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Using a 90* reference, my angles would be 86.1 (pinion) and 92.4 (DS), so 86.1 - 92.4= -6.3.
if -6.3 represents a number less than 90 degrees ( a pinion flange to driveshaft angle of exactly 90 degrees should net a pinion angle reading of 0) then it would seem your shims would go in front in order to lessen the amount of angle, or make it closer to 0, if I understand what you are saying. Having said all that, I'm actually running a number somewhere in the positive range, as the pumpkin is tipped actually upward in relation to the drive shaft, and I have no issues. I'm not a huge believer in negative or positive, as long as it's a number that's not too much deflected on either side of zero....unless the front ujoint angle is way out of whack.
I watched a video online somewhere where they welded a ring gear on the end of a drive shaft under the in joint and then held a playing card or something against the gear so you could hear it vibrate. Every time they increased or decreased the pinion or ujoint angle the vibration of the playing card would change speeds. The point is that less angle is obviously better. What's interesting though is that all our trucks seem to have this issue at lower speeds than what most folks have when dealing with pinion angle issues. I can't figure it out.
perhaps what is happening is spring wrap at the speeds you mentioned which is enough to throw the pinion angle way out of line for a short duration of time.
Here's a thought: buy a set of the cheap jegs slapper style traction bars and install them to see if it helps eliminate the shudder. I ran them on mine for quite a while before I switched to the VAS traction bars which allow no spring wrap at all. The jegs bars are only like 49 bucks.
another thought would be to see if the shudder happens during moderate to heavy acceleration, and/or if it happens while accelerating very slowly. if it happens while accelerating very slowly, I doubt it would be a spring wrap issue and the traction bars probably wouldn't help.
I installed them because if the roush blower causing all kinds of spring wrap issues on my truck.
Last edited by rojizostang; 06-01-2017 at 04:45 PM.
Yes, the -6.3 is representing less than a 90* angle on the top of the pinion to the driveshaft, so it needs to move nose up to lessen that number, which is inline with putting the tall end of the shim forward.
The shudder is present under very low acceleration, as I noticed it almost immediately the first time I drove the truck around my neighborhood. I haven't gotten on it too hard, as I don't want to stress that joint any more than necessary, but I also feel it on moderate acceleration as I leave my neighborhood onto a 45 MPH road, or every time I pull away from a light in town. I took a short trip on the interstate the other day up to about 85 MPH and never noticed it after the initial acceleration. That said, I don't think it's an axle wrap problem at all.
UNBROKEN, I'm assuming you want to see a pic of the rear pinion, so here it is. I threw in a pic of the truck just because, lol. I can try to get more if there's something else specific you want to see.
Hell man, from that pic yours looks better than mine. lol
The vibration on acceleration is definitely axle wrap. If you floor it at highway speed you'll probably feel it then too.
As far as getting it gone it's looking like you just have "that truck" that you'll have to experiment with. I've had a few I had to fight with that just defied logic myself.
Well, I tried taking the shims out today and the vibration is far worse. I'm still not convinced it's actually axle wrap, as both before and after I can feel it during even the slightest acceleration driving around my neighborhood. After removing the shims I can even feel it when coming to a stop.
I called the only 4WD shop around and they don't stock any shims.
I've got an email in to this company about having a custom set of 5* shims made that have the proper holes and spacing so that I can bolt them into my leaf pack, but I'm not sure what their lead time is. If it's too long then I'm headed to Tennessee on Sunday (not in my truck) and will stop by Summit Racing and pick up a pair of the BellTech 4* (or maybe 6*) shims since they have them in stock and see if that helps at all while I wait on the custom shims.
I got my custom made 5* shims installed yesterday and am happy to report that the vibration is about 95% gone! I hesitate to say it's completely gone, although I'm probably hyper-sensitive to it right now and am not sure if I'd even notice if I wasn't constantly looking for it. They gave me about an extra 1/2" of drop as well, since they essentially act as a block, but thus far I'm happy with the truck is sitting.
I got the shims from a guy at the link below and had them made so that they bolt into the leaf pack and fit properly under the spring perch. Total cost was $57, I ordered them on 6/5 and received them on 6/15, although his website states they may take up to 6 weeks depending on backlog status. http://www.4crawler.com/4x4/ForSale/...ustomWidthShim
If anyone is interested, they're 2.5" x 5" with two 1/2" holes drilled 40mm apart on-center and the center of the first hole spaced 1-3/16" back from the fat end of the shim. They're also steel shims, so no worry about them cracking like the aluminum ones are reported to do.
The shim.
Bolted in place with factory bolts. The front bolt only engages about 2/3 of the threads on the nut, but it should be fine.
The fit on the spring perch, much better than the crappy BellTech shims!
06-01-2017, 04:41 PM
