Horrible vibration at 100km+

[Big T]

Hey all.

I have an odd one for you. Car is fine up to around 90km or so. The vibrations can be felt at lower speeds but it gets very bad above 90km. Over this speed, putting the car into neutral/clutch in creates a horrible vibration. Something like going over those rumble strips on the side if the road but far worse. With the clutch engaged, even if there is no throttle, there is very little vibration. So the diff needs load to stop the vibration.

Car is an ae86 4agte with w57 and f series with tru trak torsen, single piece tailshaft. The vibrations became more noticeable after putting in the twin plate clutch but it was only on accel and decel whereas now it is in neutral.

I did originally have rose jointed 4 link but they were destroying shock bushes and mount points so just switched back over to oem links. The adjustable arms were set to factory length.

My guess is that it is pinion angle related and going back to rubber arms has allowed greater misalignment of the angle. Would like to see what other people think.

Fire away your thoughts.

Eddie.

[Celica RA45]

go to a 2 peice as the f series diff is off set .1 other thing is it a new clutch and presure plate or 2nd hand.
maybe it with flywheel needs a balance .and last check your wheels to see if any wheel weights have come off or any mud has stuck to the inside of your rims
another way of checking is put the car up on stands and going through the gears see what the back is doing , then take tail shaft out and do it agian to see if you still have the vibration
just make sure you have either a spare front shaft you can put in the back of the gear box so you dont loose any oil

[lexsmaz]

I assume when you throw the clutch at 90 kmh you are letting the revs fall away too to idle ?? .. And if so I would be looking at the drive line as you mentioned & I would imagine you have a Very bad Uni there ..

[allencr]

No vib when revving in neutral, clutch engaged or dis-engaged, then it's not the clutch and/or flywheel.
Pinion angle means nothing except that it's a convenient place to measure from and that it changes because the rearend rotates opposite the wheels when under a load.
The U-joints must both have the same angle, vertical & horizontal, and be less then about 4degrees and not zero.
Check any 4WD site for lots'o stuff on U-joints/driveshaft setups.
http://www.driveshaftshop.com
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Or just bad/worn U-joint/s whose old wear spots don't like the slight change to the different links.

[oldcorollas]

and check driveshaft bolts are tight..
and pinions backlash...
and that pinion angle and gearbox axis line up (as above)

[Big T]

Thanks for the suggestions fellas. This was the issue...



The yoke itself was twisted at the unis and had twist in the spline section as well. There were also no bearings left in either front or rear uni, just metal powder.

Methinks I need larger unis to deal with the power output so am on the hunt for a g-series pinion flange that will fit an f-series mx13 diff. If anyone has a spare mx83 2 piece tailshaft lying around, i'm looking to purchase one. Or a yr22 centre with the larger flange.

Cheers.

Eddie.

[oldcorollas]

good effort there!