Rear tires not engaging?

[J_C]

This morning I had my new revision from Torrie so I thought I would test it out. First wot was from a dig and the front tires spun like crazy so I let out. Second time was from around 20-25mph with the same results? Could this be my PTU going out or tune related? This morning was the first time I've ever noticed the car not engaging the rear wheels so I'm pretty worried

[SHOdded]

Were you normal-launching or brake boosting?  What tires do you have on now, tread depth, and at what psi?  May need to disconnect the neg terminal on the battery for 30 seconds, let it relearn.

Usually datalogging and dialing in the torque management helps a lot, so I would do that with Torrie.

[sholxgt]

I doubt that it is tune related.  Traction control can hide a bad PTU.  I'm guessing you turned off the TC to test the tune and that exposed the bad PTU.

[J_C]

Were you normal-launching or brake boosting?  What tires do you have on now, tread depth, and at what psi?  May need to disconnect the neg terminal on the battery for 30 seconds, let it relearn.

Usually datalogging and dialing in the torque management helps a lot, so I would do that with Torrie.

This was a brake boost launched from a dig but acted the same going wot from a roll? This is with stock Michelin's which never spun like that before.

[J_C]

I doubt that it is tune related.  Traction control can hide a bad PTU.  I'm guessing you turned off the TC to test the tune and that exposed the bad PTU.

Yes, traction control was off which I always do before launching the car. This just happened to be the first time all power went to the front wheels and spun like crazy

[AJP turbo]

The ptu is spinning all the time and it keeps the driveshaft spinning...the rear end is electronically activated when needed so i doubt its the ptu

[sholxgt]

The ptu is spinning all the time and it keeps the driveshaft spinning...the rear end is electronically activated when needed so i doubt its the ptu

Hmm...I see what you are saying AJP.  Strange thing is there have been several reports of dealers replacing the PTU on cars with non-functioning AWD.  If it is seized, is there something between it and the motor that can slip instead?

My understanding is that, on the cars with a failed PTU, the driveshaft has not been spinning to provide power to the rear.

[glock-coma]

Your right front half shaft is what actually engages the PTU as AJP said. I highly doubt
there's a mechanical issue causing it not to spin, you would definitely know.
Have you talked to Torrie? Any awd off lights on the dash? If your running torque there's a PID for the awd engagement from the clutch pack.


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[Gray Brick]

If I drive aggressively and heat up the drivetrain I get excessive wheel spin  from the front wheels.

When I pull over, turn off the car and let it cool for 5-10 minutes it goes away.

I am leaning towards the RDU getting overheated.

[AnotherGreenFusion]

If I drive aggressively and heat up the drivetrain I get excessive wheel spin  from the front wheels.

When I pull over, turn off the car and let it cool for 5-10 minutes it goes away.

I am leaning towards the RDU getting overheated.

Had the same thing happen to me last night at NED. If I hot lapped, by the time I got to the 3rd or 4th run I was pretty much running FWD only it seemed from all the extra hop I would get.

Need to get some AMSoil into these parts.

[J_C]

Your right front half shaft is what actually engages the PTU as AJP said. I highly doubt
there's a mechanical issue causing it not to spin, you would definitely know.
Have you talked to Torrie? Any awd off lights on the dash? If your running torque there's a PID for the awd engagement from the clutch pack.


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I've spoken to Torrie and he wants me to retrieve the stock files and send to him before anymore flashing. There wasn't any dash lights on at all but this happened 5 minutes before getting to work in the am. I hope this can be resolved without returning to stock before bringing to the dealership

[sholxgt]

Keep us posted and good luck!

[J_C]

Keep us posted and good luck!

Thanks!
Well, I loaded my last tune and the awd system worked fine this morning. It's hard to say if yesterday was a fluke or if it was something in the revision. I'm going to send the current file to Torrie after work to see if he can find anything but it runs great so far!

[Gray Brick]

Do we know what would cause the rear to not engage?

Is there a temp sensor in the RDU giving the awd notification it is hot?
What about in the PTU?
Or something else?

[AnotherGreenFusion]

I recall reading somewhere that is has its own temp controlled cutoff. Not sure how it works though.