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Strange vibrations are stumping me!

3K views 24 replies 3 participants last post by  BigSahara 
#1 ·
***Update***

I just replaced the drums with higher quality shoes and now all my brakes are quiet as factory! I also realized my rear sway bar was loose and replaced all the bushings on that and reinstalled. This helped slightly the vibration has gone down but it still exists. The I replaced the rear lower control arm bushings and check the pinion angle. Everything is tight and the pinion seems right on. Problem is I am still getting some vibration when doing about 5-10mph only and not at any other speed. Today I will replace my front lower control arm bushing to see if this helps and remove the skid plate and check the t-case.


***Update***

OK, so the bushings are replaced and the noise is still present. Everything else checked out fine. I'm now convinced I have a more serious problem. One clue though if anyone can help me figure this one out is that my front drive shaft was rebuilt. When it was removed to be rebuilt by someone else a while ago I had no vibes. I got all new the u-joints but could they have been installed wrong? Could the shaft itself have a problem? I have not yet engaged in 4HI yet. Any help on this would be greatly appreciated. Thanks!
 
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#2 ·
***update***

By chance i was pressing directly upwards on the front drive shaft on the end connecting to the transfer case and its moving slightly up and down. Is it a bad u-joint? Is the yoke loose? I have an SYE kit and remember tightening the yoke on the front drive shaft side but can it loosen over time?
 
#3 ·
There are two u-joints and a pin (what is that?) under the boot on the front shaft. You could have a bad u-joint or two in there. Any drive shaft shop could replace both of those and the pin kit for like 150-200.

Does it seem to move in the middle where that boot is or at one of the ends. If it's the ends the only thing holding the shaft are 4 8mm bolts at either end. So if it is the ends, may be something in the front axle or in the xfer case...
 
#4 ·
Ok, well the movement gets more noticeable as I push up on it moving closer and closer to the transfer case. With 4HI engaged its less noticeable. Of course the 4wd pops out while I'm driving all the time so that doesn't help other than the fact that it gets more vibrations when it does. The backlash on the front gears feels normal but when driving at normal speed there are absolutely no vibes with the exception of a very high pitched whining sound that get louder as I pump the gas and then disappears. In any case, I have all new u-joints installed so I am not sure why this is happening.
 
#10 ·
I personally installed my SYE kit with a friend and removed and opened the transfer case. There's not a lot in there except for a chain and the connecting gears. I can't see how anything inside could be loose. I'm hoping it's not that though. It's hard to see up there being that I have not removed my skid plate. Hopefully this can get figured out soon.
 
#12 ·
To help isolate the vibration to the front or rear, I'd probably disconnect the front driveshaft from the front axle's yoke and zip-tie the front of the driveshaft securely up & out of the way so you can test drive it. That you noticed movement in that driveshaft's u-joint area has me a bit concerned, there shouldn't be any movement there at all. That's why I suggest starting by disconnecting the driveshaft at the front so it won't spin while you test drive it.

If disconnecting the front driveshaft cures the vibes, then it's time for new u-joints or perhaps a CV joint rebuild.

For the rear pinion angle, what type of rear driveshaft do you have... the OE or an aftermarket CV? And how is the rear pinion angle set? Is the rear pinion shaft parallel to the t-case output shaft and at an angle to the driveshaft, or is the rear pinion shaft pointing directly up at the same angle as the driveshaft?
 
#13 ·
Thanks for the reply!

I just disconnected the front drive shaft completely! I wanted to see if anything strange was happening up near the transfer case. The joints have all been rebuilt so there's no trouble there. Everything is greased and moves freely with no grinding on both ends and inside the CV. I noticed the female splined end of the shaft has a hair of play in it and that's what was causing the movement I described. Now I started driving it and what do you know, the vibes are still there. Now I'm certain its my Tom Woods CV. I had trouble with trying to reset the pinion angle a few days ago, I don't really know how to do it. I have adjustable upper control arms and fixed lowers in the rear. When I had my gears done I also had the guy fix my pinion angle which, before the SYE, destroyed the yokes, bent the u-joints and the needle bearings were completely missing. I will take a picture of my rear shaft and post it for evaluation.

Thanks!
 
#14 ·
This is how your rear pinion angle should look now that we know you have a Tom Wood (not Woods) CV driveshaft back there...

One more note... the pinion angle should be the same as your rear driveshaft's angle. It can be 1 or 2 degrees lower than that of the driveshaft but it can't be even 1 degree above that of the rear driveshaft.
 

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#15 ·
OK great! Thanks for the diagram. Would you be able to give me step by step instructions on how to actually adjust the pinion angle? I'm having trouble figuring out how to make the rear axle tilt at the the angle your showing.

Thanks
 
#18 ·
Unbolt one end of both upper control arms. Then raise the pinion angle up with a jack under the axle housing where the pinion shaft protrudes out until it's where you want it. Then count the precise number of turns it takes you to lengthen one of the control arms to the right length so it can be bolted back into place with the pinion at the correct angle. Then simply lengthen the other arm by the same exact number of turns and bolt it back into place. :)
 
#21 ·
The splines are supposed to show like that so the driveshaft can expand and compress as needed as the suspension flexes.

Your rear pinion angle looks like it could be just a tiny bit too high... like 1/2 or 1 turn of both of your upper control arms to very slightly shorten them would correct it. As said above, the pinion angle can be equal to or as much as 1-2 degrees under that of the driveshaft but it can't point even be 1 degree above it.
 
#23 ·
Here's the drive shaft after the pinion angle was adjusted. The original length of the upper adjustable control arms were 14''. I had to lengthen then to 13.5'' which seemed like kind of a lot but after they were reinstalled the vibration is
'mostly gone". The vibration is no where near severe, but I may have messed up the u-joints while driving with more vibration for a while. I'm really not sure. I also don't know how these arms were .5'' too short when the pinion angle was set perfectly for them about 5 months earlier. Anyway it's better and I'll keep and eye on the u-joints.

 
#25 ·
It's been over a month now and the vibes are back. I realized after re-reading this post I mis-typed lengthen for shorten...ehhh...which further screwed me up thinking I need to lengthen the Adj. UCA to correct the vibes even though you(Jerry) said to shorten them. At this point the pinion angle is still at the same angle as the transfercase which would mean it's too high. What I really needed to do was shorten them to pull the rear axle forward. I found a link RE Super-Flex2 Adjustable Rear Upper Control Arms - GETAHELMET.COM where the guy says "If the pinion is pointing further down than it was with stock control arms, lengthen the control arms. If the pinion is too high, shorten the control arms". Proof right there. So after my 5th attempt at trying to fix my pinion angle I will post my results.
 
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