01 GP GT 3.8 Speedometer, shifting issue.

[thebruce]

New to me car, getting all the wrinkles ironed out before I let the kid drive it.

The speedometer in the car works properly when turning to the right. Even a very small pressure on the wheel to the right will make it work. Like if I was driving on the left side of a crowned road it would be enough. The transmission also shifts very firmly to roughly when the signal drops off. The speedo never reads 0, but only indicates a fraction of the actual speed. Very rarely can I complete a straight section of road or a left turn and the speedometer reads correctly.

The right front hub is sloppy, and will be replaced at my earliest convenience. The wheel speed sensor is part of this assembly or will be replaced at the same time if not.

I have read that the WSS is not tied to the VSS signal/speedometer readout in any way, but want to be sure of this before I go tearing into the dash/cluster/steering column to look for rubbed through wires or other fun stuff. Wondering exactly how and where the vss ties into the signal for the Trans. to shift and if it is a separate issue from the speedo, or if it gets a signal after the speedo.

I have replaced the VSS with new Delco unit, no change in behaviour, no excess metal shavings came out with it. Transmission fluid is nice and red, no burning. I have inspected the wiring harness from the VSS connector, all the way to the PCM in the airbox and found no damaged areas.

I have also installed new loaded struts on the rear, upper manifold (and pcv valve), aluminum lower gaskets and coolant elbow... probably other stuff completely unrelated to this issue with no change in behaviour.

Any guidance is appreciated, thanks in advance.
Steve.

 

[QUICKSILVER462]

I have heard of cases where the reluctor ring on the differential (final drive) comes loose or shifts on the diff. A simple check is you could remove the VSS sensor from the diff. cover and look inside
the hole and get a visual to make sure the reluctor ring is still in place, and even put a screwdriver on it and make sure it is still secure on the differential (final drive) unit.

If you have access to the equipment your could even put a scope on the VSS singal and compare to a known good patter to verify the signal.

 

[thebruce]

Thanks for the reply, QUICKSILVER462, you nailed it.

Over the winter I shy away from doing unnecessary work on vehicles, so the car didn't get much attention. The problem fixed itself for a while and then shat the bed again. Leave it in 3 and it was acceptable.

I intercepted the signal from the vss at the pcm yesterday with a voltmeter and observed a voltage fluctuation proportional to the fluctuation in the speedometer output, so that sort of led me away from the pcm.

This morning I got adventurous and lifted the front end, took off the passenger side tire and removed the vss. I stuck my finger in there and at first the tone ring seemed solid, but with a little effort I got it to slide around.

I bent a flat blade screwdriver at about 90* using a torch, and slowly worked the ring inboard back into position while rotating the hub in neutral. Reinstalled everything and took it for a flawless test drive.

This "fix" may or may not last. From what I see it looks like I can take a piece off the end of the transaxle to get at the ring. I'll have to remove the CV axle, and will have to replace an oil seal and a gasket. A bit of locktite bearing retainer on the ring and it should be permanent. Easy easy.

It'll probably leak out a bunch of tranny fluid when I do this so I'll grab a filter and a shift kit and do that at the same time. Sounds like a fun afternoon.

The last little thing that she does wrong is start hard when warm. It seems like vapour lock or low fuel pressure. If I hold the throttle down it starts faster, but will stall if I let off too soon.

For the moment that's small potatoes, and I'll start tracking that down after the litany of other mechanical adventures I have waiting for me this year.

Cheers.