You have not mentioned how many miles the gearbox has done, which may give readers a helpful clue! You should contact a member of the Federation of Automatic Transmission Engineers whom you can expect to give a good diagnosis of what is wrong. It may be that the auto gearbox requires a service (every 50k miles). This is recommended and involves cleaning the filter, where possible and (part) changing the fluid.

Car manufacturers rarely "recommend" that an automatic transmission needs "servicing" - other than the fluid change interval which varies very considerably, from 36,000 to 160,000 miles on the few cars that I've had - so "50k miles" shouldn't be taken as any sort of standard. Few modern automatics have external filters, most have internal ones that can only be reached by an expensive strip-down.

On reflection, Fernando P's post reads like an advert - I wonder who for?

Edited by RT on 16/10/2013 at 17:14

I wonder how you managed to interpret from my post that car manufacturers "recommend" that an automatic transmission needs servicing?

You posted this:-

"It may be that the auto gearbox requires a service (every 50k miles). This is recommended....."

It's the car manufacturer that specifies, ie recommends, the service schedule.

Edited by RT on 16/10/2013 at 18:51