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Vibes with new sye and cv driveshaft??

nitrogt101

nitrogt101

NAXJA Forum User
Location
Ventura County, So CA
Some background: 98 sport with d30/8.25, sitting at about 4.5" lift on 31's.

I just picked up my jeep from having 4.56 gears, Aussie lockers f/r, advanced adapters sye, custom cv driveshaft from coast driveline in Ventura, and shortened front driveshaft.

I had a little vibration before all this work, but now it's much MUCH worse. I thought all this stuff was supposed to help vibes? The shop who did the install has a very good reputation from what I've heard. I'm going to call him tomorrow and tell him to see what he offers, but I was wondering if anyone here has any ideas?

I know vibe issues have been beat to the ground, but I could not find anythi g about after sye and cv driveshafts.
 
Did you go to the vendor with a shopping list and money, or did you ask them to determine the cause of your vibration so it could get fixed? If you had a pre-existing problem and did not advise the shop of it, well, then you can't expect the problem to have been addressed by the shop, so think about it and be nice when you talk to the shop.
 
Can you take a picture of the ujoint where your rear driveshaft meets your pinion and post it here? That will help us see your pinion angle and give advice.
 
I am always respectful and nice when I deal with anybody working with any of my property, even if there is a dispute, I deal with it politely.

I went to the shop with all the parts new, he did the gears, lockers, sye, longer coils, and shackles, then measured for a new driveshaft, ordered and installed, and had the front driveshaft shortened to the correct length. He replaced just about every u-joint under the jeep too.

While I did not tell him it was having small vibes before his work, I figured with all the new parts and new driveshaft, new lift, new angles, etc, that it would only be right for him to make sure it is vibe free.

Does it make sense to shorten the front driveshaft after a sye and little boost to the lift? I have never heard of doing that to the front driveshaft to compensate for anything.

I am sure when I call him tomorrow that he will be helpful and willing to look at the Jeep, he has been very generous in helping me out and keeping my build on the "do it once, do it right" path.

I will try to get a picture of it as soon as I can.

Thanks for the help.
 
Well, you have the right attitude.

Why did the front DS have to be shortened? I'm too tired or not thinking straight tonight.
 
If anything, I'd say the front DS would be lengthened, especially after lifting it even more...

Sounds to me like they might not have your rear pinion angle right :dunno: that's where I would start at least....they might not have shimmed your axle properly...
 
Did they check out the front driveshaft to make sure the slip joint is not too worn?

I would try pulling your front shaft and driving around like that.

If anything, the shaft would have needed to be lengthened. I'd say the shaft, now that its shorter, has less spline engagement and is showing the vibes more now.
 
JNickel101 said:
If anything, I'd say the front DS would be lengthened, especially after lifting it even more...

Sounds to me like they might not have your rear pinion angle right :dunno: that's where I would start at least....they might not have shimmed your axle properly...
Click to expand...
X2.

Shot in the dark... you haven't mentioned shims yet. Did they put any shims in to correct rear pinion angle? If they just threw everything else in, and didn't correct the rear pinion angle with shims on the leaf perches, that will cause this problem because the pinion angle goes from a few degrees off to around ten degrees off.
 
kastein said:
X2.

Shot in the dark... you haven't mentioned shims yet. Did they put any shims in to correct rear pinion angle? If they just threw everything else in, and didn't correct the rear pinion angle with shims on the leaf perches, that will cause this problem because the pinion angle goes from a few degrees off to around ten degrees off.
Click to expand...

You know what... he didn't mention anything about doing shims, I will have to ask him about that to see if he did. I snapped some pictures with my phone, I will get them up here soon.
 
Alright, I got the best shot I could at the front driveshaft at the tc, kind of hard to get a good view of it.
photo4-1.jpg

photo2-1.jpg

photo3-1.jpg

photo-1.jpg
 
That's odd, looks like roughly the right pinion angle to me. If you look between the springs and the axle perches from the back of the Jeep you should see some angled shims if he did put them in, or nothing if he didn't. Mind trying to get a pic of that? It'd probably be best looking from about the center of the axle toward one side from the back and slightly above the axle tube.
 
as mentioned above, Check for the shims .

I have never heard of a Front D/S needing to be shortened?
I would remove the front Driveshaft and see if the vibes go away.
 
Looks like the rear pinion is pointing a bit lower than the drive shaft, but its hard to tell from the pictures.

Also, your front pinion angle can be off too.

Also, I have heard of the front shaft being shortened. The more angle on the front control arms the closer the pinion will be to the transfer case. Don't know what control arms he is running, but the control arms could be lengthened a bit to counter act that.

As said, remove front drive shaft and see how the vibes are. Then put front back in, pop it in 4x4 hi and remove rear. See how the vibes are.

Out of balance shafts can cause vibes too. Yes, I know they are new, but I have seen new shafts out of balance. I've had 3 from one vendor that were out of balance new.
 
... which vendor is that? I want to avoid them if I ever actually buy a new shaft.

With an SYE you really do want the pinion a little lower than the rear driveshaft, at least with a leaf spring setup, due to spring wrap. You'll notice the vibrations the most when you are getting on the skinny pedal, which is when the springs will be twisting a bit and the pinion will rise, so it's best to bias a little toward pinion angle being too low.
 
Shortening the front driveshaft is a good idea with a short arm lift if it was close before. The diff gets closer to the t-case as the suspension extends. The pinion angles look good in the pics.
 
i haven't seen anything mentioned about front LCA's, UCA's, or the trackbar.....your pinion looks fine

if your UCA's are original to the jeep, i would replace them (apparently easier to replace entire arm, instead of just the bushings)

is trackbar aftermarket? front axle centered?
 
did you move the vehicle any when you took the picts of the rear drive line? cause if you didnt it looks like the rear yoke is out of sync of the front yoke and that can cause vibs
 
the arrows point at each other in the slip joint, right?

besides that, webdog here in LA was telling me he got a mal-balanced rear d/s from coast... as part of the aa sye 'kit' maybe you got a bad one too?
 
I've just gone through a similar problem on my ZJ. I had some vibration last year with a 242 tc and a double cardon ds with a slip yoke at the tc. I have since installed a 231 w/sye and new ds. I still had the vibration. It started in near 50 mph and increased with speed. I had the ds balanced 3 times by two good shops in Tucson. I finally put it up on stands and had somebody run it at idle in gear. I was able to mark the ds where it was wobbling. It seems that the slip spline was a poor quality and the fit was a little sloppy. He replaced the tube and slip spline. The shaft is perfect now and runs true, but a vibration is still there. Better, but still there. After some trial and error, it was determined that the overdrive is starting to go out. That could explain why I had the vibes last year and are still there after replacing the tc and ds. My vibration showed up when I installed 488 gears. I figure it was there before, but the higher rpms make it more noticeable. You might have the same thing. I will confirm mine by removing the tranny pan and check for metal.

Something to think about!!
 
It seems to me that actually balancing a drive shaft is a fine art. Some can do it some can't. I give Denny's driveshaft's a thumbs up because they were able to give me a balanced shaft after the previous vendor failed 3 times.
 
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