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Old 04-14-2022, 12:31 PM   #1
dirtcrazy
Scooby Newbie
 
Member#: 220831
Join Date: Aug 2009
Chapter/Region: SWIC
Location: SE Arizona
Vehicle:
2000 Impreza RS Sdn
Drk Blue

Question Driveline slipping/grinding

I am chasing a driveline slip/grinding sound at moderate or higher acceleration.


About my Subie:

It's in my 1999 Legacy Outback with an EJ205 swap with a VF48 and 15lbs of boost running through the original N/A 5-Speed. It's making.... a lot more power than the original EJ25D. The car's been turbocharged for about 4 years, now. I daily drive it, RallyX it, and AutoX it.

Chassis has 140K miles on it. Center diff was swapped out with a known good one a week after I got the car since it was binding after a moderately long drive on the interstate. It has been fine since then.





Little background:

I replaced the struts and had it aligned. The following day I took it to work. I got about 5 miles from home, stopped at a light, and when I went to accelerate, the car began acting like the clutch was completely gone. Weird, since it's got less than 1000 miles on it. And, it's a stage 3 clutch.
No pops, no bangs. It just quit accelerating normally. The car could still move. Just.... slowly. So, I limped it back home again doing no more than 20mph.

While driving home, I noticed that the RPM and speedometer were still in sync. So, I came to the conclusion something in the driveline must have let go. Sure enough, the driver's rear axle had popped out of the rear diff. I reinstalled the axle and now I have this driveline slip that won't let me accelerate at anything but at a slow-poke pace!



What I have done so far to diagnose the issue:

I pulled the rear diff out and inspected it. The fluid was clean, the gears looked a little worn, but not broken. No excessive play or weird feelings when spinning the diff.

The axle boots are fine. They are not twisted (like if the CV joint was slipping) and the splines on the diff end look normal, no splines missing, abnormal signs of wear, or anything. They pop in and out of the diff normally. (Needs a decent mount of force to pop them out of the diff. So, the the cir-clip is doing it's job) The outer ends are still stuck in the hubs. Probably rusted in place. The car did spend a year on the east cost before moving to Arizona...



My next plan is to press the axles out of the hubs and inspect them. The slipping, grinding, and banging is coming from the rear. So, that's where I am searching.


Am I chasing the correct rabbit? I don't *think* it's the front. It doesn't feel like it is. I also don't think it's the center differential, but I'm willing to chase that rabbit if I'm wrong in my thinking. It'll do it in 1st, 2nd, and 3rd gear so I don't think it's a transmission issue.



I'm super puzzled with this one. The car didn't like, shake or make loud noises or anything. When that axle fell out, it did it quietly. And now, I've got this terrible slipping/grinding that I can't seem to track down!


I wanna go RallyX'n Saturday, but the car is being difficult!!!
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Old 04-14-2022, 01:26 PM   #2
yarrgh
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Member#: 80465
Join Date: Jan 2005
Chapter/Region: RMIC
Location: Denver
Vehicle:
2001 2.5RS
Black Diamond Pearl

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get it up on jackstands, put it in gear and observe.
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Old 04-14-2022, 01:41 PM   #3
dirtcrazy
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Member#: 220831
Join Date: Aug 2009
Chapter/Region: SWIC
Location: SE Arizona
Vehicle:
2000 Impreza RS Sdn
Drk Blue

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I did and there was nothing out of the ordinary found.
I could slow a tire down to a stop and it would spin the other side faster. like it should. Let go, and it would kinda try to catch up, but no funky sounds, vibrations, or anything.
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Old 04-18-2022, 03:27 PM   #4
dirtcrazy
Scooby Newbie
 
Member#: 220831
Join Date: Aug 2009
Chapter/Region: SWIC
Location: SE Arizona
Vehicle:
2000 Impreza RS Sdn
Drk Blue

Default

Turns out, it was a failed CV joint. It looked fine. No funky cracks, leaking grease, or anything! But, as I was pulling things apart again, I discovered the inner joint could extend far further than it should! In fact, it locked up on me as I was removing it out of the diff.

So, two new axles later, (decided to do both sides since I do race the car) the slipping/grinding has been remediated!
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