edco

Hey Guys,

Well today on the way to work making a left hand turn into the parking lot, I accelerated and had what sounded like wheel spin. I was not on the gas to the point that the tires should spin "Raining today" my speed was maybe 25mph and I quickly realized that the noise was not normal.

I came to a stop, slight rubbing sound from what sounded like the rear of the car. Engine sounds fine with the exception of the rubbing noise “Not metal to metal or grinding, more of a slight scraping noise” from somewhere aft of the motor. Nothing in any gear, no movement or sound change. I had the car towed "Flat Bed" back to my house. When we unloaded the car I noticed that it continued to roll forward in park I would think even if the TT failed the car would not roll in park.

I put a call in to Bill Ball and we're going to take a look at it. We wondered if any of you have any ideas of what to look for? Could this be a problem with the PSD?

Car is a 91, S4 with electronic PSD, 75k miles any thoughts on where to look would be much appreciated.

We found the problem


Thanks,

heinrich

Have you checked or changed fluidat all? That sound came from my Bronco which turned out to have the original fluid in it .... after 200k miles. New fluid cured it 100%. Btw I have a spare 4spd trans if you need it

edco

We checked the fluid level 3 weeks ago over at Bill's, it was fine.

heinrich

fresh or stale

Bill Ball

The fluid may not be fresh, but this is a complete, sudden power delivery failure. I haven't looked at the car since this event. If the tranny does not shift at all, then it could be a failure of the primary pump. Pretty odd. If it rolls in park, then that points aft of the tranny. The park pawl is mechanical, right? So, it should work even if the primary pump fails.

Other thoughts...
- If he had lost an axle, that would be obvious when moving the car.
- Didn't lose tranny fluid - would be similarly obvious.
- PSD failure??? Don't think it fails like this.
- flexplate, TT breakage - possible but also very unlikely.

???

928Quest

If it rolled forward in PARK then the transmission seems like it is not connected to the rear wheels. Broken shafts from diff to wheels?? Does not seem like both would go at the same time. The diff is pretty bullet proof, might be inside the trans.

heinrich

Old, burnt fluid will clog valve bodies and can cause the trans to fail. Just asking based on the sound described.

FlyingDog

My guesses would be pinion shaft or axle. As Bill noted an axle would probably be noticable when moving the car, so I'm going with pinion.

perrys4

Sounds like what my car did when the tranny went except that I had reverse but no other gears. NOt sure what it was that let loose in the tranny but Greg said it was rare.

animal8526

heinrich... I may need that tranny of yours if he doesnt. dont know yet... if so, how much could you part with it for? and the BIG question is, can you get the 4spd auto's into and 81 easily enough if you are replacing the tranny anywho.

morganabowen

My money is on the torque tube Sounds familiar. Bummer

Bill Ball

I know the TT shaft can snap. This car has been babied. We checked the flexplate a few weeks ago right after Matt bought the car. It had never been touched and the shaft moved less than 2mm. Even so, my first thought was TT shaft too. It can happen but usually under a lot more stress.

If the car tranny still locks in park, I'm going to go with primary pump failure, especially if there is no response to shifting the tranny. If the wheels move despite being in park, then the output shaft seems the candidate.

All very bizarre. This car is a gem and would have passed any PPI...until today.

marton

did the car ever have a LH ecu brain problem causing it to go into 4 cylinder or "limp home" mode? That seems to break the TT pretty quickly.

But as was said, if the TT is broken it would not roll in Park.

Marton

daveo90s4

From what you say, and from my similar experience, I'd be inclined to say Central Shaft (i.e the shaft that transmits the power from engine to gearbox, within the Torque Tube. Could be an axle, but you'vbe got PSD so the car would still drive if it was just one axle that had failed. Most improbable that two axles would fail at the same time. Gearboxes are very robust, and more robust than the Central Shafts. Not too hard to check. Basically you need (safely) raise the car. Visually check rear axles for major problems. If nothing obvious, then rotate a rear wheel by hand with the car in gear, and look to see if the rear (visible) rotating mass at the rear of the Central Shaft is rotating too. If so, indicates a problem forward of this point. The next thing to is remove the black rubber bung in the inspection plate beneath and just rear of the flywheel. With a torch have a good look see in there, and get someone to rotate a rear wheel again. Does the back of the central shaft turn but the front not? Does the front of the central shaft rotate but the flex plate not? If its the Central Shaft that's gone, that's really no big deal, and quite simple to replace. I reckon no more expensive than doing a clutch job on a manual!!.

Does your car have 'cats'?. If so you should be aware of Porsche service bulleting entitled "Broken Central Shaft Behicles with A/T" as kindly emailed to me by Dave Roberts of 928 Specialists. If your cylinder head temp sensors have been making your car run of 4 cylinders, the harmonic vibrations and spikes along the Central Shaft can cause the shaft to snap at, and I quote from the official bulletin "an engine speed of approximately 1,000 RPM, i.e just off idle!!

I can email that doc. to you if you want.

Hope this helps, and that its not the Central Shaft (but if it is, no big deal to fix).

Cheers

Dave Overington
Australia

Nicole

Dave: The cars with PSD will not move one bit, if one axle fails. How do I know???

Well, one day I drove back from Sharks in the Park. pulled up at an intersection and decided to switch to the lane right from me. Gave it a hint of gas, heard a clunk, and the engine spun freely. I was able to let the car roll out to a spot away from traffic and stopped there. Tried all gears, no movement. Had the car flatbeded to DEVEK.

Upon inspection, it was found that one axle had fallen off, and the other one was lose. The (other) shop that had previously fixed a tranny leak must not have torqued the CV bolts properly.

Fortunately, it happened at super low speed. I heard later that if this happens at freeway speed, you can kiss good-bye your rear suspension and part of the body in that area...