Automatic transmission problems

[TDG]

Over the last few weeks, I've been having some transmission problems which have culminated in the car becoming undriveable today.

Ever since I first bought the car a few months ago, I'd been having some rough gear changes and been planning to replace the transmission fluid sooner rather than later.

A few weeks ago, I began to get some flaring on gear changes. On the 2-3 change, I'd get an increase of a few hundred RPM during most gear changes. Under stronger acceleration and going up hills, there would sometimes be a dramatic increase of 3,000 RPM for a second or two during shifts into the higher gears before dropping back to a more normal level. Under lighter acceleration and on flats, no such problem occurred.

A couple of weeks ago, I changed the transmission fluid, hoping this would resolve the problem. Gearshifts were certainly smoother after the change, but the flaring was still occurring. (And, yes, I did follow the specified procedure and use a transmission fluid that was designed for the JATCO box)

I'd been planning to check the solenoids after work today, but hit serious troubles on the way to work. I first noticed surging on a 3-4 shift under light acceleration, then a couple of minutes later the car began to drive roughly as I was approaching a red light. When stopped at the lights, I switched off the engine and started it again - all seemed fine, but when the light turned green the car wouldn't move. For several minutes, I was stuck at the lights, continually restarting the car as I couldn't get any gear to engage.

Eventually, I got it into drive and it quickly switched into EP mode. This got me through the intersection and allowed me to take the first turn off the highway into a carpark. I then lost drive again in the carpark entrance. It then took several restarts of the car to make it into a park - each time it would hold gear for a period (and sometimes could be changed between drive and reverse a few times) and then lose all drive again.

I have since checked the resistance of the solenoids - all are in the standard range. It seems the car will now have to be left in the carpark until I can get it towed to a transmission specialist on Monday.

Any help with diagnosing this problem would be most appreciated.

I know some of the symptoms would seem to fit with cracking of the reverse piston, but does this normally lead to complete loss of both forward and reverse gears like this?

[TDG]

I should probably add that apart from the short period in 'EP' mode, I've been getting no warning messages at all. The IPK indicates the car is in a gear, but when I push the accelerator there is often no motion forwards or backwards at all.

[SD1too]

Originally Posted by TDG

I know some of the symptoms would seem to fit with cracking of the reverse piston, but does this normally lead to complete loss of both forward and reverse gears like this?

I believe that it can Tim, yes. Certainly forward gears can be affected as internal fluid pressure reduces due to leakage through the cracked reverse piston.

There are some excellent pictorial guides showing how this piston can be replaced by the uprated part without removing the transmission from the car (notably by rrobson and this thread by Oxygen.). The next best option is to get your specialist to remove the entire gearbox for standard reconditioning. If you're offered a "known good" gearbox at a bargain price, be careful! It's probably from a scrapped car and comes with no history or guarantee. One forum member chose to do this and ended up with a gearbox with different faults.

Simon

[mh007]

I also agree that this sounds like a classic Reverse Piston fault.

Despite its name, a fractured piston will have an effect on the entire gear range eventually.

Good advice about a used gearbox from SD1too.

[SD1too]

Originally Posted by mh007

Good advice about a used gearbox from SD1too.

Thanks Mike.

Simon

[TDG]

Thanks, Mike and Simon, for your help with this.

I suppose I can do now is try to find someone who is willing to investigate the possibility of reverse piston problems rather simply insist on a new gearbox.

I'll let you know how things go.

[TDG]

As suspected, it turned out to be a cracked reverse piston.

I found a local transmission specialist who was happy to investigate this possibility and soon after got a call confirming they'd opened the box in situ and found the piston cracked. They also found the clutch plates were worn, so replaced the steel and friction plates.

Now with my wallet a bit lighter (although not disastrously so), the car is once again running smoothly.

Thanks again for your help with this!

[beinet1]

Originally Posted by TDG

As suspected, it turned out to be a cracked reverse piston.

I found a local transmission specialist who was happy to investigate this possibility and soon after got a call confirming they'd opened the box in situ and found the piston cracked. They also found the clutch plates were worn, so replaced the steel and friction plates.

Now with my wallet a bit lighter (although not disastrously so), the car is once again running smoothly.

Thanks again for your help with this!

Thanks for the update! Nice to read that you got it sorted.

[stevenicks]

I just love a happy ending

[TDG]

A happy ending is certainly very welcome after having that sinking feeling that inevitably follows transmission failure for a couple of days!