Diagnosing new vibe, solid driveshaft the answer?

So I've had my lift on for probably 2 years, roughly 30,000 miles. I've had the takeoff shudder that is so common, but that is the extent of the vibes that I've had with exception to some vibes while braking at highway speeds. I've experimented with some 1/4" spacers on the carrier bearing which did help. I then worked with Beefed Taco on his carrier bearing drop bracket, which further helped. Basically I could reproduce the take-off vibe if I tried, otherwise is was pretty much non-existent.

The other day I was driving and I noticed a brief vibe/shudder, going just under 35mph. I thought it was just the road, but I reproduced it a few more times, enough to realize it was coming from the rear and was infact some other sort of vibration. Here is what I've done to troubleshoot, looking for other ideas, suggestions, thoughts?

- Greased all 5 zerks on driveshaft, everything felt pretty tight along the driveline.
- Torqued u-bolts to 75ft/lbs, all were right on, no loose bolts noted.
- Removed Beefed Taco's CB drop. Take-off shudder more visible, vibe b/w 30mph and 40mph is still there depending on conditions (hill, foot on gas cruising vs coasting, etc).

One thing to note is that with the Beefed Taco CB drop, braking from 70mph down to 60mph, my steering wheel would shake a bit like a wheel out of balance. It was enough that if I knew it was a wheel, I'd take it back for a rebalance. After removing the CB drop, that shake is gone, the vibe while braking is much tighter and much less.

I've researched the bajesus out of shims, a Tom Woods drive shaft, etc. Sounds like a TW shaft might be the answer, but without knowing for sure, I'm having a hard time pulling the trigger. For proper angles with the factory driveshaft, it seems as though the pinion needs to be parallel with the output shaft from the transfer case, sound accurate? I haven't verified this quite yet. If this is true though, I want to say that I need to install some small shims with the large side towards the front..???? Installing shims with the fat end at the rear would rotate the differential up, making it point at the CB.

Thanks for any input!

-STLTaco09

 

Probably important that I mention that I have a 2009 DCSB TRD Sport 4x4. Bilstein 5100's all around, fronts at 1.75", TSB leaf pack in the back, with Toytec AAL.

 

Have you ever had a U-joint replaced? I'd take it in and get the shaft balanced for shits and giggles, it isn't usually that expensive.

I'd also inspect your carrier bearing, make sure it isn't slowly wearing out.

 

I've not had a U-Joint replaced, only 40,000 miles on the truck. I started looking down that road but without some heavy wear and tear, it seems that this is low mileage for U-Joint replacement.

 

That is pretty low. I had one go out around 60k. I've rarely heard of anyone with over 2 inches in the back not having some sort of vibration. You could also look at axle shims too, they're a possibility.

You keep saying its coming up while braking though, you sound knowledgable, but are you sure you don't possibly have warped rotors?

 

The vibe I described while braking is just another one, not the one in question here. The one I'm concerned about is the 30-40mph one, which was never experienced for about 30,000 miles until just last week. So in my mind, something has changed, wearing out, loose, etc.

I thought about shims, but in researching the optimal pinion angle for the stock driveshaft, I can't come to terms with which way it needs to be shimmed to that is aligned as it was designed to be use. Typical use is fat end in the back, which would rotate the pinion up. But That would point it more towards the CB. From what I understand, this shaft with the CB is designed to be run like the diagram on page 14 here:

http://www2.dana.com/pdf/J3311-1-HVTSS.PDF

 

Rotation the pinion down would only create more of an angle. Rotating it upward would alleviate the angle, and with the aid of the carrier bearing shim, you should be able to match the angles. This is all just going off of what I'm reading in your manual you posted here.

 

Guess it all really depends on how far the diff is currently angled. Is it pitched up from the factory?

Any other ideas on this new vibe that has creeped up? I'm working on getting some steel shims from 4crawler.com, with new centering pins. What degree of shims would be good to start with? I've seen Chris4x4 recommend 2.5* pretty often.

 

Your thinking on shims matches my own.

Lift puts driveshaft out of spec for running angles, but most manage it OK with some minimal vibration.

If something's changed, maybe rebalance the driveshaft?

 

Bump

 

Went ahead and ordered some new steel shims from 4crawler.com. Went with 2.5* shims (2" wide x 4.75" long, based on some rough measurements), along with a new set of 3/8" x 5" long centering bolts. We'll see what this does, I also have 1/4 CB drop spacers and the original one from Beefed to play with. Hoping this takes care of it.

 

Just for som info - when I did my lift several years ago, I got a vibe at about 20-40 under acceleration. I didnt give it much thought and went to a Tom Woods 1 -piece. It got rid of my vibe and has since (about 5 years now).

When I put my crawl box in, they even shortened it for me for like $40 and rebalanced it and shipped it back for free within a week. Even now with it 8" shorter - still no vibes.

 

Thanks for the info. Which driveshaft did you go with? Standard style or the Double Cardan?

 

Just standard style.

 

Did you have to shim at all?

 

nope - never had, the one piece just worked out fine for me.