ThoR294

iTrader: (6)

Swapped rears, practically same vibration
2 sets of wheels (one set was straightened and road forced with no issues)
its not flywheel/clutch related due to engine off in neutral and the vibration is still there...

I am thinking driveline angle

ChevyOwner

Before I wrecked my 97 z/28 6spd, for a while it did something similar at high speeds(i think 90-100+), and i don't remember exactly what i did to fix it. The most probable thing i can think of right now is (don't remember why) re-install the drive shaft with it being lined up differently.

ThoR294

iTrader: (6)

Like I said, I've put my D/S in multiple times... Same shake every time. Even after it was balanced.

I think it's the angle. I just haven't had time to diagnose it

Also, my rebuilt rear is for sale if anyone needs a 3 channel 3.73 rebuilt rear

ThoR294

iTrader: (6)

Transmission is pointing down 1 degree.... So I set the rear to point up 1 degree. It got better but it's still present. So I put the rear up more, it got worse... So I cranked it lower and it's still there but not as violent

ThoR294

iTrader: (6)

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

1961ba427

iTrader: (26)

Very interesting. I never knew our cars were that sensitive to pinion angle. I mean I know it's important, but didn't know that just the difference of a 2* range would cause such a vibration. I always thought of it as more of a traction tuning tool. On older cars I've ran anywhere from 0* to -4* without problems.

ThoR294

iTrader: (6)

I thought I measured it to the T... I am wondering if the T/A relocation crossmember has anything to do with it. I put the bushing on the 2nd set of holes from the top. IDK how to even tell which hole set to put it in...

1961ba427

iTrader: (26)

If I remember correctly, I put mine in the top position on the TQ arm relocation crossmember. It's a full length UMI adjustable TQ arm, LT1/M6. Moving the front of it up shortens the instant center which should hit the tires harder. I pretty much had to move it up there so it would clear my Y-pipe. As far as the current pinion angle.....all I've done so far is eye-balled it to comfirm it is slightly negative. LOL Sad huh?

unioncarpenter84

iTrader: (22)

welll went to the track there were two other lt1s and i asked if there cars vibrated and they dont get it at all till 110 they said bout their drive shaft having some kinda damper on it near the tranny??

like a rubber bushing?

do u guys

BoostedDSM

iTrader: (6)

Neither of my Driveshafts have that on them, but I had my car out last night finally and I have the vibration at about 110 also.

I'll have to check my angles and see what they are, but my car is all stock susp. wise. Plus a stock balanced driveshaft with almost 192k on it.

ThoR294

iTrader: (6)

the v6 fireturds had a 2 piece driveshaft. (dampener in the middle). we have nothing on the trans...

1961ba427

iTrader: (26)

I think they are talking about the dampner that is on the yoke of most 4th gen driveshafts. The stock steel and 2 diff styles of stock aluminum ones I own have them on there.

AZ2ENVY

iTrader: (2)

When you installed the Poly trans mount, did you install the spacer plate that came with it?
If you did remove that plate, that will create some nasty vibrations.

ThoR294

iTrader: (6)

I swapped the rubber one in, and i did use that plate yes. I used the plate on the OE rubber mount and another steel plate. lol just to push the trans up

AZ2ENVY

iTrader: (2)

Remove those plates, your pinion angle is off with them installed. That alone
will cause vibrations.

ThoR294

iTrader: (6)

They weren't in when the vibration was present. I measured the trans output shaft angle it was pointing DOWN about 3 degrees. I put the plates in and it pushed it up to about 1 degree down still. so I set the rear to 1 up and it got better. I then cranked the rear down a little (which makes no sense) and the car doesnt vibrate at all in gear. You can feel it in neutral but its no where near as horrible

AZ2ENVY

iTrader: (2)

So does it vibrate in neutral with the vehicle in motion? If so does the vibration
Pitch change if throttle is applied?

ThoR294

iTrader: (6)

Correct vehicle in motion over 70mph. Vibration doesn't change in neutral if the engine is revved or shut off. The vibration changes when I push the clutch in or shift to neutral (meaning, a driveline vibration)

Quazz

iTrader: (1)

Tailshaft?

ThoR294

iTrader: (6)

2 different transmissions same vibration. Like I said, it changed when I changed the pinion angle