How does automatic transmission works?

[sherifsaleh]

Hello everyone,

I need some help. I want to know how does the automatic transmission works and especially how it shifts the gear down/reduce speed.

As I have a noise only when I take my feet off the pedals which disappears if I press fuell again? I doesn't matter which speed I am on and it sounds mostly like two peices of metal rubbing agaisnt each other.

Thanks.

Sherif

 

[television]

Hello everyone,

I need some help. I want to know how does the automatic transmission works and especially how it shifts the gear down/reduce speed.

As I have a noise only when I take my feet off the pedals which disappears if I press fuell again? I doesn't matter which speed I am on and it sounds mostly like two peices of metal rubbing agaisnt each other.

Thanks.

Sherif

I think that if you Google your question you can sift through the 500 different answers.
Are you sure that this noise is comming from the box and not the rear end of the car.

Malcolm

 

[Rory]

Try here:
http://auto.howstuffworks.com/automatic-transmission.htm

 

[Dieselman]

What makes you think it's the gearbox, is it only when in one gear?

If it's every gear then I would suspect something like a mounting, either engine or gearbox mounts, or even a worn differential or gearbox bearing.

An auto box has a set of planetary gears which either lock the inside planets or the outside of the holding ring depending on which ratio is required. There will be two or three sets of these gears to provide all the required ratios.

 

[sherifsaleh]

Thanks. I am not sure the noise is form the gearbox but it only happens when I take my foot off the pedal and disappears when I accelerate again.

 

[Dieselman]

More like a mounting or the diff then.

 

[sherifsaleh]

Thanks again. How would I know whether it is the mounting or diff?

 

[BonzoDog]

http://en.wikipedia.org/wiki/Automatic_transmission

You will be tested later.

 

[television]

It could be a CAT rattling if it is only there when accelerating or pulling.

Malcolm

 

[grober]

transmisssion.

Reading your previous thread it sounds that you still have the same problem. Its almost certainly transmission related. Probably NOT the gearbox itself but more likely one of the following the propeller shaft, propeller shaft-centre bearing or its flexible mounting, the flexible disc couplings, the differential or its mountings, or rear half shafts .
Check the rear differential oil level and for signs of leaks. Remove the catalytic converter heat shield and check the centre differential bearing for play or wear. give it a good pull about-twist it back and forth You are looking for excessive play in any of these components. Under "DRIVE"=ACCELERATION this play/wear is taken up so you dont hear a noise. When you lift off the accelerator the transmission "unwinds" and any play or loose components can move about/vibrate and cause the noise you are hearing. If you are not comfortable doing DIY take the car to a good independent mercedes specialist or garage you trust and get them to check it over. If its any of the above faults most competent garages will be able to repair it. Its not something that requires an expensive official mercedes agent repair.