No drive on a hill start/ Gearbox bangs into gear

My wifes 08 C3 has starting to play up, when stopped at a up hill junction and she goes to pull away it revs but no gear is selected then all of a sudden it bangs into gear and moves, any ideas what could be causing this?

Dmc68 wrote: ↑Fri Mar 05, 2021 2:29 pm My wifes 08 C3 has starting to play up, when stopped at a up hill junction and she goes to pull away it revs but no gear is selected then all of a sudden it bangs into gear and moves, any ideas what could be causing this?

Hi

The bang of a C3 auto is usually the valve. It will throw a 'fault code 6'

There is a topic about the valves that cause the AL4 to bang here

You may or may not get a warning on your central display and the computer might not log a fault code.

The AL4 auto box runs on very specific hydraulic pressures and these pressures are controlled by a modulator valve in the gearbox. Everything the gearbox does is run by these pressures so the modulator valve is very important.

Some people claim to have fixed gearbox problems by changing the transmission fluid. But 99% of the time the valve needs to be replaced.

The AL4 gearbox is fairly "popular" so most automatic transmission repairers are familiar with them.

Thanks for the replies, I tried to check the oil level but couldn't find anyway of doing it. the bolt on the underside released 800ml of oil then stopped. then there is another tube like screw with a hex head which I took out and that released the rest of the oil, which combined totalled approx 3.5 ltrs, which is what I put back in. The car ran fine on the 3 mile journey back home so the wife took to town which is approx 18 miles away and it started to play up again nearer to town, but ran fine when cooled down but statrted to play up again nearer home. It seems when up to temp it plays up. Did I put enough oil back in?

Dmc68 wrote: ↑Wed Mar 10, 2021 9:43 am which combined totalled approx 3.5 ltrs, which is what I put back in.

I assume you put new oil in and not the old oil in? (just checking).

Yes new oil. The old oil was black

Dmc68 wrote: ↑Wed Mar 10, 2021 12:36 pm Yes new oil. The old oil was black

Thanks


Black colour can come from the friction linings in the gearbox, as they wear excessively the bits end up in the oil. This gives the oil a dark colour, different shades of brown to show the wear of the gearbox.

Dmc68 wrote: ↑Wed Mar 10, 2021 9:43 am I tried to check the oil level but couldn't find anyway of doing it. the bolt on the underside released 800ml of oil then stopped. then there is another tube like screw with a hex head which I took out and that released the rest of the oil, which combined totalled approx 3.5 ltrs, which is what I put back in.

You may have this AL4 oil level checking system

Yep that's the one, so basically if I loosen number 3 and oil comes out the level is fine?

Dmc68 wrote: ↑Thu Mar 11, 2021 9:08 am Yep that's the one, so basically if I loosen number 3 and oil comes out the level is fine?

Not really totally correct

All you know it that the level is not too high, the same would result with a gearbox with no oil.


The idea is to over fill it slightly, and then to do the level checking by watching the small 'overflow' from the number 3.

If none comes out, top up a bit more and then release 3 again until there is a flow of oil out.

When the oil stops, its done.

A rather overly complicated system just to check an oil level