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Questions for PST Carbon Fiber Driveshaft owners.
Questions for PST Carbon Fiber Driveshaft owners.
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Old 10-22-16, 09:07 PM   #1
ulyssis
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Default Questions for PST Carbon Fiber Driveshaft owners.

I just installed my PST Carbon Fiber Driveshaft with some helpful tips from @dublezero. Thanks again dude.

I have a couple of questions based on the install.

1. Is the front spline, of the CF Driveshaft, that goes into the tranny, NOT suppose to go in all the way? Mine seems to be in halfway. Is this normal? Feels like the driveshaft is too "short"



2. The 4 stock bolts that connect the driveshaft to the rear diff: did the flat part of the heads not sit right up against the u-joint like the stock shaft? I had to wedge a large flathead screwdriver in the gap in order to tighten the nuts, to keep the bolt from spinning.



@dublezero confirmed that his install was like mine. If others, with the PST CF driveshaft, can chime in and confirm (or not) that theirs is the same way, that would put my mind at ease.


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Old 10-23-16, 04:32 AM   #2
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

Top pic. There needs top be gap. The splines slide in and out when your rear suspension and/or transmission moves. That does look large, but halfway is probably about right.

Bottom pic. Can the bolts fit in from the other direction? The heads are shorter than the nuts.
Wait, they are not touching anything, right? Then OK.

ADDED 8/29/19: STI rears don't move and the trans only moves a bit. My bad.
The u-joint and sliding does allow for that trans movement though. Also while all DSs slide there, my DSS does not end up looking like that.
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Old 10-23-16, 05:05 AM   #3
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Default Questions for PST Carbon Fiber Driveshaft owners.

Quote:
Originally Posted by mheyman View Post
Top pic. There needs top be gap. The splines slide in and out when your rear suspension and/or transmission moves. That does look large, but halfway is probably about right.



Bottom pic. Can the bolts fit in from the other direction? The heads are shorter than the nuts.

Wait, they are not touching anything, right? Then OK.


Cool.

I figured the shaft needs some telescoping action due to movement differences between the front and rear. I re-checked the stock shaft and I didn't notice the spline not being in 100% of the way because it has a protective cover welded on to the front joint.

The flat part of the bolt heads do not make contact whatsoever with the wall of the u-joint. In other words, the bolt head spins freely if I attempt to tighten the nut on the other side.


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Last edited by ulyssis; 10-23-16 at 06:17 AM.
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Old 10-23-16, 06:10 AM   #4
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

Quote:
Originally Posted by ulyssis View Post
I just installed my PST Carbon Fiber Driveshaft......
So how does the car drive now ? Initial impression please
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Old 10-23-16, 06:16 AM   #5
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

Quote:
Originally Posted by lowbee View Post
So how does the car drive now ? Initial impression please


I've only taken her out on a mild drive to ensure nothing is binding and the bolts remained torqued.

I'm going on a more spirited drive soon and I'll post up my impressions.


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Old 10-24-16, 12:11 PM   #6
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

Quote:
Originally Posted by lowbee View Post
So how does the car drive now ? Initial impression please


My review here:

I inserted a shaft and it feels good.


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Old 10-25-16, 08:47 AM   #7
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

FYI about the OEM bolts - I had the same situation with my DSS CF driveshaft. The u-joint is just a different design and I did the same as you did (wedge a screwdriver to hold the bolt head in place).
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Old 12-12-16, 10:37 PM   #8
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

The spline looks much further "off" than my 2015 STi. It was seated in the rear of the transmission pretty close to full. Are there any markings or indicators on the shaft itself like a model number? Maybe its possible you have the wrong model year? I don't think the shaft has changed since the 04, but I could be wrong.
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Old 12-22-16, 03:00 AM   #9
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

I have a CF driveshaft on my 15 sti from DSS and it has about the same gap. I wouldn't be worried too much.

The drive-ability is much better. I have a QM twin, which is one of the worst clutches for street driving you can buy, and the car would buck and stall in low gear low speed, say a parking lot. The CF driveshaft doesn't do any of that.
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Old 12-22-16, 03:15 AM   #10
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Default Re: Questions for PST Carbon Fiber Driveshaft owners.

Quote:
Originally Posted by pet3r View Post
The spline looks much further "off" than my 2015 STi. It was seated in the rear of the transmission pretty close to full. Are there any markings or indicators on the shaft itself like a model number? Maybe its possible you have the wrong model year? I don't think the shaft has changed since the 04, but I could be wrong.


I've been driving with this shaft for about 5000kms. No issues. I think I'm good. Others have chimed in saying they have the same gap.


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