Regarding the "GRRRR" thread

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Dont worry, im not asking how to fix my GRRR sound after lifting. I know we've been through that one a few times lately. But just one quick question, i do have the grinding noise after lifting and will be adding a front ARB soon, B/c im gonna add a bumper and have a little "stinkbug" look i got some mr gasket 1 inch spacers. after i do the bumper, if i add the spacers will this cause more of a problem with the "GRRR"....thanks, also, if it helps, i am running a the OME heavy springs.

BD
 
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While were at it though, i have read that setting the phase of the u joint out 90 degrees seems to help, How exactly do i change the phase? unbolt and turn the "ears" 90 degrees?

Thanks,
BD
 

Darwood

 
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If your ears aren't already out of phase then yeah do that. If your front drive shaft hasn't been touched before it should already be out of phase. This is the stock setup.

And by turning the ears 90 degrees we mean unbolt the driveshaft, slide the splines apart and reinsert the splines 90 degrees from where they were before.
 

semlin

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hmm, I think I know the answer but I only learned why a few minutes ago. Read the idahodoug Redux thread. Put your drive shaft out of phase if it is not already. Once that is done you have a baseline. I think increased height is likely to increase any driveshaft vibration you have at that baseline. However, this assumes your problem is in the driveshaft in the first place.

Also, you don't say if you have caster corrction bushing installed. That could also improve your vibration situation right now.
 
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Semlin, i do have caster correction installed. Also, if the driveshaft is already out of phase......im guessing there is nothing else i can do with it ?
 
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Darn,

Semlin...the front driveshaft is properly out of phase and the rear is properly in phase. I guess i can cross that off the list of possibilities for my grinding sound.
 

semlin

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you might wish to consider new u-joints and balancing the drive shaft since some trucks do not have a vibration problem with that lift.

You might also consider caster correction plates to overcorrect caster if I am correct in the Redux thread that positive caster will diminish the extent to which the output plates are at different angles and the resulting disharmony. You could even use the caster bushings set backwards to diminish the full effect of the correction plates. I need to study the effects of positive caster on other things like handling.
 

Darwood

 
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I think the correction of caster will actually cause the vibrations to occur more. With the out of phase driveshaft you aren't looking for parallel angles, you are, I think, looking for the same angles. I think the way the suspension in the front cycles provides the conditions that are required for the out of phase shaft. By adding the caster correction the pinion is rotated down which then hurts the optimal angle. I could be wrong. All I know is the out of phase shaft is tricky.

As far as the spacers go, with the added weight on the front I would say if the spacers get the front back to where it was without the added weight the vibration should be the same. If it is higher then the vibration should be worse.

Brandon, I definetly feel for you as I too am trying to battle a driveline vibration. In my case I'm 99% sure it's my rear drive shaft, and the only fix for me is a rear CV shaft. Just last weekend I tried new u-joints in my rear shaft which didn't help much at all with my vibration.
 
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Guys, thanks for the help. i think i will measure how high the truck is now, install the ARB when it comes, if it drops more than the height of the spacers, i will add the spacers w/o too much worry. Otherwise i will probably leave it alone. Before i did the lift i had the classic highway rumble in the 80, it only happened at higher speeds, but like my current problem it was with light pedal pressure or when the 80 was coasting. My new GRRR is kind of similar. Its def not the same but it kinda feels similar enough that it could be from the same source. When i had the old problem i took it in and they said my front ujoints needed tightening and one was slightly bent, they bent it back........Do you think that could be the culprit?

Bd
 
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Brandon

I battled with the GRRRR problem after lift for 6 weeks. I addressed it by dropping the front coils to medium weight (OME851) which solved the grrrrr problem. (well this is not rally a fix, it is just a work around) I then had the stink bug look and added 15mm lift in the front which brought the problem back. I then removed 5mm and the grrr was gone. This lasted for 4 weeks and 3 days ago it is back. sigh sigh sigh. I crawled undernearth the vehicle and found the exhuast clamp on the y-piece to be loose. Replaced it and grrrr is gone again.

BTW: I had a 3.2" lift in the front and 5.2" lift in the rear with castor correction kit.

My guess is that that the problem is the pinion angle but its only a guess to what is causing the problem. But best you check out everything.





And the out of phase propshaft
 
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