Very strange gearbox noise

[adurer]

Hello friends

Today I would like to ask your opinion about a strange noise coming from inside the gearbox.

Here are some details about that noise

• it sounds like a foreign object moving randomly inside gearbox
  
• it is located on the wheel side, not on the clutch side of the gearbox (I used a stethoscope)
  
• it can be heard very clearly only when the engine is cold (i.e. first start in the morning). The noise disappears when the engine (gearbox?) gets warm
  
• if I depress the clutch pedal, the noise will go away
  
• other than that, the gearbox works nicely, smooth shifting, no other noises whatsoever
  

I am very worried something might seize while driving and I need your advice.

[Lee A]

Hello friends

Today I would like to ask your opinion about a strange noise coming from inside the gearbox.

Here are some details about that noise

• it sounds like a foreign object moving randomly inside gearbox
  
• it is located on the wheel side, not on the clutch side of the gearbox (I used a stethoscope)
  
• it can be heard very clearly only when the engine is cold (i.e. first start in the morning). The noise disappears when the engine (gearbox?) gets warm
  
• if I depress the clutch pedal, the noise will go away
  
• other than that, the gearbox works nicely, smooth shifting, no other noises whatsoever
  

I am very worried something might seize while driving and I need your advice.

Hi,

I recently noticed that noise on my felly and it would go away when I depress the clutch from idling.

I just put it down to age and live with it, it's not overly annoying and as long as it still works I'm not complaining lol

Lee.

[djaychela]

Does it make this sound only when you are stationary, or also when on the move? Are there any other noises?

[Lee A]

Does it make this sound only when you are stationary, or also when on the move? Are there any other noises?

For me personally i only notice it idling... Asked my ex mechanic dad and he said its just one of those things with FWD and rattling boxes

Lee.

[adurer]

Does it make this sound only when you are stationary, or also when on the move? Are there any other noises?

It makes the sound also on the move, but as I said, only when the gearbox is cold, usually some 5 minutes.

I didn't notice any other noise. If you are thinking at that 5th gear noise... no, it is not there, gearbox is very quiet.

I am fearing the most some debris that might get stuck in between gears. I don't know if there is a magnet on the bottom to collect them. But then I think myself... the noise is not traveling all over, and it stops when depressing the clutch, stationary or on the move.

To me it looks related to input shaft. But that is theory and I am not a specialist.

[djaychela]

I would definitely say it was input shaft-related; it has tapered bearings on there which have to be set precisely and if not the gearbox will be noisy (I've built a few, and also made some mistakes!). If it only does it when it's cold it does sound like that, and when it warms up the clearances are changing. The problem is that the only way to be sure is to remove and strip the gearbox.

There is a magnet inside the gearbox case to collect debris; it is not accessible without stripping the gearbox (it is by the differential, seen oh the extreme left of the your picture).

[adurer]

Thank you for clearing this up. Two things still need to know.

1. Is there any immediate danger?

2. How precisely have to be set those bearings? What mistake could I fall in?

[Guest masster]

adurer

if you remove the gearbox and take it apart, it is a good idea to be very methodical, measure existing clearances prior disassembly, and definitely take some photos or record a movie.

we surely need such photos too, I don't know of any existing on the net for Felicia gearbox.

it is very important to have a good press for bearings and avoid hitting anything with a metal hammer.

Edited 15 August, 2012 by masster

[adurer]

I would certainly need too photos or movies from a Felicia box overhaul.

But they are not available. I feel myself able to take gearbox out, but when it comes to anything that needs to be removed/fitted by extraction/pressing... I am afraid to break something or not mount it like factory did.

Perhaps I have to see at least a video of a similar transaxle box first.

[djaychela]

You can dismantle the gearbox with only standard workshop tools. You won't need a press to service the input shaft, you can remove the bearings and the races with a hammer and drift or a small puller for the bearings (I did mine without, several times). The input shaft bearing clearance needs to be very small (around 0.01mm) which is easily measured using a DTI with the box being dummy-built. I had to make a shim up for mine when I fitted the new gearset, easily made from shim steel using scissors. The diff bearings are similar - the Skoda workshop manual shows a tool set for spacing the gearbox cases apart and then allowing measurements to be made, but it's quite possible to do it without them and with careful measurement. The diff bearings are an odd size but any large bearing shop will have them. The input shaft bearings are common, off the shelf items. The intermediate shaft bearings are both bespoke, but I've never had any trouble with them on any of my boxes; the outer one is easily replaced, but the inner (engine end) one is less so, but not impossible. The most difficult part is assembling the cluster into the box, but once you've done it a couple of times it's easy.

In response to your original question, there's no way to tell if there's immediate danger - it could be anything that's wrong, and without taking it apart, it's almost impossible to know.

[adurer]

In response to your original question, there's no way to tell if there's immediate danger - it could be anything that's wrong, and without taking it apart, it's almost impossible to know.

Thank you again for all information. They are very helpful. I will definitely take the gearbox apart in late September. I understand there could be anything inside and can't tell for sure what and when will seize, but assuming that only input shaft bearings are worn, have you heard of any such bearing break while driving, or block and tear apart all gears? That's my darkest scenario, although 1) I don't carry any loads with my car, and 2) those bearings 'swim' in oil...

On the other hand, I will do my best to document the entire procedure and then I will post detail photos with my findings to decide (with your help) what to replace.

Edited 16 August, 2012 by adurer

[djaychela]

No problem.

There are (not great) scans of the workshop manual for the Favorit box (which is the same as the early Felicia one and very similar to the later Felicia one) here:

http://darrenjones.is-a-geek.com/~darren/pics/gearbox/

It details the shimming procedure but as I said above, you can do without the special tools if you make careful measurements using a DTI.

I've not heard of a gearbox failing in the manner you describe, providing everything is bolted up. Worst I ever managed was to kill 2nd gear on a rally completely (in my Favorit), and had to drive it home unable to select 2nd at all, going from 1st to 3rd; made the 100 miles home "interesting", but it didn't let us down...

[adurer]

I didn't know that Favorit gearbox is identical with pre-1997 Felicia. I was expecting to be a VW clone.

Thanks for useful documentation from your site :clap: .

What is the exact name and author of that book please?

Is it Skoda Favorit Owner's Workshop Manual by Andrew Hamlin published by Haynes?

Edited 17 August, 2012 by adurer

[adurer]

Should I replace input shaft bearings with new, original, exact code ones, new shimming is mandatory?

I mean, are the manufacturing tolerances so big they exceed mounting clearance precision?

[Guest masster]

the pages scanned from (probably) from Haynes favorit state:

- Should the outer ring of the input shaft bearing and the outer ring of the differential be removed out of the gear box, mark and store the shims which the input shaft bearing is supported with (the bearing axial clearance is stated) and

the shims as well, which the differential bearing is supported with (bearing preload is stated).

- Should the housing, the differential or its bearings, the input shaft or its bearings not be changed, and was the gearing not noisy before assembly, remove the shims and store them in the same order they were used in in order to use them

again — you save a complicated measurement and finding rhe shims.

so it appears that new bearings = new shims

[djaychela]

Shimming is indeed mandatory. Tapered bearings, etc...

[spoil_kid123]

Do you have a better scan of the Felicia Gearbox repair procedure.

[djaychela]

Sorry, that's the only ones I have. Everything is readable on it though? What's the problem?

[adurer]

I've talked with a Czech mechanic and he is 99% sure the noise is due to input shaft end nut got loose. He referred to that M22x1.5 nut that holds 5th gear in place (see photo). Is that plausible? Because I got that noise for over a year now and I assume the nut would be unscrewed by now. Or it doesn't have enough room to get out?

Anyway, if that's the case, I will buy a new nut. But how much do I have to tighten that nut before securing it?

Edited 12 February, 2013 by adurer

[Dost]

Hi,

I recently noticed that noise on my felly and it would go away when I depress the clutch from idling.

I just put it down to age and live with it, it's not overly annoying and as long as it still works I'm not complaining lol

Lee.

Bro if im not wrong u need to change the flywheel assembly, My Skoda Laura L&K had the same problem but after i changed the Flywheel Assembly the noise disappeared.. Hope this will solve ur problem too... Cheers!!

[dohnjoe]

you're wrong.
different cars with different weaknesses.
different noise locations.
etc etc
I explained everything in this post.

[RicardoM]

A fellow member from Egypt had this noise too but after changing the clutch kit the rattling noise stopped. The culprit seems to have been the clutch release bearing - CRB for short (see photo). The noise resembled most with a worn bearing. But that looks odd to me. CBR spins only when the clutch pedal is pressed. Yet the rattling noise could be heard only when the clutch pedal is not pressed   How could that be?? What do you think?

 

 

Here is a video showing how to pinpoint the source of the noise. The noise is louder at gearbox mounting point and almost non existent at clutch housing.

 

Edited 2 November, 2015 by RicardoM

[RicardoM]

Having my gearbox disassembled I've addressed this issue too. The faulty parts are the tapered roller bearings of the input shaft.

 

Part numbers are:

963020597 (30205AC6 manufacturer code)

963200599 (32005AXC6 manufacturer code)

[RicardoM]

 

Photos of the input shaft bearings.

 

I've changed the bearings of the output shaft too, just to be sure.

969002515 (PLC 05-12 manufacturer code)

002311139 (PLC 44-17 manufacturer code)

[Anthony96]

Someone told me is my needle bearing wen i start the car it makes a rattling noice an when i mash the clutch the noise goes away it also goes away when the car gets hot any suggestions the only bearing i getting in my County is the clutch release bearing