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Old 05-08-2020, 11:56 PM   #1
yosemitemtb
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Member#: 23437
Join Date: Aug 2002
Chapter/Region: BAIC
Location: Central California
Vehicle:
'02 WRX Wagon
Original owner blue pearl

Thumbs up PST Carbon Fiber Driveshaft - '02 WRX Wagon

First, a little background information about my car. I'm the original owner of a 2002 WRX wagon with just shy of 240,000 miles on the clock. I have autocrossed it since 2003, putting 60 or 70 runs on it per year. It has seen a few track days including one that ended with a spun rod bearing and a new shortblock. I drive it fairly aggressively with most of the miles being on the twisty mountain roads around my home. The car has been very well maintained and I have not hesitated to take it on road trips of a couple of thousand miles at a time, even recently. The suspension has been modded quite a bit, it is on it's third different set of coilovers, presently KW Clubsports that I had rebuilt last summer. My engine is pretty tame with a vf39 and supporting mods. The clutch is a bit aggressive with an ACT Heavy Duty pressure plate and a 6 puck disc, this factors in to why I bought the driveshaft. Last summer I shredded 2nd gear shifting at red line during a high speed autocross/time trial and installed a JDM transmission and rear diff from a twin turbo Legacy. I was experiencing a slight vibration accompanied by some grinding noise during decelleration prior to the trans swap that got to the point after the swap that the noise was becoming alarming. With as many miles on the car as I have, and after replacing most of the drivetrain, the stock two piece driveshaft was becoming suspect. In the end, it was not the problem, the hub springs on the 6 puck clutch disc rattle and vibrate like crazy!

Now, about the driveshaft. The PST shaft weighs in at 14.7 lbs while the stock driveshaft weighs 22.7 lbs by my bathroom scale. -8 lbs of rotating mass! The fit is very tight. I had issues with one of the rubber covered rear parking brake cables touching the shaft, solved by loosening the brackets that hold the cable and retightening them. I also did a little bit of hammer work to the tunnel above the driveshaft just behind where the parking brake cables come through, there was clearance there but not much. I had another slight rub from my Kartboy rear shifter bushing, that was solved by grinding a few millimeters off of the bottom edge of the bushing. I've put about 5000 miles on the car since the install and dealing with the rubs with absolutely no clearance issues since. I did also grind quite a bit of material off of the heavy steel pad inside of the guard that bolts under the rear yoke, but that was anticipated.

When I installed the drive shaft the first time, I had absolutely no vibrations, or I should say, none from the shaft. With nearly every rubber mount and bushing in the car having been replaced by stiffer aftermarket pieces over the years, my car is a NVH machine! After removing and reinstalling the shaft during some work, I picked up a pretty heavy vibration in the 60-70 mph range. I tried the other three positions to clock the driveshaft to the rear diff which made even more vibration and ended up back with where I had it originally. What I discovered, and have not seen reported anywhere, is that where the driveshaft fits into the transmission effects this vibration also. Over the course of several weeks, I rotated the position of the driveshaft on the tailshaft of the transmission by one spline clockwise until the problem disappeared. I took time doing this mostly because it is a pain in the rear getting all four wheels off of the ground, unbolting everything, changing the position, rebolting and test driving. With each move, the vibration lessened until I found the sweet spot after 8 or 9 adjustments. At this time, there are no discernible noises or vibrations I can attribute to the driveshaft.

How does it drive? My butt dyno likes it, the car accelerates slightly quicker. Other reviews say it is similar to a 20-25 horsepower power add which seems about right. I've also read that the cf driveshafts absorb some shock in the drivetrain, this is probably true but it is subtle enough that I haven't really been able to feel it.

All in all, I think it is a worthwhile mod if your driveshaft needs to be replaced anyway, even if it is just for peace of mind.

Was it worth the $1000 price tag? Probably. With as many miles as I have on the car, it is inevitable that a u-joint or the carrier bearing would fail at some point soon. A new oem driveshaft would come in at only a couple of hundred dollars less with reliability but no performance gains. At the power level my car is at, a 25 hp gain with little reduction in reliability for $1k seems reasonable. I also like that should it break, it is less likely to damage other components under the car and less likely to come through the floor and damage me! I'll also add that Rallysport Direct is one of the best companies of any kind that I have ever dealt with.
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Old 05-09-2020, 12:03 AM   #2
yosemitemtb
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Member Sales Rating: (3)
 
Member#: 23437
Join Date: Aug 2002
Chapter/Region: BAIC
Location: Central California
Vehicle:
'02 WRX Wagon
Original owner blue pearl

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Just for fun, here is video of the run I blew up the transmission on. It goes at about 2:23. If you ever have the chance to go to the Lone Pine Time Trials, do it. It is a stunningly beautiful place to race. I would have been there next week for the 50th anniversary of the event if not for this COVID-19 business.

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Old 05-23-2020, 10:20 PM   #3
Mxcrazy
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Nice write up!!!
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Old 05-23-2020, 11:12 PM   #4
2slofouru
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Chapter/Region: South East
Location: SWLA
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My BOV goes
COVFEFE!

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Cool writeup, I have one on my swapped impreza and it seemed to be smoother at highway speeds. The weight reduction is nice and I like that it eliminates the slop between transmission and rear diff.

I was lucky enough to drive in the San Gabriel mountains many years back, when I had a 95L and lived in Lakewood (temporarily). Saw a car hanging off the edge of a cliff and had to stop at someone's home to ask them to call it in, since my phone had no signal.
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Old 05-28-2020, 08:54 PM   #5
Gilbertron7k
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Thanks for the info
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Old 06-08-2020, 01:09 PM   #6
li.wrx
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You think itís worth it if the cars just a daily?
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Old 06-08-2020, 03:30 PM   #7
MortonCharbo
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2002 WRX Wagon
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Quote:
Originally Posted by li.wrx View Post
You think itís worth it if the cars just a daily?
I have the same shaft on my 02 wagon and wrote a review on it too. Not trying to distract from this one.

https://forums.nasioc.com/forums/showthread.php?t=2917956

If you don't mind the price, I say go for it. Mine is primarily daily driven. There is a very minimal amount of modification I had to do to get it to work. If that, and the price, are no issue for you, then go for it. I highly doubt you'll be disappointed.
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Old 06-09-2020, 02:22 AM   #8
yosemitemtb
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Member Sales Rating: (3)
 
Member#: 23437
Join Date: Aug 2002
Chapter/Region: BAIC
Location: Central California
Vehicle:
'02 WRX Wagon
Original owner blue pearl

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Quote:
Originally Posted by li.wrx View Post
You think itís worth it if the cars just a daily?
If you're needing a new driveshaft anyway, it's probably a no-brainer. If you just want a little more from the car and you've got the $$$, it's a worthwhile mod, especially if you've already done some of the more traditional or popular mods already, turboback exhaust, AccessPort, tune, stuff like that.
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