Vibration from the back end

[VH 1UZ-FE]

I have my 1UZ-FE in my car and was just about ready to go in for the roadworthy then i ran into this!

I changed the rear upper trailing arms on my car (VH Commodore) along with a couple of other bushes and the brakes, then when i put the car down and took it for a drive there was a huge vibration coming through to the cab. It is at its worse when i take off, then it gets softer as i get faster. Here is what i have done about it so far:

1.) took off the tail shaft and the centre rubber mount was split, so i got that fixed and the vibration was still there, but not as bad (which makes me think that the vibration caused the rubber mount to split in the first place).

2.) my old rear upper trailing arms were completely stuffed - very sloppy, so when i replaced them with new ones, perhaps the vibration was then able to be transferred to the cab (due to a more rigid joint). Because I never felt the vibration previously. So i went to the wreckers and got some old rear upper trailing arms and put them in thinking that might do something, but the vibration was still there.

3.) I thought i might be something weird like the exhaust flexing and causing the whole motor and gearbox to flex, which would put some sort of weid load on the tailshaft, but i took the exhaust off and it is still there.

4.) the vibration doesn't happen in reverse, which makes me think that it has something to do with the diff nose angle putting an axial load on the tailshaft or something, because when you take off, the back end of the car goes down and the diff nose points up. In reverse, the back end of the car goes up, and the diff nose points down.

5.) i jacked up the car from the diff, and put it in drive. The vibration wasn't there. I also loaded it up by holding on the brakes, but the vibration sill wasn't there. It is only when the car is on the ground!!


My next step is to take the tailshaft back in to get the uni's checked. I will also get it balanced, but it doesn't sound like a balancing problem to me, unbalanced tailshafts seem to go through a series of vibration (as the natural fequency's occur i suppose). This problem occurs at its worse when i take off or give it some! and is still present at higher speeds.

Any suggestions will be useful. Thanks.

Chris.

 

[deankdx]

Any suggestions will be useful. Thanks.

Chris.

could the tailshaft be touching the floor? how low is the car?'
falcons when lowered a lot can make the tailshaft rub the floor on accelleration.
i guess you would see marks if so...

somthing a little stupid perhaps, but i had a vibration from my cracked bell housing. although it vibrated in nuetral,the car was very broken at the time, it could be possible i guess
no real clue other than the obvious sorry.

 

[VH 1UZ-FE]

thanks for the suggestions, but it definately is not touching the floor.
Any other takers?

 

[MaxPower]

Got a similar prob with mine (1UZ in a VL), but only a small vibration on take-off under medium to hard acceleration. Tried a number of things and have not been able to track it down, done about 10,000km and its still the same. Prob not what you want to hear!

About the only thing i havn't tried is the adjustable upper trailing arms from whiteline to get the pinion angle correct. My car is lowered but putting it back to standard height made no difference so dunno if these will help.

 

[pops]

vibration

if you had driveshaft disconnected ? take it apart and rotate 180 deg. wheel bearing or axel shaft frozen will also cause problem; look into possible wheel or tire balance.

 

[VH 1UZ-FE]

Got a similar prob with mine (1UZ in a VL), but only a small vibration on take-off under medium to hard acceleration. Tried a number of things and have not been able to track it down, done about 10,000km and its still the same. Prob not what you want to hear!

About the only thing i havn't tried is the adjustable upper trailing arms from whiteline to get the pinion angle correct. My car is lowered but putting it back to standard height made no difference so dunno if these will help.

Max,
This morning, i went to the wreckers and got some coils (original size) and put them in. The vibration has now almost disappeared (about 80% gone). I am over the moon about it. Here's what i think it is.
When i went to put the tailshaft on, it was hard to get the centre mount bracket to line up with the holes under the car. The two piece tailshaft has the ability to slide in and out at the CV, but my tailshaft had no freedom here. Fucks me why, because i haven't made any mods to the cars back end, and it should all be standard still. The car was lowered, which made the diff push forward, which put the back part of the tailshaft in compression. So when i put the higher coils in, the pressure on the tailshafts centre mount was relieved. I think i will get back under the car and have another look to see how much play is there now. If there still isn't much, i will take the back part of the tailshaft in to get shortened 10mm or so.

Thanks for the replies guys, any explanation as to what has caused this will be helpful.

VH.

 

[VH 1UZ-FE]

if you had driveshaft disconnected ? take it apart and rotate 180 deg. wheel bearing or axel shaft frozen will also cause problem; look into possible wheel or tire balance.

I don't think the wheel or tyre balance had anything to do with it. The vibration was too fast to be anything there. It was worse at take off, not at high speed.

I will try the rotating the tailshaft 180°, but the vibration started when i changed the rear upper trailing arms, the tailshaft was not touched when the vibration propogated.

Thanks for the advice.