Wicked vibration, cant seem to kill it

[ThoR294]

I set the pinion angle at the rear to -1. but I didn't account for the trans. I think thats the culprit. Hopefully this friday I will get a chance to take it to my uncle's garage in Lebanon and set it on the alignment rack to check everything

[smoke_em94]

Let is know how u make out

[The_Bishop]

Did you set the pinion angle *in relation to the engine angle*?

When they say -1*, they don't mean -1* in relation to the ground. It's -1* in relation to the engine angle.

Say, if your engine is tilted back 4*, and you set your pinion angle at the same 4* back, you are at 0. If you set your pinion at 3* back, you are at -1*.

[ThoR294]

Originally Posted by The_Bishop

Did you set the pinion angle *in relation to the engine angle*?

When they say -1*, they don't mean -1* in relation to the ground. It's -1* in relation to the engine angle.

Say, if your engine is tilted back 4*, and you set your pinion angle at the same 4* back, you are at 0. If you set your pinion at 3* back, you are at -1*.

That is exactly what I DIDNT do in the first place. I just set the rear to -1* and I thought I was golden. Like an idiot, I didn't do digging. 3-4 years later, I now know what to do. Hopefully Friday I will be able to measure the engine angle and the rear, and do exactly like you said.

I'm so mad at myself right now. I am pretty convinced it is the driveline angle. Especially after reading through LS1 tech horror stories with vibrations and driveline angles fixing vibration issues.

Im so anxious for friday. I WANT THIS FIXED.

[Dudbird113]

I just used a pinion angle measurer thing (can be found in tool section of homedepot) and put it on my driveshaft. Only use that because u want alittle deflection in the drive shaft for the u joints.

[The_Bishop]

Thor, the reason I know about it is I was chasing down a drive line vibration, too.

[ThoR294]

Measured it as best as I could. Trans was pointing down 3* and rear was down 1*. so I shimmed the trans mount so it was pointing down 1* and rear pointing up 1* (as what my UMI angle finder said...)

It's still there, but its not as bad. I wonder if the angle finder just sucks and it's not getting an accurate reading... or my driveshaft may be too short since the car is lowered?

[3.4 grape of wrath]

I feel your frustration and anger. I had a vibration problem a couple years back and kept a diary of things that I checked and replaced. Similar to what you are going through. It ended up being the exhaust system. The combination of the rubber hangers hardening and the alignment was off from lowering the car. The noise would change when I shifted from drive to reverse. The way I discovered it was tapping the pipes with a rubber mallet from front to back with the suspension loaded and heard this loud vibration towards the rear.
I replaced all the rubber hangars and realigned everything and the vibration was gone.

[The_Bishop]

Wait, if you have an adjustable torque arm, you adjust *that* and forego the shims on the stock trans mount.

[ThoR294]

Originally Posted by The_Bishop

Wait, if you have an adjustable torque arm, you adjust *that* and forego the shims on the stock trans mount.

From what I read, everyone's transmission was pointing up... and mine was pointing down. So I didn't know if its because of the UMI relocation crossmember was making it point down. I can always remove the shims and go again.

I just fine tuned it by just winging the Torque Arm adjustment. It is not noticeable at ALL in gear/under throttle. but if you push the clutch in you can feel it. No where near as bad as before, though.

[WildBillyT]

http://www.stevesnovasite.com/forums...d.php?t=211270

Read up. The two guys in here are very tuned in to this type of thing. One's a senior guy at Chris Alston's.

[ThoR294]

I have the relocation crossmember for the Torque Arm... I wonder if the bushing placement for the T/A has anything to do with a vibration

[The_Bishop]

The transmission *should* point down. The engine/trans angles towards the rear.

[ThoR294]

I guess now that I think about it, that does make sense... The rear is lower so it should be down. duhh.

[sweetbmxrider]

The rear will rotate under acceleration thus aligning the driveline angles to 0* or so I have read on le internets.

[WildBillyT]

Originally Posted by sweetbmxrider

The rear will rotate under acceleration thus aligning the driveline angles to 0* or so I have read on le internets.

This is why traction bars exist

[The_Bishop]

Rotation is *much* lower on our torque arm cars. At stock(ish) power levels and with an aftermarket arm, I'd be surprised if it was more than .5*, and I'd be willing to bet it's closer to 0*.

[greenformula92]

I had a vibration too. turned out to be a combo of bad bushings in both the stock LCA's and the stock Panhard rod. just saying what my issue was. yours could be totally unrelated

[ThoR294]

I think it had it when i swapped the panhard out as well. I am going to put in poly/rod LCAs at some point. I was silly and bought them a long time ago

[ThoR294]

Finally figured it out. I bought this angle finder:

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

I re-installed my poly transmission mount. Transmission was pointing down 3 degrees. I set the rear to point UP 2.65-2.75 degrees. Vibration is now GONE. I have a slight vibration at 90mph.... but that is probably from everything being solid, and it is NO WHERE NEAR as bad as it used to be. THANK GOD I can't believe it took me this long to do this research and figure out how to properly set the angle. I was just setting the rear before *sigh*

[sweetbmxrider]

This is how you learn.

[ThoR294]

Originally Posted by sweetbmxrider

This is how you learn.

Indeed. Lesson learnt :P

[ThoR294]

so Im bringing this back up. It is still there, and I have moved the angle everywhere I am pretty sure. Still stumped on how to squash this. I am wondering if its the relocation X member that is giving me the wicked vibe

[B4C]

I didn't read the whole thread but I see you have an adjustable phb listed in your sig. Have you ever had it on an alignment rack to check if your rear axle is centered?

[ThoR294]

I did the whole pendulum thing to center the rear when I first installed that bar.

On LS1TECH, I was told to try and measure the transmission angle from the shifter plate. i may be getting a bad reading from the transmission under the output shaft. Also, was told to have -2 total angle... so if the trans is -3 the rear should be -1 and that should work for me. so I am going to try to pull the console out on my uncles alignment rack and do it AGAIN... and pray to the vibration gods