Vibration with FRPP 1-piece Driveshaft

[s9669s]

2011 Mustang GT, lowered on H&R race springs with Ford Racing adjustable Panhard...

Recently installed an FRPP 1-piece driveshaft along with Whiteline adjustable LCA's, and J&M LCA relocation brackets. After noticing a new/different vibration, I put in on an alignment rack to adjust the pinion angle per the BMR video specs (3 degrees lower at the rear end vs. the trans angle with factory UCA), but the vibration did not seem to change.

The vibration I am getting, I feel through the floor/console/seat under moderate to heavy acceleration load from ~3k rpm, and getting more and more noticable and more coarse at higher RPM. If I push in the clutch after a run to redline and just coast, the vibration does not immediately go away--it seems subside over the course of a couple seconds as rpms drop. Just coasting along or cruising in gear at the same speeds, I get no noticable vibration.

My initial thought was pinion angle, which is why I adjusted it, but that seems to have made minimal / no difference. Is this normal? Could it be engine harmonics I am feeling now that the heavy stock driveshaft is out of the mix? Is there something else I should try?

(I also have a Whiteline adjustable UCA that I could put on, but have not yet.)

 

[blacksheep-1]

A couple of things, I have never adjusted the pinion angle or used relocation brackets in ANYTHING, not even the world beating S197s that were run in Grand Am and PWC.in fact all that was run was a Gt500 stock upper and FP lower trailing arms.
It was that simple.
Secondly, turn the drive shaft 180 degrees and see if that helps the vibration. Look it over for any dents that may have come from shipping it.

 

[xr7]

For normal usage the driveline u-joint angles need to offset each other. If the transmission/engine is at a 2 degree drop (front to back as viewed from the side) Your diff needs to have the relative tilt, front up with a 2 degree drop. If your angles are off you get vibrations from torsional stress, the faster you spin it the worse it gets.
The u-joint should also run some angle, 1/2 to 1 degree minimum.
If your racing, especially drag racing that's a whole different story.
There are YouTube video's and I think Tremec has some stuff on there web site.
What's happening is the driveshaft after the first u-joint is speeding up and slowing down 4 times in one revolution. With the second u-joint set at the same angle it takes that cycling input and returns a constant speed output.

 

[s9669s]

Thank you both for the responses...what has me scratching my head here is that the vibration seems to occur only under load, and does not go away immediately when I push in the clutch (at high rpm)...

@blacksheep-1 - I know my setup varies from what you run/ran. Some of it may be due to the different discipline (autocross), but I also have not tried it on course yet. Regarding the driveshaft, I saw no visible damage--will likely try clocking it as one of the next step.

@xr7 - my understanding (based on what I have read) was to shoot for pinion angle parallel to crank angle under load, and hence you would typically have the pinion angle at 1-3 degrees lower than the trans tailshaft angle (depending on the UCA bushing type) such that under acceleration, the front of the diff rises up into alignment with the crank orientation.

When I measured my car on the rack today, the pinion was just over 4 degrees down versus the crankshaft angle, so I brought it up to about 3 degrees down based on the BMR S197 video alot of folks on Mustang forums seem to reference...thoughts welcome on the angle

 

[tgt2017]

Thank you both for the responses...what has me scratching my head here is that the vibration seems to occur only under load, and does not go away immediately when I push in the clutch (at high rpm)...

@blacksheep-1 - I know my setup varies from what you run/ran. Some of it may be due to the different discipline (autocross), but I also have not tried it on course yet. Regarding the driveshaft, I saw no visible damage--will likely try clocking it as one of the next step.

@xr7 - my understanding (based on what I have read) was to shoot for pinion angle parallel to crank angle under load, and hence you would typically have the pinion angle at 1-3 degrees lower than the trans tailshaft angle (depending on the UCA bushing type) such that under acceleration, the front of the diff rises up into alignment with the crank orientation.

When I measured my car on the rack today, the pinion was just over 4 degrees down versus the crankshaft angle, so I brought it up to about 3 degrees down based on the BMR S197 video alot of folks on Mustang forums seem to reference...thoughts welcome on the angle

Hey just wondering if you found a fix for this vibration issue? I have the exact same issue on my 2014 GT with an FRPP driveshaft. I've since added an adjustable UCA and attempted to set my pinion angle per the same BMR S197 video you reference and I still have the vibration. Pretty annoying.

 

[s9669s]

I progressively brought it down to about 1.5 degrees (from the 3 degrees in the BMR video), which removed the vast majority of it. I still have a little bit of vibration at high RPM (over ~5,500).

When I moved to 2 degrees, everything was gone except for that high RPM vibration. I went on to 1.5 degrees after calling the FRPP tech line, but it did not make much if any difference.

I'd be interested to hear if you still have a high RPM vibration after adjusting...I am thinking that may be normal / engine-induced because I feel a similar / same vibration if I rev the engine in neutral.

 

[ArizonaBOSS]

I am thinking that may be normal / engine-induced because I feel a similar / same vibration if I rev the engine in neutral.

You may want to look at your motor mounts; make sure they have not loosened at the connections to the K-member, mount-to-bracket nuts, and/or bracket-to-engine bolts. Also if they are the OEM mounts (liquid-filled, IIRC), make sure they are still intact to begin with.

 

[LuxurySportCoupe]

Off chance, but since the vibration seems to get better as engine rpm drops with the clutch pushed in: check to make sure the exhaust clamps at the front of your midpipe are oriented so the bolt isn't contacting the floor pan.
I installed a FRPP one piece driveshaft and bolt-in x-pipe at the same time. I didn't pay attention when I tightened the exhaust clamps back up, took it for a test drive and the NVH was HORRIBLE. Got it back up and stands, looked around, saw the exhaust clamp bolt contacting the floor pan. I fixed that and haven't had any vibration issues since.