Technical Gearbox chatter

[jorgy]

Hello all Xers.
My 78 X1/9 has a chattering sound at idle coming from the gearbox. It goes when I move the gearshift slightly towards 1st or 3rd gates.
Is this a common problem?
Is it easily repaired / adjusted?
....or is it something more insidious???

Any advice would be greatly appreciated.

 

[RS Pilot]

What happens if you press down the clutch (and don't touch the gear lever)?

 

[jorgy]

What happens if you press down the clutch (and don't touch the gear lever)?

No change RS PILOT. Are you thinking thrust/throwout bearing
Steve C thinks might just be wrong g/box oil.
Fingers crossed! Hope so!
Thanks for reply.

 

[RS Pilot]

No, I was thinking it was just the input shaft rotating with non engaged gears. I have a 4-1 on my exy so wouldn't be able to tell if mine was rattling or not but I have had a Peugeot where the input shaft rattled until you depressed the clutch and that was considered normal.

If the rattling is still there with the clutch depressed I don't think it will be the oil as there's nothing in there rotating at all (providing the car is stationary).

If the noise is definately coming from the gearbox (rather than the linkage) it must be to do with the selector forks. I'll have a look at the schematic in the Haynes later and see if anything obvious jumps out.

 

[fiatfactory]

If the noise DOESN'T go away when the clutch is depressed then you may indeed have a different problem.... I thought the chatter you were refering to was the slight rumbling sound that the gearbox usually makes when idling in neutral and the clutch pedal is untouched (and hence the clutch is engaged, and the input shaft of the gearbox is spinning) ...... if the clutch pedal is depressed, then the clutch disengages the input shaft from the drive of the crankshaft, and given a moment will slow down and stop.... so any noise that could be attributed to the insides of the gearbox should cease..... your problem could well be the clutch release bearing constantly touching the diaphragm fingers of the pressure plate and making noise (probably due to incorrect adjustment if the noise is constantly there)

but you probably have the wrong gearbox oil as well.... about 8 out of 10 X19's I see have EP oil in the gearbox which is incorrect and will lead to another set of problems.

SteveC

 

[alexGS]

Excellent answer SteveC - particularly on the point of the EP oil. It's a distinctive smell when you drain the gearbox oil. I like to fill up with engine oil, add some engine flush, go for a drive, then drain before refilling with the correct non-EP oil. I use Castrol VMX in other people's cars (or FIAT ZC90 in my own cars!)

I had an Uno gearbox once that made a horrible noise when idling. The engine also idled roughly, so that was probably a contributing cause. We (myself and a FIAT specialist) took the gearbox apart and replaced $350-worth of bearings (all the races were 'peppered'.) Put it up together and... no difference!

I have since begun to wonder if perhaps the clutch release bearing could rattle on the fork as well. This doesn't happen in the Uno because the bearing is spring-loaded against the diaphragm fingers (constant contact) - the pedal is pulled down by a spring.

But I think it's pretty certain that the synchro sliders etc. all rattle merrily on the first shaft... and that is what makes the noise. My X1/9 has only 76,000km on the clock, so perhaps its sliders are less worn - it doesn't rattle!Thicker gearbox oil may help - otherwise, you just have to ignore it (it doesn't affect how well the gearbox works, after all).

Castrol VMX claims to "reduce hot idle rattle". I've found that having the gearbox topped up to the maximum also helps.

-Alex