kc533

iTrader: (1)

That's funny, I've also got driveline vibration @ 120+ mph as well. I've got it down to either the pinion angle or driveshaft, just haven't had any more time to mess w/ it.

matt3383

iTrader: (3)

little more tweaking. The rear end does not have a good spot to take a measurment off of so take that into consideration.

Rear end set to -2, shaft at +2, vibrations come on around 90 mph
Adjusted the rear down to 0, vibrations come on around 110
Adjusted rear back up to about .5 vibrations came on around 100.
Adjusted rear to 1, and left it. I couldnt get the car up to speed at the time of day.

Now something to note. From 70mph to about 75-80 there is a very small vibration and at 80 MPH the vibration goes away ( this is under acceleration and decel ).

Now under accel from the last setup I could get up to about 100 mph with no vibrations. However on decel the vibrations came on at about 90mph or higher.

So to sum up some stuff and take the angles out of the equation. The drive shaft comes into the rear at a downward angle. With the pinon pointed in a upward orientation gave better ( less ) vibration results. When lowering the pinion to try and match the angle of the driveshaft coming in, the vibrations got worse ( more ).

wrd1972

iTrader: (12)

Place the magnetic angle finder on the face of the housing where the gear case goes. There is a ton of flat area there. Gets no better than that. Place the angle finder on the face of the harmonic balancer to get the crank/tranny angle. These two measurements should be nearly the same +/- 1 degree.

If the angles are even close, then there will be no issue as a result of the angles.
Your problem is the DS balance.

If you have the pinion at -2 and the DS a +2, this is wrong. That 4 degree angles on the u-joints. This will needlessly rob power and wear the u-joints out quicker. If you have it setup right, the u-joint angles will be about 2 degrees.

Vibes will occur if the two u-joint angles are different. For example if the rear u-joint angle is 2 degrees and the front one is =5> degrees, you got vibes. If the rear is 2 degrees and the front is 3 degrees, no vibes.

If the two angles are equal, it is impossible for the angles to be causing the problem which leads you right back to the DS balance.

For giggles I set mine up at 0 u-joint angle (testing only) meaning the crank/tranny, the DS and the pinion where dead straight as an arrow and i still had vibes. Again it was the DS.

IIRC. When my car is on the stands, my pinion reads 90 degrees relative to the ground and the balancer reads 90 +/- .5 or so degrees relative to the ground. The DS at the pinion points uphill 2 degrees. The DS at the tranny points downhill ~1.5 degrees. This gives me a -1.5 through -2 degrees pinion angle.

matt3383

iTrader: (3)

yeah im working on finding a place local that does DS balancing. Problem with this rear end is the bottom of the houseing is about 3 inches wide at has weld beads on both sides. So placeing the angle finder on there gives a bad reading

wrd1972

iTrader: (12)

Do not have a local shop do it. I had two shops do mine and still had the problem and was out a hundred bucks. Send it to PST because they have the high dollar high speed balancer that local shops do not have. It was around 40-50 dollars total and back within a week.

matt3383

iTrader: (3)

Can you PM me some contact info for this company, I have no clue who PST is. Problem with me is this car is my current daily so being down a week is going to have to be coordinated hehe

wrd1972

iTrader: (12)

I know you feel like your chasing your tail, I went through it for weeks. Drove me nuggin futs. Once the shaft came back from PST, it was done.

wrd1972

iTrader: (12)

http://www.pstds.com/
They are in Florida.

kc533

iTrader: (1)

Just food for thought....the driveshafts from Strange are already balanced (not to say there wasn't some error on their part). Provided that a misbalanced shaft was the cause of vibration issues, you'd think Strange would stand behind their product and cover any costs incurred to fix something that should not have even left the factory. I mean, I'm just sayin...I didn't pay a couple hundred bucks for something that's faulty. Does Strange not accept their driveshafts back for re-balancing???

matt3383

iTrader: (3)

Im not sure on Strange backing their drive shafts, but I will go down this path if it is what fixes the problem.

Little more info on the vibration issue. My local car club had a cruise and we played around. At one point on the cruise I did get the car up to the 120 mark... vibration from about 100-120 we pretty decent and I actually past the 120 mph mark. After 120 MPH the vibration went away... confused me some haha. Now the only logic I can apply to this is tires. Tires can have vibrations at certain speeds and the vibration can go away at higher speeds. So with this information I more so believe that the drive shaft very well could be the sole issue I am having.

I will report my findings later this week. I am dropping my car off at my local guy and letting him go at it. We found a local DS balancing shop that does lots of race applications. I believe we are also going to look at swapping around some drive shafts that he and others have to change the material of the drive shaft ( aluminum and such ).

matt3383

iTrader: (3)

well update is the drive shaft was fine. The only other idea we have is getting the other torque arm mount from Eric ( i have the dual mount now ). The y-pipe mount has more mounting locations for the torque arm up to about an inch lower than the one i currently have.

matt3383

iTrader: (3)

took the DS somewhere that can balance up to 8k RPM's... and not a flinch. They were able to spin it to 11k with no issues.

Any other ideas?

matt3383

iTrader: (3)

Figured I would revive this old thread to post up what fixed it in case anyone else is having similar issues.

It was the drive shaft. I ordered a new aluminum DS, vibrations are gone. Should of posted this a long time ago haha

LiT1_up

iTrader: (16)

which drive shaft did you buy?

matt3383

iTrader: (3)

I went with PST's street / strip aluminum

STEEPSS

iTrader: (30)

This.

My money is on the working angle of the front u joint being too great. As stated way early ITT by MWC, measure all the angles of your driveline, and go from there.

matt3383

iTrader: (3)

hmm you didnt read my update like 3 posts up did ya? hehe it was the driveshaft.

wrd1972

iTrader: (12)

Click here for the solution to my persistant driveline vibration problem.
https://ls1tech.com/forums/manual-tr...vibration.html