A couple of driveline questions. - JeepForum.com
 
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post #1 of 9 Old 09-25-2017, 11:45 PM Thread Starter
NordicYeti
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A couple of driveline questions.

So I've been dealing with some pretty bad drive-line vibrations since I've owned my xj, and now that I started commuting alot more I've decided to tackle the issue. The vibes start getting bad around 55, and at 75 mph it's a pulsating deep vibration that rattles the coins in my ash tray. I'm not thinking it has anything to do with the front end, as I don't especially feel the vibes through the steering wheel. If anything, the vibes seem to come from below me. Also I'm not thinking it's the driveline angle, as the PO had the rear axle properly shimmed and the jeep has a hack n tap sye. I'm sitting at 4 inches of lift currently. Besides, I also did a t case drop and this didn't really help, maybe just changed the vibes a little bit.

So anyways, I'm thinking that it's probably something to do with the drive shafts, possibly worn u joints? Lately I've had a bit of a popping sound/vibration when starting from stop and when slowing till stop, under 10 mph, so I'm thinking this could be evidence of a bad u joint as well.

Now, I visually inspected the axles and yanked em around a bit but didn't seem to get any play from any of the u-joints, and nothing looked especially out of wack. How else could I go about figuring out where the problem might lie? Seeing as I have a sye in the rear, I can probably pop the rear driveshaft out, go for a drive, and see if the vibes stop, and if that doesn't work, pop the front out as well and see if that does anything (after putting the rear back in of course )?

On another note, I've heard that you can run a stock xj front driveshaft in the rear if you have an sye and some lift. This would probably be a bit more economical and easy for me than rebuilding the rear with all new u joints and centering yoke. Anyone know anything about this? It was a bit unclear because the guys running it all had a great deal of lift. Also someone said something about having to get longer bolts to attach the driveshaft?

Thanks in advance!

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1997 XJ 4LI6
4.11 Gears Chrysler 8.25
4.5 Lift Bilstein 5100s
33/12.5/15 Duratracs
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post #2 of 9 Old 09-26-2017, 10:50 AM
livnlrn
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I had some vibes alot like you are describing after I lifted mine. It was the front shaft. After adjusting the front pinion angle, everything is fine. All vibration gone!

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post #3 of 9 Old 09-27-2017, 01:08 PM
ShawnAtTomWoods
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Did your vibration start happening immediately after making some sort of change to your jeep? For example, right after doing the SYE, or right after changing the joints in the shaft, or something like that? Or is the vibrations something that has developed over time and continues to get progressively worse? If it is something that has developed and continues to get worse, that almost certainly means that something is wearing out. Grabbing things and shaking them is an excellent way of finding loose/worn parts. However, if the drivetrain is under load, things may feel tight when they really are not. The best way to do it is to chock the wheels so the jeep doesn't roll over your legs, put the jeep in neutral, then crawl underneath and look for loose joints.

Another possible cause could be that whatever the driveshaft is attaching to is bad. For instance, if the yoke on the transfer case is a little wonky it will cause the drive shaft to run off-center and cause vibrations. I had a customer last week who had driveshaft vibrations with a new drive shaft, not our shaft, but a new shaft all the same. He had a SYE made by a company who is known more for low prices than high quality. So because it's an easy and inexpensive place to start, I suggested that he replace the output yoke on the transfer case and see if that fixed it. He called me back a few days later and told me that it completely fixed the problem.

As for using a stock xj shaft on the rear, I recommend against it. There are a couple of reasons for this. The first and biggest reason is just that any stock front xj shaft is old, and probably rusty, and probably worn out. Another is that the front shafts are not quite as robust as they should be for a rear shaft. The rear shaft does most or all of the work most of the time and needs to be a bit stronger and in better condition than the front shaft. Finally, you can get a brand new rear shaft for less than $300. Often people will invest $200 into making a sub-par stock front shaft work.

Shawn Wood at Tom Wood's Custom Drive Shafts.
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post #4 of 9 Old 09-27-2017, 01:18 PM
BlackFly
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First isolate the culprit. Remove the front shaft first and see if it goes away.
One main XJ vibe source is a badly worn pinion yoke. The insides of the little tabs that center the u-joint get worn back so the caps can shift off center. The yoke should have crisp sharp edges and a new u-joint should fit tight between the tabs.
The other is the blue lining in the slip joint of the front shaft is long gone, making it real clunky when extended out. ....and that's where it is riding at if you're at a 4" lift.

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post #5 of 9 Old 09-27-2017, 07:23 PM Thread Starter
NordicYeti
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So I ended up inspecting the rear drive shaft again, and noticed that there was no grease fitting in one of the U joints. Took the rear drive shaft out, and with only the front driveshaft in there are no vibes!

So, I'm attempting to do a rebuild of the driveshaft, but I've run into a bit of an issue. My sye yoke is not a standard yoke, but a flange. So rather than buying a standard centering yoke, I'm going to need to buy a flange style centering yoke. Unfortunately the centering yoke part number that was on there is pretty unreadable, but it looks like it begins with C8 and ends with 3 eights, nines, threes, or some sorta combination of those three numbers. I'm assuming that the Dana Spicer 211229x is the part I'm needing, right?

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1997 XJ 4LI6
4.11 Gears Chrysler 8.25
4.5 Lift Bilstein 5100s
33/12.5/15 Duratracs
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post #6 of 9 Old 09-27-2017, 10:58 PM Thread Starter
NordicYeti
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Went ahead and started breaking down the driveshaft. Cleaned it up a bit and the part number I got from the flange centering yoke is C2-3-388. Google search returned no hits, weird right? A part from Neapco N2-83-388X was the only thing that popped up, and it looks to be the right part. Also, the Spicer 211229X Socket Yoke Assembly has the exact same specs as the Neapco. Seeing as a could get the spicer off amazon for not only cheaper than the Neapco, but also with two day shipping, I went ahead and ordered that.

Now, tearing down the driveshaft, the u joints were actually not too bad. Even the one missing the grease fitting wasn't bad, no dry spots or rust, grease just looked a little old and crappy. Now the centering ball thingy, on the other hand, was HORRIBLE. Totally shot, there where actually curled up needle bearings in the cup that holds the ball. Only thing I'm worried about now is that the post that sticks out from the driveshaft and into the centering ball might be worn out; it looks physically ok but I guess I'll just have to wait and see.

This is probably a stupid question, but when I go in to get the driveshaft re-balanced after I rebuild it, It's supposed to be ON the vehicle, right? I can't just take in the driveshaft by itself?
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post #7 of 9 Old 09-28-2017, 10:44 AM
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Quote:
Originally Posted by NordicYeti View Post
Went ahead and started breaking down the driveshaft. Cleaned it up a bit and the part number I got from the flange centering yoke is C2-3-388. Google search returned no hits, weird right? A part from Neapco N2-83-388X was the only thing that popped up, and it looks to be the right part. Also, the Spicer 211229X Socket Yoke Assembly has the exact same specs as the Neapco. Seeing as a could get the spicer off amazon for not only cheaper than the Neapco, but also with two day shipping, I went ahead and ordered that.

Now, tearing down the driveshaft, the u joints were actually not too bad. Even the one missing the grease fitting wasn't bad, no dry spots or rust, grease just looked a little old and crappy. Now the centering ball thingy, on the other hand, was HORRIBLE. Totally shot, there where actually curled up needle bearings in the cup that holds the ball. Only thing I'm worried about now is that the post that sticks out from the driveshaft and into the centering ball might be worn out; it looks physically ok but I guess I'll just have to wait and see.

This is probably a stupid question, but when I go in to get the driveshaft re-balanced after I rebuild it, It's supposed to be ON the vehicle, right? I can't just take in the driveshaft by itself?
Yes, 211229X is the part you need. The numbers on the yoke are just casting numbers and not actual part numbers. The brand of yoke will not matter as long as it is the correct flange pattern. Neapco and spicer are both very good brands.

The centering pin, the little cylinder that the ball rides on is an important part. It needs to be smooth and uniformly cylindrical. If it is tapered, or has grooves in it, it is bad and needs to be replaced. Unfortunately, it is part of the cv weld yoke, the part that welds to the tube. So to replace it, you would have to bring it to a reputable drive shaft shop. That is the point at which you may spend as much or more to repair the old shaft as you would to buy a new one. If you have calipers and want to check, the pin should be exactly .500" in diameter. A couple thousandths of an inch smaller is okay.

You also mentioned that you have a flange on the t-case. This could mean that you have a hack and tap SYE. These are types of SYE kits are very vibration prone.

Yes, once the shaft will need to be re-balanced. But no, it should not be and really can not be balanced while in the vehicle. You will want to bring the shaft itself to a drive shaft shop for balancing, no jeep required.

I hope that helps!

Shawn Wood at Tom Wood's Custom Drive Shafts.
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post #8 of 9 Old 09-28-2017, 11:33 AM Thread Starter
NordicYeti
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Hey thank you very much for the reply. Good to know that the part is the same and should work. Thanks for clarifying on the balancing question.

Unfortunately, I don't have calipers to measure the stud, but it looks fairly good; not tapered or rough; looks pretty smooth actually. That being said, it'd probably be best to figure out a way to get it checked before putting the whole thing back together.


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1997 XJ 4LI6
4.11 Gears Chrysler 8.25
4.5 Lift Bilstein 5100s
33/12.5/15 Duratracs
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post #9 of 9 Old 09-28-2017, 11:53 AM
ShawnAtTomWoods
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Quote:
Originally Posted by NordicYeti View Post
Hey thank you very much for the reply. Good to know that the part is the same and should work. Thanks for clarifying on the balancing question.

Unfortunately, I don't have calipers to measure the stud, but it looks fairly good; not tapered or rough; looks pretty smooth actually. That being said, it'd probably be best to figure out a way to get it checked before putting the whole thing back together.


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If it looks smooth and not tapered, then it is most likely good.

I have attached a photo showing an old yoke with what is still a good pin for reference.
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IMG_20170928_114211.jpg  

Shawn Wood at Tom Wood's Custom Drive Shafts.
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