Technical TA Noise when reversing

[tommus]

Hi

Had my car serviced for the first time last week and they told me it had an oil leak which it had to go back in for and also there was a noise coming from the clutch when reversing that needed no attention at this time (it was marked as amber on the servicing sheet). I hadn't really noticed it before as usually have my music on all the time but I went out, reversed and had a listen. There definitely is a noise. It's like a loud humming sound over the top of a normal reversing noise. Has anyone noticed this with theirs? Any ideas as to what it could be? Could the clutch be going?? I do notice the 'bite' isn't as strong as it used to be when pulling off.

Many thanks

 

[wellfan]

Hi

Had my car serviced for the first time last week and they told me it had an oil leak which it had to go back in for and also there was a noise coming from the clutch when reversing that needed no attention at this time (it was marked as amber on the servicing sheet). I hadn't really noticed it before as usually have my music on all the time but I went out, reversed and had a listen. There definitely is a noise. It's like a loud humming sound over the top of a normal reversing noise. Has anyone noticed this with theirs? Any ideas as to what it could be? Could the clutch be going?? I do notice the 'bite' isn't as strong as it used to be when pulling off.

Many thanks

I also have had this noise since I bought the TA in May. Did a search around on the net and seems to be a common issue. My neighbour is an engineer and tried to explain to me what the source of the noise is, something to do with how the gears are manufactured. Forward drive gears are syncromeshed, reverse gear is not. The shape of the shaft is what causes the noise. Just seems worse on the 500. I have had my fill of Fiat issues so have just decided to live with this one until I can be arsed taking it in for its first service.
No doubt a more knowledgeable member will be along shortly to explain in greater detail.

 

[TrevC]

Yep, my TA lounge does it, too, and so does my mate's Twinair. They've both done it from new. I'm regarding it as a characteristic rather than a fault (it hasn't got worse in 14500 miles) but I'll mention it when the car is serviced at 18000.

 

[Robnw67]

This information is taken from Wikipedia. Is this what you are describing?

"The implementation of the reverse gear is usually different, implemented in the following way to reduce the cost of the transmission. Reverse is also a pair of gears: one gear on the countershaft and one on the output shaft. However, whereas all the forward gears are always meshed together, there is a gap between the reverse gears. Moreover, they are both attached to their shafts: neither one rotates freely about the shaft. When reverse is selected a small gear, called an [ame="http://en.wikipedia.org/wiki/Idler_gear"]idler gear[/ame] or reverse idler, is slid between them. The idler has teeth which mesh with both gears, and thus it couples these gears together and reverses the direction of rotation without changing the gear ratio.
In other words, when reverse gear is selected, it is in fact actual gear teeth that are being meshed, with no aid from a synchronization mechanism. For this reason, the output shaft must not be rotating when reverse is selected: the car must be stopped. In order that reverse can be selected without grinding even if the input shaft is spinning inertially, there may be a mechanism to stop the input shaft from spinning. The driver brings the vehicle to a stop, and selects reverse. As that selection is made, some mechanism in the transmission stops the input shaft. Both gears are stopped and the idler can be inserted between them. There is a clear description of such a mechanism in the [ame="http://en.wikipedia.org/wiki/Honda_Civic"]Honda Civic[/ame] 1996-1998 Service Manual, which refers to it as a "noise reduction system":

Whenever the [ame="http://en.wikipedia.org/wiki/Automobile_pedal"]clutch pedal[/ame] is depressed to shift into reverse, the mainshaft continues to rotate because of its inertia. The resulting speed difference between mainshaft and reverse idler gear produces gear noise [grinding]. The reverse gear noise reduction system employs a cam plate which was added to the reverse shift holder. When shifting into reverse, the 5th/reverse shift piece, connected to the shift lever, rotates the cam plate. This causes the 5th synchro set to stop the rotating mainshaft.
—(13-4)
​

A reverse gear implemented this way makes a loud whining sound, which is not normally heard in the forward gears. The teeth on the forward gears of most consumer automobiles are helically cut. When [ame="http://en.wikipedia.org/wiki/Helical_gear"]helical gears[/ame] rotate, there is constant contact between gears, which results in quiet operation. In spite of all forward gears being always meshed, they do not make a sound that can be easily heard above the engine noise. By contrast, most reverse gears are [ame="http://en.wikipedia.org/wiki/Gear"]spur gears[/ame], meaning that they have straight teeth, in order to allow for the sliding engagement of the idler, which is difficult with helical gears. The teeth of spur gears clatter together when the gears spin, generating a characteristic whine."

 

[babbo_umbro]

It's very common for the transmission to make a different noise when reversing - there are more gears involved to change the direction of rotation and it also puts a different load on things like the differential bearings - the one thing that it doesn't do is make any difference to the clutch.

 

[bgunn]

He's saying clutch, not the actual gears. Incidentally, I get a bit of clutch squark from my 500 when slipping the clutch in reverse - nothing hellish though. Think it's a characteristic, as the clutch behaves perfectly normally in every other way..

 

[babbo_umbro]

He's saying clutch, not the actual gears. Incidentally, I get a bit of clutch squark from my 500 when slipping the clutch in reverse - nothing hellish though. Think it's a characteristic, as the clutch behaves perfectly normally in every other way..

I understand what he's saying - but can you explain what difference it makes to the clutch whether the car's going backwards or forwards? The different noise is either coming from a component that IS affected by the direction of travel - something in the transmission - or the way in which the clutch is being used - I know that I tend to slip the clutch much more when reversing as opposed to starting off forwards - which is what you also say, but I assume that the original question allowed for that as it's so obvious.

 

[dirtyhands]

the clutch will have no idea if you are going forward or reversing as the flywheel which clutch is bolted too can only travel in one direction,however foot will not be removed off pedal as you only maybe going back a metre or 2 ,revs can also have an effect on load and where your foot is on clutch pedal.gearboxes do sound different as less time is spent in reverse and more traveling forward.

 

[bgunn]

I understand what he's saying - but can you explain what difference it makes to the clutch whether the car's going backwards or forwards? The different noise is either coming from a component that IS affected by the direction of travel - something in the transmission - or the way in which the clutch is being used - I know that I tend to slip the clutch much more when reversing as opposed to starting off forwards - which is what you also say, but I assume that the original question allowed for that as it's so obvious.

Reverse gear ratio is quite high though, so there's more load on the clutch, which means it's more inclined to squark. Try pulling away in second gear, and I'll bet you can reproduce the noise in a forward direction - I can. Agree that you tend to slip the clutch more in reverse too..