Another driveline vibration thread (long)
Posted: Sat Aug 13, 2016 5:37 am
I'm starting this thread as mostly an informational post regarding a vibration starting around 60mph and peaking at 65, then tapering a bit the faster it goes. And hopefully a good outcome without throwing a bunch of unnecessary parts at it. Here's my history with the car-
I was working for a transmission shop at the time, about 3-4 years ago, and a customer brought in is 93 legacy turbo wagon that wouldn't move. Turns out the front diff had grenaded itself. The ring and pinion gears were destroyed, and the diff case itself had cracked around the side bearings. I ended up purchasing the car and fixing it to be my daily driver. It sat for a year and a half or so till I ended up having the time to fix it. It had 3 different size tires on it so they got replaced immediately.
I don't really know for sure if the vibration was there all along, but I started to notice it getting outside the range I would call normal a year ago. Now it is so bad the whole car shakes violently above 60 and it buffetts, almost like a back window is rolled down a few inches.
The pads and rotors were shot so they had to replaced anyways. The tires have been balanced 3 times since 2014 with no change. I was able to borrow an electronic vibration analyzer (EVA2) from another shop. Got it all set up with the sensor on the seat rail and it picked up a pretty intense first order driveshaft vibration. (50 Hz, .14 g's at 65mph). On the hoist, I removed the wheels and secured the rotors to the hubs with a full set of extended lug nuts. Run it up and the same vibration is being picked up. I checked the runout on both sections of the shaft while mounted in the car in two separate places for each shaft. The front is .010" and the rear is .028" which seems a bit high but the Astro vans (which are horribly notorious for vibrations) allow up to .040. Naturally Subaru doesn't publish their specs. The next step was checking the frequency closer to the shaft so I could attempt to balance it with the EVA2's strobe function and hose clamps. I placed the sensor on the rear diff carrier but this time the frequency is 22 Hz at 65mph, totally different. I think the gears meshing in the diff was throwing off the readings. I was running out of time for the day so I just took the rear section off to eliminate everything behind the carrier bearing. Same vibration. At this point I had to start putting things back together so I could drive the car home.
Hopefully in the next week or so I'll be able to pick at it some more and get this narrowed down. The whole point of all this is I don't want to waste hundreds of dollars in parts that will not fix the problem (like I've read a ton of other people do). I'll share more info when I get it pinpointed. In the meantime if anyone else has any suggestions by all means speak up!
Jim
I was working for a transmission shop at the time, about 3-4 years ago, and a customer brought in is 93 legacy turbo wagon that wouldn't move. Turns out the front diff had grenaded itself. The ring and pinion gears were destroyed, and the diff case itself had cracked around the side bearings. I ended up purchasing the car and fixing it to be my daily driver. It sat for a year and a half or so till I ended up having the time to fix it. It had 3 different size tires on it so they got replaced immediately.
I don't really know for sure if the vibration was there all along, but I started to notice it getting outside the range I would call normal a year ago. Now it is so bad the whole car shakes violently above 60 and it buffetts, almost like a back window is rolled down a few inches.
The pads and rotors were shot so they had to replaced anyways. The tires have been balanced 3 times since 2014 with no change. I was able to borrow an electronic vibration analyzer (EVA2) from another shop. Got it all set up with the sensor on the seat rail and it picked up a pretty intense first order driveshaft vibration. (50 Hz, .14 g's at 65mph). On the hoist, I removed the wheels and secured the rotors to the hubs with a full set of extended lug nuts. Run it up and the same vibration is being picked up. I checked the runout on both sections of the shaft while mounted in the car in two separate places for each shaft. The front is .010" and the rear is .028" which seems a bit high but the Astro vans (which are horribly notorious for vibrations) allow up to .040. Naturally Subaru doesn't publish their specs. The next step was checking the frequency closer to the shaft so I could attempt to balance it with the EVA2's strobe function and hose clamps. I placed the sensor on the rear diff carrier but this time the frequency is 22 Hz at 65mph, totally different. I think the gears meshing in the diff was throwing off the readings. I was running out of time for the day so I just took the rear section off to eliminate everything behind the carrier bearing. Same vibration. At this point I had to start putting things back together so I could drive the car home.
Hopefully in the next week or so I'll be able to pick at it some more and get this narrowed down. The whole point of all this is I don't want to waste hundreds of dollars in parts that will not fix the problem (like I've read a ton of other people do). I'll share more info when I get it pinpointed. In the meantime if anyone else has any suggestions by all means speak up!
Jim