GRRRRRRRRR is GONE

[Taz]

Let me give the whole story

Nov 2002
-installed 3" lift with castor bushings
:No vibrations/ No Grrrrrrr

April 2003
-installed front 1.5" spring spacers
:No Grrrrrrr for first 500 miles....very slight Grrrrrrrr started after wheeling in the snow. (grrrrrrr only at 55 mph plus with drive terain at a neutral load)
:No Vibrations

May 2003
-tried a DC drive shaft
:horrible vibrations at speeds between 25 and 65 and grrrrrr still there
-replaced factory drive shaft
"fibrations gone but grrrr still there

April 2003 to May 2005
-no mods made to suspension
:Grrrrrrrrr slightly got worse over the two years although very minimal

May 2005
-installed castor corection plates (replaced bushing with factory)
-installed 1 more inch of rear lift to accomodate extra weight (1/2" gain of lift compared to Nov. 2002 lift height.
:low speed vibrations when accelerating
ver the next couple months the GRRRRR is getting HORRIBLE, very noticable at speeds above 40

November 2005
-remove rear drive shaft (CDL locked)
:Grrrrrr is at its WORST and low speed vibrations
-remove rear drive shaft
:Grrrrrrr not as bad but still there and low speed vibrations

November 2005
-replace rear shaft u joints
:grrrrrr still there and even worse!
:bad vibrations at 25 mph and up
-noticed my mechanic accidently put the rear shaft in out of phase
-reinstalled rear drive shaft so it was in phase
-insalled DC front drive shaft at same time as fixing rear phasing
:Grrrrrr IS GONE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
:low speed vibrations gone!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Wait its not over yet


:now I have a slight vibration at high speeds when accelerating!!!!!!!!!!!
:I also can here a faint high speed ticking noise (new) when slowing down at slow speeds

I am sooooo releived to finally be rid of the grrrrrrr!!!!!!!!

Re-cap.....I should not have re-phased the rear drive shaft and installed the new DC front drive shaft at the same time! Now I don't know which is causing/helping new vibrations and ticking.

I am going to remove my front shaft in the AM to see if the grrrrrrr comes back and the vibration goes away.



I think the moral of this story is....none of this makes sense!!!!
Why did I have the grrrrrrr with the old front shaft removed or the rear shaft removed??? This made me think my problem was in the tranny or transfere case. Now that the grrrr is gone with the new DC front drive shaft and rear u joints none of this makes sense!! I guess the front and rear shafts need each other to balance things out over all?????

My concessus as of today
-DC front shaft is causing slight vibrations at above 45 because I only have 4" lift up front and castor correction plates....too much angle for the DC shaft but not enough for the stock shaft. I am stuck kind of in between.

I have no idea what the ticking could be...maybe the CV in the new DC shaft? or a whole new problem that started by coincidence.

I will post more after removing the front DC shaft in the AM

Sorry song long, I hope this helps everyone with there GRRRRRRRR's

 

[landtank]

I'd suspect that you haven't put enough caster compensation on the front axle to:

1. correct for your caster

2. gotten the pinion angle to where it should be for a DC Shaft.

Just this weekend I added 30mm spacers to my to my front Slee 4" springs. I did this because"

1. the front was a little low, it actually was only 3" of lift

2. my pinion angle was over the acceptable amount for a DC shaft.

That 30mm lift allowed me to add an additional 2* of caster correction to my already 5* for a total of 7*.

The result is a caster around 3* and a pinion angle close to 0*. Now I didn't have any Grrrr before this change but I wasn't going to wait around for it to happen either.

If you have your truck put on an alignment rack and also get that pinion angle read I'm sure you will find yourself needing close to what I've done.

 

[Taz]

Rick, do you have the caster correction plates? How did you adjust your caster?

you only have 3" lift with the 4" springs? what the heck do you have on the front? I've got 4" of lift up front with j springs slee spacers and 10mm packers (ARB/winch/dual bats)

 

[Tools R Us]

Driveline geometry is usually measured in it's static, parked state, because it takes simple tools and an extra degree or so is added to allow for load. It operates in a dynamic, loaded state, when load is applied the rear axle twists the pinion up and the front twists it's down, due to the flex in the bushings, etc., when engine braking they are flexed the other way. When one shaft on an all wheel drive system is removed, the remaining axle carries all of the load, causing more flex, changing the geometry. So removing one shaft is not a definitive test, what your looking for is a change, not always elimination of the noise and/or vibration.

On my truck with about 5" of lift and OME bushings both shafts make minor noise between 50 and 65 mph when freshly greased, if not greased often they make progressively more noise. The front shaft runs slightly quieter in phase, than in the factory recommended out of phase configuration.

 

[landtank]

Rick, do you have the caster correction plates? How did you adjust your caster?

you only have 3" lift with the 4" springs? what the heck do you have on the front? I've got 4" of lift up front with j springs slee spacers and 10mm packers (ARB/winch/dual bats)

I made my own plates for correcting caster. They locate themselves to the original holes in the brackets and then I use a template to drill new holes both front and rear at the desired correction position. My first position was at 5* and then I reworked the plates so I could then redrill them at 7*.

I actually don't have that much weight up front, an ARB with a Hydraulic winch which is almost 100 lbs lighter than the 12k Warn. I haven't measured it but my Hub Center to fender measurement should be around 24.25" now.