Front Drive Shaft grrrrrrrrr findings so far. .

[Cruiserhead05]

Romer,

A DC front shaft has cured about 99% of my problems, and i've talked to Concrete, he had good luck as well.

I've read a ton of stuff over and over again on MUD about the lifted 80 driveline issues and not 100% sure my angles are totally setup for the front DC shaft, but i do know that the problem is for the most part, fixed. Although i am itching to put some front spacers in to fix a little stink bug, just not sure if i should take a chance messing with something good.

 

[alkaline747trio]

My assumption on angles w/ lifts...
Here is what a stock setup should look like, correct?



Lifted without correction..



Lifted with caster correction..



It seems that lifted no correction should have vibration issues and poor handling, lifted with propper correction should yeild no vibe issues and stock handling. I'm thinking that with caster back to where it was stock should cause zero problems with vibrations, but it does. What causes the vibrations when the pinion angles should be back to stock?

 

[landtank]

These "/,\ or |" are flanges and "------------" is a drive shaft

In the stock setup the pinion points above the t-case. Pinion \-----------/ t-case

The angles are similar at the u-joints and cancel each other out.

In a lifted truck without correction the pinion still points above the t-case. This is do to the fact that all you did is hinge the axle down. The angles at the u-joints are greater but still similar and a stock shaft will most likely still work.

Now on a lifted truck and correction added by rotating the axle, the pinion begins to drop and point at the t-case |------------/. How well it points at the t-case depends on the amount of lift and the amount of correction. But at some point the 2 converge at the ideal lift/caster Correction to provide proper caster and pinion angle for a DC Shaft. Which is in the 4" lift area.

 

[alkaline747trio]

So my drawings are completely off, ok..now I'm starting to understand this. So what you're saying is that the caster correction rotates the pinion down more in comparison to the t-case than stock to achieve the same amount of caster?

 

[landtank]

yes that is correct. And not enough rotation or too much rotation (depending on lift) can put the axle is a middle zone where neither shaft will work well.

To further complicate this, it is axle dependant. It comes down to the tolerances in the build up of the axle to where this comvergence happens. It's the relationship of the knuckles, diff position and Leading arm brackets in how the are welded together as an assembly that determines this.

This is why some trucks have a high amount of caster and some don't or why some trucks vibrate at a given lift and some don't.

 

[alkaline747trio]

So in some cases you have to decide which, caster or vibration, you can deal with the best without a cut and turn, which nobody seems to be considering.

 

[concretejungle]

yes that is correct. And not enough rotation or too much rotation (depending on lift) can put the axle is a middle zone where neither shaft will work well.

To further complicate this, it is axle dependant. It comes down to the tolerances in the build up of the axle to where this comvergence happens. It's the relationship of the knuckles, diff position and Leading arm brackets in how the are welded together as an assembly that determines this.

This is why some trucks have a high amount of caster and some don't or why some trucks vibrate at a given lift and some don't.

Rick is one smart dude! I totally agree. I found that my front end seems to be in the "middle zone". I found that adding or taking out the Mr. Gasket spacers slightly adds or takes away from the grrrrrrr.

 

[Tools R Us]

The angle that the OME CC bushings are pressed in at affects it too, on rigs equiped with them.

 

[Cruiserhead05]

The angle that the OME CC bushings are pressed in at affects it too, on rigs equiped with them.

Good Point.

Generally speaking i think most who have the CC bushings have someone else install them b/c the need for the heavy duty press.
For awhile i thought this was the case in my front end, that the shop just didnt know the orientation the bushings needed to be and thats why i had problems.

I'm sure its happened.

 

[Riad]

That's why I went a ahead got those drop (hanging and snaggin) barckets from MAF. They sure do correct the caster/camber. I have to live with them until my 3 link is ready. My gut feeling is: Either the tcase output bearing or the pinion bearing has gone bad, in my case. I don't have any leak, absolutle none. As christo said (I think) that your seals for the pinion could be good but the bearing could be bad. Or the DShaft U joints. I wish there was an wasy way to verify which is the calprit. See in my case I don't feel any thing until I am at 60 + mph. In city driving the truck is real smooth. But then when I am going 60 mph at an incline (upword) position I don't feel any thing. That could be the drive shaft but also could the bearings, right?

 

[sleeoffroad]

One thing I do not understand is why people are so reluctant to spend money on u-joints. Hell they are only $40 or so a piece. Most trucks have 100k plus miles on them. When you lift, just replace them with new.

I would speculate that u-joints in most cases are more neglected and worn than birfields, but everyone want to service their front axle, but on-one want to change u-joints as the first step in solving vibrations.

 

[landtank]

One thing I do not understand is why people are so reluctant to spend money on u-joints. Hell they are only $40 or so a piece. Most trucks have 100k plus miles on them. When you lift, just replace them with new.

I would speculate that u-joints in most cases are more neglected and worn than birfields, but everyone want to service their front axle, but on-one want to change u-joints as the first step in solving vibrations.

At the age of these truck, replacing the rear U-Joints should be part of the lift. The front also unless you need a new shaft.

 

[concretejungle]

I agree (except i'm an idiot and for some dumb-a reason let the driveshaft shop manager talk me into shortening my shaft first since he thought it was running "bottomed-out" ). But, the very next thing was ujoints.

 

[Cruiserhead05]

When i first started getting problems, I replaced all the U-joints, in the front and rear shafts. No change at all.

This was very odd though as the factory joints had 255,000 miles on them with somewhat poor maintenance, I would have thought that some type of change would be felt in the driveline.

 

[OGBeno]

One thing I do not understand is why people are so reluctant to spend money on u-joints. Hell they are only $40 or so a piece. Most trucks have 100k plus miles on them. When you lift, just replace them with new.

I would speculate that u-joints in most cases are more neglected and worn than birfields, but everyone want to service their front axle, but on-one want to change u-joints as the first step in solving vibrations.

Best advice I've heard time and again...and it's a pretty easy PM item.

Thanks for reiterating again Christo.
-o-

 

[yep]

Pulled my grrrr'ing front shaft today (drove without it and confirmed it). One axis on both U-joints was good, other axis was pretty worn. I will replace both and see if grrrr'ing stops.

 

[Romer]

Pulled my grrrr'ing front shaft today (drove without it and confirmed it). One axis on both U-joints was good, other axis was pretty worn. I will replace both and see if grrrr'ing stops.

Don't forget to have the shaft balanced

 

[yep]

The new u-joints are in and the drive shaft is balanced.

Even after telling the shop to balance it out-of-phase, they didn't. I unfortunately did not pick it up, and they are closed until Monday.

I am a one-banana guy when it comes to this stuff so here is my question.

Should I install it in-phase (as balanced), take it back on Monday to have it rebalanced out-of-phase, or simply rotate it at the spline and install it out-of phase?

 

[Tools R Us]

The new u-joints are in and the drive shaft is balanced.

Even after telling the shop to balance it out-of-phase, they didn't. I unfortunately did not pick it up, and they are closed until Monday.

I am a one-banana guy when it comes to this stuff so here is my question.

Should I install it in-phase (as balanced), take it back on Monday to have it rebalanced out-of-phase, or simply rotate it at the spline and install it out-of phase?

Try it in-phase, mine runs smoother that way.

 

[yep]

I went with out-of-phase.

No vibes.

I have Grrr... when letting off the gas going around 60.

If I override the overdrive the Grrr. goes away completely.