Driveline Vibes - searched!

[yossarian19]

OK. I'm running 2.5" higher in my cherokee these days and pick up some minor vibes, 30-38 MPH.
I can
A: Go SYE and spend a ton of money, get a new driveshaft too
B: Go Tcase drop either with washers under the crossmember bolts, a kit, or a Rusty's crossmember.
C: Shim the axle

Cross "A" off the list cause I'm cheap.

With option B, any thoughts / experience as to which is best? I"m thinking new bolts / replacing the studs with longer bolts and stacking 1/2 inch worth of washers to drop the cross member should do it, but will that change the pinion angles enough?

With option C - how many degrees of shim do I need? would 3* do it at 2.5" in the rear? I know there is math involved in this and I'm OK with math but don't have an angle finder of any sort...

Thanks for the help on this, folks - I'm trying to do this whole thing "right" and so far has been a great resource!

 

[TNT]

Buy an angle finder and check your angles, only you can figure out what shim is needed. U-joints don't like changes in ride hieght because they wear in per say to the angle they were at and can cause vibration when a lift is done. If you lower your T-case use a drop kit or build a suitable one, washers are a hack method and should only be used as a test to see if a transfercase drop fixes the problem.

 

[Archdukeferdinand]

Buy an angle finder and check your angles, only you can figure out what shim is needed. U-joints don't like changes in ride hieght because they wear in per say to the angle they were at and can cause vibration when a lift is done.

Definitely have experienced that one, my stock u-joints that were about 100000 mi old vibed like crazy after my 3" lift. New joints and it went away.


As for washers, I don't know about "hack." They'll get the job done, and aren't in concept any different than a drop. Tack 'em together if that makes you feel better, the drop is in effect one big washer.

 

[selarep]

how do you check the angle? what should it be at?

 

[XJ AV8R]

If you are running regular u-joints on the front and rear of the driveline then you don't want to change your pinion angle by inserting angled shims between the spring pack and the axle. 2.5" of lift should not require ANY driveline modifications from stock. Your problem wasn't caused by lifting your XJ 2.5". Something is wrong with the driveline and lifting it has just highlighted the problem for you to fix.

With a driveline using u-joints, the angle of the transfer case output shaft and the angle of the pinion shaft should be parallel. The reason for this is that the rotational velocities of the front and rear u-joints cancel each other out, thus no vibration. Of course, excessive driveline angles CAN cause vibrations, but it would take more than 2.5" to make this happen. I have 3" on my '91 XJ and run regular u-joints without a SYE or anything...it runs great with no vibrations, and has for tens of thousands of miles. The only time that you would want to use pinion shims like you are talking about is when you are using a constant velocity (CV) joint in the front and a regular u-joint in the back. In this setup you would want to shim the pinion angle so the pinion shaft points directly at the CV joint in the front.

Anyway, to fix your problem I would check the condition of the u-joints front and rear. Replace them, if necessary, with Spicer u-joints or better. Cheap crap will wear out fast with the larger driveline angle that your 2.5" lift creates...how do I know this? You might just replace them anyway if they are old, even if they look good...they are relatively cheap.

The transfer case drop will NOT change your pinion angle. The pinion angle is fixed at the axle. You shouldn't have to do this with 2.5" of lift!

If all else fails, remove your driveline and take it to a driveline shop for inspection. My '91 XJ was constantly eating u-joints and began to develop a vibration around 35-45 mph. I finally took it in and the driveline shop found that the weld that holds the yoke "ears" to the driveline on the transfer case end had failed and allowed the two peices to become slightly misaligned, although it wasn't noticeable with the naked eye. The shop cut off the yoke, lined it up, and welded it back on. They also balanced the driveline and put in Spicer u-joints at each end. The total bill was somewhere around 160 bucks (???). It's been a while so I can't remember the exact amount but my XJ has been vibration free for tens of thousands of miles with no u-joint replacements, just a proper lubrication schedule.

In conclusion for this long winded post, check your u-joints or just replace them (don't re-use the straps, btw). I would bet large sums of money that this will fix your problem, but have your driveline inspected as a last resort, particularly if you have done some serious wheeling lately.

Good luck dude.

P.S.- I know there is a post somewhere here on that describes what I am talking about with pictures. I don't have time to reproduce them, but look around a bit...they are here. It is much easier to see the angles I am talking about in a picture format. Later.

 

[TNT]

Definitely have experienced that one, my stock u-joints that were about 100000 mi old vibed like crazy after my 3" lift. New joints and it went away.


As for washers, I don't know about "hack." They'll get the job done, and aren't in concept any different than a drop. Tack 'em together if that makes you feel better, the drop is in effect one big washer.

A flat spacer that spans the mounting surface is the correct way. I have seen one with 3/4" of washers or so get hung up, break the bolts and bent the unibody because the washers concentrate all of the force to a small amount of surface area.

So yes I call it "Hack"..... For a testing to see if a 1/2" or an 1" is needed they are ok, but once you find out what is needed install a real drop kit or build one.

 

[Archdukeferdinand]

So yes I call it "Hack"..... For a testing to see if a 1/2" or an 1" is needed they are ok, but once you find out what is needed install a real drop kit or build one.

Well here's the thing... I've seen lots of "real drop kits" that come with 4 spacers (rubicon express' for example. I have one). 4 cylindrical cast spacers that are almost exactly the same thing as a stack of washers.

While I can see where you're coming from, a t-case drop loses ground clearance regardless of spacer type and that x-member is weaksauce. I don't think either type of drop would hold up to repeated hangs, that's what skids are for.

 

[TNT]

Well here's the thing... I've seen lots of "real drop kits" that come with 4 spacers (rubicon express' for example. I have one). 4 cylindrical cast spacers that are almost exactly the same thing as a stack of washers.

While I can see where you're coming from, a t-case drop loses ground clearance regardless of spacer type and that x-member is weaksauce. I don't think either type of drop would hold up to repeated hangs, that's what skids are for.

There are good and bad drop kits out there, just because Rubicon Express built it doesn't mean its the best design...

I made my own because of that reason. I made a 3/8", 1/2"and a 1" T-case drops all from solid stock about 2.5" wide x 8" long with tapered ends for that reason. I made one other set from 1"x2" 3/16" wall tube with tapered and boxed ends. I use 10.9 grade metric bolts with flanged heads and loctite.

I believe in building my parts whenever possible and designing them the best I can.

 

[yossarian19]

THanks for the advice on using proper spacers instead of washers, folk!
So, I'm hearing that I need to beg borrow or steal an angle finder and determine what degree shims are needed, right? XJ AV8er - are you sure on that, that a stock driveshaft never gets its angle shimmed at the axle?

 

[TNT]

THanks for the advice on using proper spacers instead of washers, folk!
So, I'm hearing that I need to beg borrow or steal an angle finder and determine what degree shims are needed, right? XJ AV8er - are you sure on that, that a stock driveshaft never gets its angle shimmed at the axle?

At 3" of lift on my '94 I use a 3/8" t-case drop, YJ yoke and 2 degree shims for vibration free driving.

On my '95 with 5" of lift I used 4 degree shims, a YJ yoke, a 1/2" longer pinion yoke on my 8.25" and 1/2" t-case drop. This also was good for vibration free driving.

 

[XJ AV8R]

Well, I am just passing on what I have read about driveline geometry. It seems to work for me. TNT says that he has a good setup and he has also changed the angle of the pinion AND the transfer case output shaft to remain parallel. I guess all I am saying is that changing only one and not the other may net you some problems. When I tried to fix my vibes, prior to reading up on this, by adding 2 degree pinion shims at the axle it made the problem worse since my pinion shaft was not parallel to my t-case output shaft anymore. Just my take on it...the pinion shims alone did not help in my case...it actually made the vibes worse. Granted my problem ended up being a faulty driveline, but the shims made the vibes worse until I found the real issue. By the way, I never ran a t-case drop like TNT when monkeying with the pinion angle. If I had then maybe I would not have induced more vibes. Good luck dude.

 

[Boatwrench]

Angle finders are inexpensive, I think mine was like $13 at Lowe's. I have had 5 jeeps (3 of them lifted) and used it on all of them. Get one, then measure the angle of the pinion and then the t/c output shaft. The output shaft and pinion shaft should be within 2*-3* of each other. The angle finder can be placed on the edge of the AW4 trans pan as the mainshaft ad output shaft are aligned. On the 8.25 the housing has a flat boss above the pinion.

I believe to shim the axle & install an SYE is the correct fix not lowering the t-case. Just my belief that lowering the TC case tilts the front of the engine up and stresses the motor mounts.

77CJ with automatic, 3.5 RE kit used 4* shims and double/double cardan shaft
89XJ with a 3.5" RE kit used 2* shims and SYE.
00XJ with 3" OME used 2* shims and no SYE.

Good Luck,
Tom

 

[selarep]

Angle finders are inexpensive, I think mine was like $13 at Lowe's. I have had 5 jeeps (3 of them lifted) and used it on all of them. Get one, then measure the angle of the pinion and then the t/c output shaft. The output shaft and pinion shaft should be within 2*-3* of each other. The angle finder can be placed on the edge of the AW4 trans pan as the mainshaft ad output shaft are aligned. On the 8.25 the housing has a flat boss above the pinion.

I believe to shim the axle & install an SYE is the correct fix not lowering the t-case. Just my belief that lowering the TC case tilts the front of the engine up and stresses the motor mounts.

77CJ with automatic, 3.5 RE kit used 4* shims and double/double cardan shaft
89XJ with a 3.5" RE kit used 2* shims and SYE.
00XJ with 3" OME used 2* shims and no SYE.

Good Luck,
Tom

So in this picture, where would I be measurung the angle? the red part or the blue part?

 

[Boatwrench]

Red part.

 

[Rod Knee]

Well, I am just passing on what I have read about driveline geometry. It seems to work for me. TNT says that he has a good setup and he has also changed the angle of the pinion AND the transfer case output shaft to remain parallel. I guess all I am saying is that changing only one and not the other may net you some problems. When I tried to fix my vibes, prior to reading up on this, by adding 2 degree pinion shims at the axle it made the problem worse since my pinion shaft was not parallel to my t-case output shaft anymore. Just my take on it...the pinion shims alone did not help in my case...it actually made the vibes worse. Granted my problem ended up being a faulty driveline, but the shims made the vibes worse until I found the real issue. By the way, I never ran a t-case drop like TNT when monkeying with the pinion angle. If I had then maybe I would not have induced more vibes. Good luck dude.

Did you shim your pinion down (fat side of shim forward) or up (fat side rearward)?

 

[TNT]

Did you shim your pinion down (fat side of shim forward) or up (fat side rearward)?

I had to shim it with the thicker part forward.

 

[TNT]

THanks for the advice on using proper spacers instead of washers, folk!
So, I'm hearing that I need to beg borrow or steal an angle finder and determine what degree shims are needed, right? XJ AV8er - are you sure on that, that a stock driveshaft never gets its angle shimmed at the axle?

For starters you should replace the u-joints because they are running at a steeper operating angle.

Check your angles and set the pinion angle 1 degree lower then the transfer case angle.

You shouldn't need to drop your transfer case for the amount of lift you have.

I would suggest you buy a YJ yoke to replace your stock yoke. The stock one will bind at about 2" of droop more than stock.

If you have any questions just ask.

 

[WholeLottaXJ]

I'm trying to do this whole thing "right"

Personally, I think you answered your own question. The only "right" way to do it is to go ahead and do the SYE. You'll be much happier in the long run. Chances are that you'll want to go higher someday, so you're going to have to do it anyway. I'd say to spend the money now and get it done correctly, never to worry about it again.

 

[yossarian19]

On the SYE: Clearly a H&T is a great way to go, and if I can possibly avoid spending money that I don't actually have then I am going to do it. I'm 23 & not into real estate - need I say more?

On measuring the angles: I think I get the notion of how to position the angle finder. I'm less clear on exactly what to read off of though -
with my doohickey braced against a spot on the axle perpendicular to the pinion yoke (like the housing when the cover is off) I am measuring the angle of exactly what?
And where?

Angle of driveshaft in relation to pinion? Is that what I'm getting, here?

Lord - every project is a new education...

 

[pierceME311]

Here are a couple great webs sites and good reads. You should go to your local u-pull-it and pick up a front driveshaft from an auto trans XJ and use that for your rear for the time being. I did it and many other have. Next time you get stumped on a problem try google also because there actually is alot of XJ tech out there you just have to look hard enough. these two should serve you well, also visit Tom Woods website because he has a whole section on droveline 101. I shure hope after all this you have a good idea of what your doing, alot of people have stepped up to help you out. Do it to it!

http://www.4xshaft.com/index.html

http://www.4x4getaways.com/oldmansye.htm

http://www.yuccaman.com/jeep/sye.html