Trouble with gearbox, un-drivable at the moment

[1pk]

I drove to work today, parked and plugged in as I always do. When I left at the end of the day the car was slow to move, it seemed like the e-brake was still on but it wasn't. I pressed harder on the accelerator and it lurched repeatedly as it moved forward almost like something in the gearbox was catching and then releasing. I knew this wasn't good and not wanting to drive anymore I put it in N to see if I could push it back into the parking spot. It rolled with very little effort as if nothing was wrong. I was relieved since that should rule out a mechanical failure in the gearbox. I tried all gear level settings and it behaved the same.

I have read about folks having issues with the shifter, but mine is working normally. I don't have the car here as I drove a work vehicle home, but I would like help figuring out what to look at tomorrow to see if it is something I can fix or at least diagnose.

I'll be looking at schematics of the gearbox for the remainder of the evening.

It's a 2012 with 167k km

Thanks

Pete

 

[veimi]

After reading your post more carefully, I realized after posting which I have edited that the possibility of seized rear brakes was not a possibility.

 

[kiev]

Are you having some really cold weather in your location?

The gears are always meshed, so if it rolled with little effort while in Neutral, then i think that rules out a mechanical issue with the gearbox.

The motion of the shifter lever moves a sliding electrical contact, actually 2 sets of sliding contacts, in the cheesy plastic position sensors mounted on the upper left side of the gearbox. The electrical signals must agree between the two sensors for proper operation; a DTC will be thrown for this error.

Is the gear indicator on the instrument panel is showing an incorrect reading as you move the lever thru the gates?

One guess is that one or both of those sensors has a worn set of contacts or is making an intermittent contact, that results in messing with the torque command signal from the EV-ECU to the Motor Controller Unit, MCU.

Another guess is that the rotor position sensor (resolver or encoder) located on the end of the motor shaft to provide position and speed feedback to the MCU, has a defect.

i would guess that some trouble code has been stored and if you could read those out it would pinpoint the issue. i use an iCarsoft i909 scantool to read and reset codes, not sure if Canion or Hobdrive apps can do this, someone else may know.

cold weather can mess with sensor signals; sensors are the cheapest, weakest link in the system; fortunately sensors are fairly easy to troubleshoot and repair. Good Luck on finding the culprit.

 

[1pk]

Are you having some really cold weather in your location?

Last week was down to -8c but today its around +10c

Is the gear indicator on the instrument panel is showing an incorrect reading as you move the lever thru the gates?

I'll check this first tomorrow. I didn't notice

i would guess that some trouble code has been stored and if you could read those out it would pinpoint the issue. i use an iCarsoft i909 scantool to read and reset codes, not sure if Canion can do this or one of the other apps.

The RBS light did come on, and one other but only when I put pressed the accelerator hard.

I'm going to get the i909 and see what codes I can find.

I do hope it's an electronic issue, as I think that it should be less expensive, although I assume the rotor position sensor would be inside the housing?

 

[1pk]

So I get to work this morning and my car was back to normal!

I was quite relieved and I checked it five or six times throughout the day and then I drove it home.

I downloaded Hobdrive and it showed no error codes. I am going to post in the Hobdrive thread and see if anyone has succesfully used it to read codes.

I'm definitely worried about recurrence.

Kiev, is there any way for me to inspect the position switch on the gearbox?

 

[DBMandrake]

I drove to work today, parked and plugged in as I always do. When I left at the end of the day the car was slow to move, it seemed like the e-brake was still on but it wasn't. I pressed harder on the accelerator and it lurched repeatedly as it moved forward almost like something in the gearbox was catching and then releasing.

This sounds like one of the rear drum brakes binding. I've had this happen to me in cold/wet weather. So badly in fact that I pulled up to a traffic light to stop, and could not get moving again even with full throttle! Twice in a few days...

When it binds up, only driving backwards will get it to let go again. This is not an uncommon problem on old drum brakes that are in need of some attention. If reversing gets you unstuck it's almost certainly the rear drum brakes to blame.

Other symptoms can be that at slow speeds (under about 15mph) the brake pedal will be overly sensitive and one of the rear wheels will tend to lock with the slightest touch of the brakes.

Both these problems will tend to get much worse in low temperatures (as the drum shrinks, reducing clearance to the shoe linings) and wet conditions. (As the shoe linings will absorb moisture and become more "grabby")

I knew this wasn't good and not wanting to drive anymore I put it in N to see if I could push it back into the parking spot. It rolled with very little effort as if nothing was wrong. I was relieved since that should rule out a mechanical failure in the gearbox. I tried all gear level settings and it behaved the same.

As others have pointed out, the gears are permanently engaged, so "Neutral" doesn't mean anything in a mechanical sense, Neutral just disables power (and regeneration) to the motor but does nothing mechanical.

Did you push it backwards by any chance ? The brakes will only grab going forwards but will turn freely in reverse since the leading and trailing shoes swap roles with direction of rotation.

I have read about folks having issues with the shifter, but mine is working normally. I don't have the car here as I drove a work vehicle home, but I would like help figuring out what to look at tomorrow to see if it is something I can fix or at least diagnose.

I'll be looking at schematics of the gearbox for the remainder of the evening.

Very unlikely to be the gearbox IMHO.

Personally I would pull the rear drums off and give the rear brakes a good going over or have someone do it for you. I disassembled cleaned and adjusted mine and gave the shoes a slight chamfer on each end of the lining material with a file (which helps prevent the leading shoe from digging in, which is what causes the grabbing and locking up) and while I wouldn't say it's perfect now (still slightly grabby in wet weather) I haven't had any more lockups in cold/wet weather.

Not a fan of drum brakes!

 

[1pk]

When it binds up, only driving backwards will get it to let go again. This is not an uncommon problem on old drum brakes that are in need of some attention. If reversing gets you unstuck it's almost certainly the rear drum brakes to blame.

I know this happened a long time ago now, but I want to let you know that you nailed the cause. It rolled fine in reverse, only moving forward caused the issue. Good Call. The issue has never recurred.