QA1 GT350 CF Driveshaft

[Epiphany]

One issue I had during the install is that there was such a small amount of clearance on the differential side to tighten the hex bolts on the driveshaft (not the adapter). I had to try 3 different 10mm hex tips to find one that will fit there....
Also for those of you who did this on jackstands, how the hell did you manage to put 85 ft lbs on transmission hex bolts laying down there? You need a big 1/2” torque wrench for this and need leverage to do it.

That's the way typical RWD driveshafts are. Every Mustang chassis I have owned throughout the years (dating back to a '67 Dan Gurney Special Mercury Cougar) posed some challenges when installing a driveshaft. You do what you have to do to get it done.

Just yesterday I installed an interesting driveshaft in a '90 coupe with full Maximum Motorsports suspension, etc. Even though the shaft was smaller in diameter than the FRPP shaft I was replacing, I had to employ some "alternative" torque sequencing techniques. It's just the way it is. That said, I found the CF shaft install on the GT350 to be the easiest I've ever done. Fitment was perfect.

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[2JZFAN]

I'm just over here waiting on a deal. If anything worthwhile drops, make sure to share with your forum family!

 

[Burkey]

No idea how I missed all this but THANK YOU @Epiphany for your time and diligence in the thread. Much appreciated.

 

[Epiphany]

Thanks Burkey. I had hopes that QA1 would eventually offer a CF GT350 driveshaft and when they did I jumped on it. I'm fairly thorough when inspecting a given part and found the effort put forth on this one to be top notch. Thankfully, I won't have to do it on my upcoming GT500.

 

[Burkey]

All this talk of driveline angles has me curious...
@Epiphany and @BMR Tech can you offer some insight here?
I lowered my engine 1/4” about 18 months ago.
I didn’t bother to calc the driveline angles because I figured it would be “near enough” (insert facepalm here)
Meanwhile, my stock driveshaft has taken a massive shit. Centre bearing support is “rooted” (Aussie tech term)
High rpm, blower assisted clutch dumps at the strip wouldn’t have helped any.
I have a QA1 on order, just waiting for it to arrive.
My question is, should I actually spend the time to get it perfect or as near to perfect as possible OR, would I do nearly as well to just shim the gearbox down 1/4” and call it a day?
My base understanding is that you want some angle between the uni and the shaft, more than 1* but as little as possible. Is this correct?

 

[mmakam2]

How are people's vibrations over 120mph with the QA1 carbon shaft?

I had both the DSS carbon and the QA1 SFI approved carbon on my 15 GT, the DSS vibrated so bad felt the car would fall apart over 100. The QA1 was much better but still a fairly significant increase in vibration over the factory 2 piece.

Ideally, regardless of noise or resonance, if the shaft is properly balanced, you shouldn't get any vibration regardless of the speed, but that hasn't been my experience at all with the aftermarket shafts.

 

[Epiphany]

My question is, should I actually spend the time to get it perfect or as near to perfect as possible OR, would I do nearly as well to just shim the gearbox down 1/4” and call it a day?

If you want optimum performance from the mod I'd recommend verifying driveline angles and addressing them appropriately. Production variances indeed exist and given that you lowered the engine I'd be even more inclined to take a closer look.

...if the shaft is properly balanced, you shouldn't get any vibration regardless of the speed...

That isn't always true. What are your driveline angles?

 

[mmakam2]

If you want optimum performance from the mod I'd recommend verifying driveline angles and addressing them appropriately. Production variances indeed exist and given that you lowered the engine I'd be even more inclined to take a closer look.


That isn't always true. What are your driveline angles?

On the vehicle which had the vibration issue, the motor, trans, and diff were all in the stock mounting positions.

 

[Epiphany]

That's what I was touching on in my response to Burkey. "Stock mounting position" doesn't mean optimum nor that every car is identical. There are ranges that are acceptable, typically. If you are going to the trouble of swapping a driveshaft I'd recommend you spend a few more minutes verifying relevant angles and tweaking them if possible and necessary.

 

[mmakam2]

That's what I was touching on in my response to Burkey. "Stock mounting position" doesn't mean optimum nor that every car is identical. There are ranges that are acceptable, typically. If you are going to the trouble of swapping a driveshaft I'd recommend you spend a few more minutes verifying relevant angles and tweaking them if possible and necessary.

I see what your saying, without the carrier bearing the shaft is going straight from trans to diff.

I guess is the goal to match what it was from the factory or is there some best practices for getting driveline angles right? "A little off zero angle" is not very specific i guess.

 

[Epiphany]

I touch on this earlier in the thread. The factory driveline angles are for a two-piece driveshaft. You can indeed optimize them for a one-piece. Thankfully, CV joints are fairly forgiving but that doesn't negate the fact that their may be room for improvement.

 

[mmakam2]

CV joints are designed to run through a wider range of angles, IE halfshafts in a IRS car.

I don't think the vibration issues people are having are due to this. I think the one piece shafts are just SUPER sensitive to any imbalance. Even if the balance issue isn't in the shaft itself, the onepiece is going to transmit the vibrations through the chassis.

Its going to be a gamble basically if you pick up a QA1 or DSS if your car will run like glass up to 150-160. Personally I am going to put driveshaft loops on my stock shafts, wait till I break it, then go down the rabbit hole with the 1 piece option. My experience with the carbon shafts and my GT have turned me off completely.

 

[honeybadger]

Quick note: when I installed my qa1 and did my first shakedown, I didn't notice any Nvh. Top speed was only about 125-130, tho.

Between the shakedown and my first day at COTA, I had to drop the trans to replace a rear main seal. When I did my track day, I had some vibrations north of about 120.

After seeing this recent convo about angles, I went and checked mine and found that my trans had slid towards the driver side a bit in the rear. I loosened the mounts and pulled it back. Presto - no more vibrations.

If you're having any added NVH, it's probably something similar.

 

[galaxy]

I was nervous about that just dropping the tranny down slightly for a shifter install. Have alawsys been paranoid about getting it perfectly back in the same spot so I mark the crap out of it, LOL.

 

[Burkey]

@Epiphany
I had a bit of a play with my driveline angles prior to installing my QA1 shaft.
Ended up with this, which seems to tick all the boxes, in terms of “more than 0.5*, less than 3*”
Angle 1 is the U joint, angle 2 is the CV.
Thoughts?

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