Front DC drive shaft vibration:

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-Spike- said:
Your driveline angles are changing as you get on and off the gas. A little extrapolation will tell you which direction your angles need to change, based on what's happening when you accelerate and decelerate.

I wonder why you would make more changes (adding height to the front) before you remove the rear shaft and check that scenario out? When troubleshooting, it's always best to make as few changes at a time as possible, fully exploring the ramifications of each modification before adding more factors to the situation.

-Spike
Click to expand...

Makes all kinds of sense Spike. Because I can't do my own I'm kind of at the mercy of others (like the gears being installed 2-hours away :mad: ). I did the lift to correct the front angle per Slee and Rick.

I just picked the truck up. I like the added inch look. He did grease my rear shaft. It took a good amount of grease he said.

Vibration-wise, doing this smoothed the truck out a lot at 50+ MPH. It actually is a doable trip-mobile BUT there is vibration left and it's still bad at 40-50MPH.

OK, my mechanic (and me) doesn't have time to play with drive shafts today, so, I thought I'd post my driveline angles for you-all to review. Our next plan is to play with shafts though somebody might point out an issue with the rear pumpkin angle. In fact, from what I'm learning here it does look like that pumpkin front needs to point more downward. It looks like it's angling upward? What do you all see? THANKS!

54495045-M.jpg

54495049-M.jpg

54495050-M.jpg
 
The front looks good. The rear driveshaft looks great, if you had the DC rear shaft. It definitely should be pointing down more. Get out there with a angle guage and tell us what the angles are.
 
Darwood said:
The front looks good. The rear driveshaft looks great, if you had the DC rear shaft. It definitely should be pointing down more. Get out there with a angle guage and tell us what the angles are.
Click to expand...

I've got a protractor. What do I measure?
 
Measure the vertical angle of both tx case flange and the diff pinion flange on the rear.

If the greasing helped, it is a pretty good indication that you are also dealing with worn u-joints and slip.

Also, just fyi, do not neglect to grease the double cardon joint on the front drivehaft. Every 3k miles, otherwise it will fail. You need a grease gun with a needle fitting to do that.
 
Crap....can't find the protractor. I'll head to my mechanics late today.

I looked at the flanges...the T/C rear flange points downward toward the ground a few degrees. The rear diff flange points opposite (upward) about the same amount.

IF, they are off from being parallel to the ground by the same degrees, are they correctly aligned?

Or, since the T-case flange points DOWN by x-degrees should then the rear flange also point DOWN by the same x-degrees? Cuz right now it points UPward.
 
You want the outputs of the transfercase and the pinion to be parallel. So yes they should be identical angles. If the transfercase is pointed down a bit the pinion should point up a bit. If the transfer case points up a bit the pinion should point down a bit. The thing is I seem to recall that the output on the transfercase points up a bit, not down. I could be remembering wrong though.
 
Darwood said:
You want the outputs of the transfercase and the pinion to be parallel. So yes they should be identical angles. If the transfercase is pointed down a bit the pinion should point up a bit. If the transfer case points up a bit the pinion should point down a bit. The thing is I seem to recall that the output on the transfercase points up a bit, not down. I could be remembering wrong though.
Click to expand...

Yes, since the TC points downward and the rear flange upward the two lines are pretty-much parallel.

So I need to measure this and re-adjust the rear uppers arms until completely parallel?
 
I agree that the rear looks pretty good but for the front I can't tell from that angle, you really need a pic horizontal to the drive flange on the front to see it well enough.

Also you should measure from the tires to the frame to get an idea how centered the truck is. As you lift it the axles get pulled to one side which will also cause pinion angle issues which won't be detected by the simple protractor check.

Last, the front is a relationship between the drive flange on the diff and the drive shaft itself when checking for a DC shaft. Just didn't want you to wig out if you ran the same test on the front as the rear.
 
landtank said:
I agree that the rear looks pretty good but for the front I can't tell from that angle, you really need a pic horizontal to the drive flange on the front to see it well enough.

Gotcha. We'll do the nest round of checks and re-pic the front.

Also you should measure from the tires to the frame to get an idea how centered the truck is. As you lift it the axles get pulled to one side which will also cause pinion angle issues which won't be detected by the simple protractor check.

Last, the front is a relationship between the drive flange on the diff and the drive shaft itself when checking for a DC shaft. Just didn't want you to wig out if you ran the same test on the front as the rear.
Click to expand...

Gotcha. We did the panhard adjusts and he centered the axles though I HAVE NOT MEASURED. I'll do that.
 
Darwood said:
You want the outputs of the transfercase and the pinion to be parallel. So yes they should be identical angles. If the transfercase is pointed down a bit the pinion should point up a bit. If the transfer case points up a bit the pinion should point down a bit. The thing is I seem to recall that the output on the transfercase points up a bit, not down. I could be remembering wrong though.
Click to expand...

Actually the angles need to be the same on both sides of the shaft. Parallel is just one such a case. \----/ or /-----\ is good to as long as both angles are the same. This is for a shaft with single u joint on each side.
 
landtank said:
FYI. centered is while on the ground, not on the lift.
Click to expand...

Ah....hmmmm....I wasn't there. Good point. I wonder if he checked when back on the ground? Yer good. You done a few of these? :D
 
OK, THE REAR DRIVESHAFT IS OUT!

Here's what we found.....

TCase U-joint...felt OK throughout it's range.

Rear U-joint rotated easily within half of it's range. Rotates and twist on the outside angles and it's much tighter. It has worn unevenly.
Our diagnosis....bad U-joint

TEST DRIVE WITH FRONT SHAFT IN ONLY:

Vibration less for sure though it's still there when on the gas and cruising. The higher the speed the more you feel. When off the gas or slowing down it's pretty smooth. That bad spot at 35-45 is still there. This bad area must be the front issue/shaft.
Our dignosis....rear shaft was a culprit though something is also wrong up front.

Our plan...unless I read otherwise:

1. Replace both U-joints on the rear shaft.
2. Install and adjust arms for smoothness.
3. Have front DC shaft tested out. Though new it could be bad.
4. Other ideas on the front end? My front lift amount is 23 7/8 from center wheel straight up to fender.
 
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