matt3383

iTrader: (3)

Looking to get some advice on this.

WE had some trouble getting the vibrations to go away on the car when it was 1st installed. But a set of adjustable LCAs and some adjusting of the pinion angle and we got the vibrations to go from 60MPH(starting at ) up to 120MPH. Now im not going 120 MPH very often but at the track or maybe the random street race it will get up there hehe

Problem is the vibration shakes the whole freaking car. Im assuming the the pinion angle must still be off to some extent. The car is lowered so I am wondering if anyone else has installed one of these rear ends and had/solved this problem? I was thinking about looking into some V6 rear spings or some other set to raise the rear up about 1 inch.

The car drives just fine at any speed below 120, no whine or grinding or vibrations. Just once I hit that 120 ish mark it shakes the crap outa me lol.

Any suggestions?

veee8

iTrader: (40)

What did you do about a driveshaft for the rear end swap?

matt3383

iTrader: (3)

i ordered the drive shaft they recommend for the swap. Im drawing a blank on who makes the DS but it has the upgraded yoke for the 9 inch housing connection and is chrome moly.

BIG BAD BLACKSS

iTrader: (4)

Sounds liek you got the strange that he recomends which is a great peice.

How are you checking your pinion angle, and what is it set at now?

matt3383

iTrader: (3)

using a magnetic angle finder, i believe we placed it on the bottom side of the pumpkin in line with the DS.

neg 2 - 3 degrees on what we set it at, which i thought neg 2 was the money spot on these cars hehe

DiabloFormula

iTrader: (58)

Do you have the long or short torque arm?, if you have the long one, check the angle of the trans compared to where it was originally with the stock crossmember, if it's off, no matter how much you have the pinion angle right your driveline angle will always be wrong.

matt3383

iTrader: (3)

im not sure I will have to check the order that was placed, i thought there was only 1 torque arm and it was adjustable lol.

ssvert99

iTrader: (26)

at those kind of speeds your entire driveline angle(s) are important. as the 9 inch pinion center is lower than the stock rearends this becomes an issue at high speeds. in all therory, your engine angle should be the same as the pinion angle at ride height. the - 2 degree angle is a performance thing to aid in launch. the more angle at the pinion, the greater the chances of vibration. the best way to set it up is 1.5 degrees working angle at both the front and rear ujoint, with the rear joint being negative angle(pinion lower than driveshaft). pinion angle... more is not always better.

matt3383

iTrader: (3)

thanks

After talking to a couple people this was going to be my game plan. I was going to adjust it down half a degree and drive it for awhile and see how it did and just do 1/2 degree adjustments till i found a sweet spot. Just good to hear someone on here confirm it hehe

wrd1972

iTrader: (12)

If its shaking, its pinion angle is a mile off. Pinion angle just being a little off even a degree will not make it shake. It has to be severely off.

If its vibrating, the DS is out of balance.

I went down this road and it aout killed me. My DS was out of balance. I sent it to PST and they repaired. All vibes gone period.

matt3383

iTrader: (3)

I thought if it was the driveshaft it would of made the vibration at different speeds. I can be in 6th gear and it will make the vibration or topping out 4th gear with the same issue. What you said is something i pondered on also cause i thought the pinion angle would only make a growling noise in the rear not a strong vibration.

But like I said before I had this same exact problem before however the speed was at 60 mph. Once I was able to adjust the pinion angle better with the adj. LCAs the MPH moved from 60 up to 120. The vibration at 120 seems a little more intense than what it was at 60 though.... which im sure is in part do to the fact im doing double the speed haha.

wrd1972

iTrader: (12)

When mine vibed, it was smooth as silk till 60MPH and then it came on like mad. Under 60 was fine.

matt3383

iTrader: (3)

alright little tweaking on it today. We adjusted the pinon angle from -2 degrees to -1.5.

Before i noticed around 70mph i would get a very slight drone sound ( blamed it on the exhuast ). This time with the adjustment it seemed to be more quiet around this MPH. Then took her up to 80, nada, 90 nada, 95ish the vibrations started and around 100 they were getting close to what it was at before around 120.

So it seems by adjusting the angle less negative by .5 degree it moved the vibration up in MPH ( opposite of what I and others thought lol ). So next attempt will be to put it back and add 1/2 a degree and give her a run.

Does this seem odd to anyone else lol. Is there anything else I should be looking at? I know drive shaft balance has been brought up, would tire balance have anything to do with it? By the observation posted above it leads me to believe that I am on the right path just need to find the sweet spot for my ride height and setup.

wrd1972

iTrader: (12)

See post 10 AGAIN.
The solution IMHO is right there.

matt3383

iTrader: (3)

Would you mind sharing with me what all you tried to get yours fixed before taking the DS in? I'm not ruling out the DS but why would the MPH change with the pinion angle adjustment if the DS was out of balance? Wouldn't the DS cause the vibrations once it hit a certain rotational speed no matter what? Just trying to understand this better. Problem I have with pulling the DS out and sending it somewhere is the car is my DD hehe

wrd1972

iTrader: (12)

It all started when I had a local shop check the balance of the DS. I was grasping at straws when the problem was very bad gear whine at the time. Finally replaced the gears but now there was a terrible vibe at ~60 MPH>.

Dicked around with the pinion angle for hours. Vibes remain.
Replaced the front u-joint. Vibes remeain.
Took it back to shop 1 that balanced it. They did again and the weights were now in different places. Vibes remain.
Replaced the rear u-joint. Vibes remains.
Dicked with the PA some more. Vibes remain.
Double checked R&P setup. Vibes remain.
Replaced all brake rotors. Vibes remain.
Ran car on jackstands without wheels or rotors. Vibes remain.
Installed Rockland NW tailshaft bushing. Vibes just a little less but the bushing failed due to tight clearance. Vibes remain.
Installed OE rear tailshaft bushing. Barely better. Vibes remain.
Took the DS to shop two for balancing. Vibes remain.
Had the tires balanced. Vibes remain.
Sent the Strange DS to PST for balancing. Vibes gone.

faster_n_you98

iTrader: (31)

If what youe said above^ is how you "set" your pinion angle that is your problem. There is a sticky in this section that has a very good write up on how to set it.



The pinion angle is not Just the angle of your rear end. It is the defference between the angle of your drive shaft and the angle of your rear end.

matt3383

iTrader: (3)

faster_n_you98, thanks hehe. Did some reading on pinon angle and I "think" i learned something lol. Seems to be some debating going on about how to correctly setup the rear end angle.

https://ls1tech.com/forums/drag-raci...ion-angle.html

This thread Madman is stating that you only need to adjust the rear end angle. So I am going to have to assume that the negative angle he is suggesting would be based on what your drive shaft angle is as well.

I watched the BMR video and it seemed a little more confusing than helpful ( plus other posts said the same ). However the video and the Sticky for pinon angle seemed to try and state the same concept.

So what does a lowered, 9 inch rear end car guy need to measure to get this damn angle right?

Slowhawk

iTrader: (12)

The few Midwest rears we did I set pinion by zeroing the shaft.Meaning the rears are actually pointing up at the front.The tranny's were around -4 angle so the rears were set at +4.This keeps the shaft in balance front to rear.

We did try the BMR method and the cars vibrated like crap.We tried Madmans way and it got worse.Not the best for street driving. Going by traction my car still dead hooks 1.5 60's.

matt3383

iTrader: (3)

alright so let me see if i understand this.

You stuck the angle finder on the rear of the trans to find that angle. Then you placed it on the bottom of the rear and adjusted the rear to zero out based on the tranny angle?