'm afraid.
I am puzzled though Richard. This happened after a slave cylinder replacement. How could that lead to a 'knock'. Surely it isnt likely to be in the gearbox itself. Lets see what is found when the clutch arm is checked. Shame neither of us can see and listen, we could track it down easily. Up on a ramp with the old screwdriver or pipe to the ear? I am going to stick my neck out, clutch arm has become disengaged and is clunking as the thrust race turns!! Lets see if I need to change the crystal ball!!!

Kitchski

6,004 posts

167 months

Thursday 17th May
quotequote all
greymrj said:
Kitchski said:
Gearbox is the most likely culprit then, I'm afraid.
I am puzzled though Richard. This happened after a slave cylinder replacement. How could that lead to a 'knock'. Surely it isnt likely to be in the gearbox itself. Lets see what is found when the clutch arm is checked. Shame neither of us can see and listen, we could track it down easily. Up on a ramp with the old screwdriver or pipe to the ear? I am going to stick my neck out, clutch arm has become disengaged and is clunking as the thrust race turns!! Lets see if I need to change the crystal ball!!!
Could just be a coincidence that the noise appeared after the slave was done. The only other possibility is that the dust plate is rubbing something, but normally that causes a noise when you push the clutch, not release it.

Normally, if the noise changes or goes away when you put weight on the clutch pedal, it's release bearing/arm related, as the weight of your foot takes up any free play (or loads up a noisy release bearing to the point it shuts it up temporarily). If you have to put your foot on the clutch and push it down to get the noise to stop, this suggests it's gearbox related, as the input shaft is the only thing that stops spinning (the clutch plate does too, but when it was spinning it was strictly in sync with everything that surrounded it.

I mean I could be wrong, but in my mind it's got to be something after the clutch for the noise to be affected the way it is.