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[jerry]

Hi
Yet more problems with friends car that maybe someone can help with? She has a pt cruiser auto and whist it drives fine in all other gears it doesnt in reverse. Simply put it in reverse and it will creep back as it should, but as soon as she touches the accelerator the car just revs like mad but just continues to creep back in reverse at the same pace as before. Any ideas?
                                                                                                                            cheers
                                                                                                                            jerry

[Marks DTM Calib]

Dont like the sound of that and the chrysler boxes on those are not recognised for thier reliability (although the usual failure mode is compelte failure!).

Assuming its ok in all forward gears then I would guess that that the reverse gear brake band or associated actuators are goosed.

[jerry]

Cheers Mark,
Bit bizarre though. Im in no way mechanically minded, but surely it must " go into" reverse gear in order to creep backwards in the first place? Is it the "brake band " you mention that is then working against the accelerator ? I assume that this "brake" should be disengaged and its not? 

[aaronjb]

The brake bands 'lock up' parts of the transmission's gearset to create the desired ratio for any selected gear - if you want your mind blown (unless you happen to have one of 'those' minds that just gets it), read this on how an automatic transmission works, specifically the part about the planetary gear sets: http://auto.howstuffworks.com/automatic-transmission.htm

Essentially it sounds like the brake band(s) in question can't lock up the right parts of the gearbox when the input torque is greater than it is at idle, and the planetary sets just 'freewheel' - either because the bands are worn or the hydraulic actuators can't apply enough force to them due to stuck/gummed/failed solenoids etc.

[jerry]

The brake bands 'lock up' parts of the transmission's gearset to create the desired ratio for any selected gear - if you want your mind blown (unless you happen to have one of 'those' minds that just gets it), read this on how an automatic transmission works, specifically the part about the planetary gear sets: http://auto.howstuffworks.com/automatic-transmission.htm

Essentially it sounds like the brake band(s) in question can't lock up the right parts of the gearbox when the input torque is greater than it is at idle, and the planetary sets just 'freewheel' - either because the bands are worn or the hydraulic actuators can't apply enough force to them due to stuck/gummed/failed solenoids etc.

oh, I see, all makes sense now .
Seriously though, thanks for the explanation and link-I sort of get it now. Sadly methinks this could prove expensive, guess she'll have to remain carefull about where she parks! Cheers guys

[STMO123]

Judt leave it. As long as it goes backwards, albeit at a sedate pace. Probably best for a woman.