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Discussion Starter #1
After having some driveline vibration issues after my 2" Lift I fitted a pair of Adjustable Upper Trailing Arms, I started by making them 5mm longer than the centre to centre dimension of the original fixed length trailing arms. This made very little difference, the vibration was still there but slightly quieter. I then increased them a further 5mm in length and there was a noticeable difference, not completely eliminated but a big improvement.

So after a 10mm increase in the length on the Upper Arms I got a result which nearly eliminated the vibration.......BUT.....after a couple of weeks letting everything settle in, it's back, not as bad as the initial problem but it's not sorted.

Am I correct in thinking when I had my 2" lift that the rear diff would have dipped forwards, as in to say it "rotated forwards towards the front of the vehicle".....? Should the Upper Trailing Arms be increased in length to push the diff back, as they are mounted to the top of the rear axle it kind of makes sense......?

Is it correct to keep increasing them until the vibration stops, I didn't know if 10mm was that much or not.

Any clarification would be welcome

Cheers

Johnny
 

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Thanks In Advance
nissan
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The diff rolls backwards, so they need to be made shorter which corrects the pinion angle and also straightens the springs back up as they would have started to curve also, but it is not that noticeable with a 2" lift and adjustable uppers really arnt necessary. I would say its a problem elsewhere causing the vibration
 

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Discussion Starter #4
Did ya get the vibration all the time or at a certain speed/rev ?
At certain speeds, was around 70-110km/h originally and now the adjustable arms have been made slightly longer its come down to around 60-90km/h.

Looks like I've been adjusting them in the wrong direction as well.

Thanks

Johnny
 

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Discussion Starter #5
The diff rolls backwards, so they need to be made shorter which corrects the pinion angle and also straightens the springs back up as they would have started to curve also, but it is not that noticeable with a 2" lift and adjustable uppers really arnt necessary. I would say its a problem elsewhere causing the vibration
I'm adjusting them back to the standard length this afternoon then I'll go 10mm shorter and see if that makes a difference. If it doesn't I'm not sure what else to look at, it takes off fine, no juddering or slipping. It selects and operates in Hi & Lo just fine, all brakes have been checked and new wheel bearings inners & outers up front.

Any more suggestions greatly appreciated.....

Thanks
Johnny
 

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GQ Dual Cab. TD42Ti with fruit.
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Get yourself an angle gauge mate, then you can set the pinion angle to match the transfer output without guessing. Have a look on ebay, I bought one for about $13.
 

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Discussion Starter #7
Get yourself an angle gauge mate, then you can set the pinion angle to match the transfer output without guessing. Have a look on ebay, I bought one for about $13.
Yep, I picked one up but as I wasn't doing the UJ's I just switched the Upper Arm's and adjusted. This time I'll take the advice and drop the drive shaft and get both faces parallel. Am I correct in thinking once they are parallel I should slightly adjust the arms so that the rear diff face drops by 0.5 degree or so....so that when under load when driving it lifts back parallel.....? I'm sure I'd read someone on the forum advising to do that....???

Thanks again & Merry Christmas

Johnny

P.S. - Once sorted I'll post to inform others exactly what I've done to correct it.
 

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My understanding is that you are correct. Set it parallel by the gauge and then experiment to get the best result.
 
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