Now I've done it (NP231 problems)

[kootenayXJ]

Hi all, long time (over 10 year) user of but my user name was reset a few years ago. Hoping you all can help me out as you've done in the past many times. I've owned 3 XJ's over the years, and having done everything from replacing leaking rear main seals to installing new pushrods, several lift kits etc I consider myself fairly competent but I have zero experience with the transfer case so please bear with me.

simple questions about my NP231 and a SYE

I recently (less than 500 miles ago) installed a 2.5" lift on my 2000 XJ with NP231/NV3550 5spd.

After the install I checked my driveline angles and adjusted the pinion angle to within .3* of the output on my transfer case. I know this wasn't perfect but I thought it was "close enough". After driving around for a few days I was getting some driveline vibrations between 30-45mph, below and above that (up to 90mph!) was smooth as stock so I decided to live with it for a while before deciding if I should drop the TC or pony up for a SYE.

Anyhow, fast forward to today, notice the driveline vibes have gotten worse. I crawl under and find the tailhousing is spewing fluid and there is around 1/8" play in the front most u-joint which is felt in the the slip yoke and into the tail housing as well. If I grab the stock slip yoke, I can push it up and down around 1/8"-3/16" and hear it moving inside the tailhousing.

So, what have I broken exactly? I guess I'll be springing for a SYE and repairing the damage I've done, but can someone please tell me where to get started to I know what I'll be rebuilding?

Many thanks!

 

[md21722]

Its possible your u-joint was marginal before and changing the operating angle destroyed it. It also sounds like the output shaft bearing was destroyed. Its surprising because a 2.5" isn't that much of a lift. The SYE kit replaces the stock output housing and comes with a new bearing. Check out Advance Adapters or Novak Adapters websites or the FSM for instructions on how to tear down the transfer case. Also look at some videos. It isn't that complicated. The special tools needed are a good pair of lock ring pliers (Sears, $15) and a 10mm 12 point socket. If installing a SYE, you'll also need an angle meter to properly set the rear pinion angle and typically a 28mm, 29mm, or 1-1/8" socket depending on what yoke nut is shipped. Consider replacing the chain if there is excessive slack, shift fork pads, and front output bearing/seal while you have it apart. But first check it out and see what happened.

 

[shelbyluvv]

Your rear pinion needs to be on the same plane as the transfer output. You really should not of had any reason to mess with the pinion angle at 2.5" of lift.

I think your issue was self inflicted.

 

[kootenayXJ]

Your rear pinion needs to be on the same plane as the transfer output. You really should not of had any reason to mess with the pinion angle at 2.5" of lift.

I think your issue was self inflicted.

After installing the lift I used an angle finder to check the angles on the transfer case output and the rear pinion. I found they were just over 1* out from each other so I installed 1* shims to bring them back even, now the angles sit within .3* of each other. Should I not have done this?

Everything I have read online points out that I should shim the axle to bring the pinion level with the output, so that's what I did. Some people recommend lowering the pinion angle 1-2* below the t-case output to account for torque, which I didn't do, so maybe thats where I went wrong.

I'm going with the idea the front u-joint was already on its way out and has now completely died and taken out the rear output shaft bearing as well..but what do I know? In any case I'll need to order a SYE in the next few days here and get to it.

 

[kootenayXJ]

Its possible your u-joint was marginal before and changing the operating angle destroyed it. It also sounds like the output shaft bearing was destroyed. Its surprising because a 2.5" isn't that much of a lift. The SYE kit replaces the stock output housing and comes with a new bearing. Check out Advance Adapters or Novak Adapters websites or the FSM for instructions on how to tear down the transfer case. Also look at some videos. It isn't that complicated. The special tools needed are a good pair of lock ring pliers (Sears, $15) and a 10mm 12 point socket. If installing a SYE, you'll also need an angle meter to properly set the rear pinion angle and typically a 28mm, 29mm, or 1-1/8" socket depending on what yoke nut is shipped. Consider replacing the chain if there is excessive slack, shift fork pads, and front output bearing/seal while you have it apart. But first check it out and see what happened.

thanks for the advice. I agree that the u-joint must have been marginal beforehand as I've installed the same size lift in both my previous jeeps (1990 & 1998 XJ's) with no problems. After reading a few tutorials it doesn't look like a bad job.

Now, (and I'm in the midst of searching), I just need to figure out what kind of junkyard shaft I can use with my NV3550 after the SYE. Sounds like a regular Auto XJ front may be too short.

 

[cal]

its pretty common to get vibes with even 2" of lift on the late models. Some people get it, some people don't. I've seen it with a simple 1" shackle lift before.

 

[ehall]

If you have significant play and can hear the tail moving around, then it sounds like the output bearing is shot. Its not hard to replace, just pull the housing off and its right there.

 

[old_man]

OK, let me ask a question....Does your driveshaft have a dual cardan setup or simply two ujoints, one on each end?

It makes a difference on how you set up the angles.

 

[lazyxj]

After installing the lift I used an angle finder to check the angles on the transfer case output and the rear pinion.
I found they were just over 1* out from each other so I installed 1* shims to bring them back even, now the angles sit within .3* of each other. Should I not have done this? QUOTE]

With a 2-1/2" lift, a 3/4"-1" transfer case drop is about right to get the rear angles close to equal.

If the front shaft's pinion angle is not aligned correctly, it will contribute to the destruction of the transfer case's bearings and the u-joints.
This angle will change with lifts and after a transfer case drop is installed. As the rear of the transfer case is dropped, the front output shaft tilts upward.

The front driveshaft is a CV shaft and needs the angle set differently than the non-SYE rear.
On the front, the pinion angle (at the axle) needs to be between 1/2 and 1 degree (from FSM), pointed almost straight at the axle.
The slight misalignment is to keep the u-joint's roller bearing moving and lubricated.
Greater angles will start to develop vibs, increasing with speed and/or lower axle ratios.
With a stock suspension, the pinion angle is set with shims, on the LCAs.

If you are lucky, only the transfer case's front output shaft bearing is bad and not the rear needle bearing.
The rear bearing can be difficult to extract without the right puller.

 

[planewrench]

A simple question certainly did get muddied! You stated that you have a slip yoke in your fifth paragraph. In this case you have a bronze bushing in the tailshaft housing and no slip yoke eliminator. Sounds like the bushing is badly worn, perhaps partly because of vibes from the bad u joint. The bushing is available as a separate item and can be replaced, along with the seal. And in your case (no double cardan joint in the driveshaft) you want the tailshaft and the pinion in the same plane, i.e.= parallel.
The angles of the front driveshaft may need to be addressed as well, particularly if your jeep still has the low pinion D30. There was good info on that in one of the responses. Front can be a compromise of driveline angles and sufficient caster. Best way to narrow the vibes down would be to remove the front driveshaft for now.

 

[kootenayXJ]

A simple question certainly did get muddied! You stated that you have a slip yoke in your fifth paragraph. In this case you have a bronze bushing in the tailshaft housing and no slip yoke eliminator. Sounds like the bushing is badly worn, perhaps partly because of vibes from the bad u joint. The bushing is available as a separate item and can be replaced, along with the seal. And in your case (no double cardan joint in the driveshaft) you want the tailshaft and the pinion in the same plane, i.e.= parallel.
The angles of the front driveshaft may need to be addressed as well, particularly if your jeep still has the low pinion D30. There was good info on that in one of the responses. Front can be a compromise of driveline angles and sufficient caster. Best way to narrow the vibes down would be to remove the front driveshaft for now.

Much thanks for the clear reply. So there is no bearing in the rear output tailhousing on my NP231, just a bronze bushing? This clarifies things immensely for me as I've searched extensively and come across posts talking about a rear bushing, but also, a rear bearing. If nothing more than a new bronze bushing and seal I'd be a happy camper.

Yes, I still have the stock driveshaft, not a double-cardan type. There are two u-joints on the driveshaft and a slip-yoke from the tailshaft.

The rear driveline angles between the pinion and rear output on the transfer case were adjusted after the lift and are within 0.2-0.3 degrees of parallel. I assumed this was "close enough" since this was about as accurate a reading as I could get with my angle finder.

I did not touch the front caster or pinion angle, and yes I still have the stock low-pinion D30. I drove for a few days with only the front lift installed and experienced zero driveline vibes from the front end so I'd like to think it's close enough to stock at 2.5" to not upset the front end. Further checking with the angle finder is necessary I guess.

 

[planewrench]

Glad to help. I suppose some of the confusion arises from the fact that there IS a ball bearing in a slip yoke eliminator housing.
If you decide to replace the bushing, in my experience the best way to remove the old one is to slit it lengthwise with a hacksaw, being careful not to damage the housing.
Having said all that, if that doesn't help with the vibration issue (along with the new u joint), you just might need an SYE.
I just checked- Quadratec has the bushing.

 

[kootenayXJ]

Glad to help. I suppose some of the confusion arises from the fact that there IS a ball bearing in a slip yoke eliminator housing.
If you decide to replace the bushing, in my experience the best way to remove the old one is to slit it lengthwise with a hacksaw, being careful not to damage the housing.
Having said all that, if that doesn't help with the vibration issue (along with the new u joint), you just might need an SYE.
I just checked- Quadratec has the bushing.

I'm going to pull the driveshaft tomorrow and see what's up. Is there any way I can remove the tailhousing, install the new bushing and seal then re-install tailhousing + driveshaft without splitting the case? While I have the tailhousing off, is there any way to inspect and check the Mainshaft Rear Bearing?
I've attached an exploded diagram I found of an NP231 online, part # 30 is what I'm worried may also be fried and I'd like to check this before proceeding, hopefully without splitting the case.

Thanks for everyones ongoing patience. I know this is all basic stuff and I have been searching to try to educate myself as best as possible but of course I still have some questions.

 

[ehall]

The bearing is #30, it is at the end of the output housing #35, just before the tailcone #36

If you have slop, bearing is probably bad. The slip yoke is interference fit on the shaft.

 

[planewrench]

^ Never trust the internet! The "bearing" ( bushing) is # 37. This is what you need. The seal is #38. You will need that also. The tailhousing is #36. It is held on with three bolts around the perimeter of the base. Comes right off- reseal with rtv when you reassemble. And the slip yoke is NOT an interference fit on the shaft, ...... it slips, hence the name.

 

[kootenayXJ]

Thanks, that's what I figured from looking at the diagram but wanted to make sure I wasn't getting myself into more trouble.

I'm a bit concerned that bearing #30 will be shot, as ehall pointed out, but step one will be to pull the tailhousing and see whats up from there.

On a sidenote I actually found a rear output seal in my spare parts bin...but it's for a 242. I must have packratted that around for at least 7 years since I sold my 1990.

 

[kootenayXJ]

one last question, I promise.

My XJ was lucky enough to come with a harmonic balancer at the rear of the output shaft. Before I start tearing things apart I assume I'll need a gear puller to remove this in order to replace the bushing and seal.

I had a look in my FSM but didnt find any mention of the harmonic balancer and searching has only led to know that some jeeps came with them, others with only an oil slinger.

 

[planewrench]

Can you take a picture?

 

[Devilfrog]

Ok, just to muddy things up a wee bit more ... You have a 2000 XJ. Therefore you Do NOT have a tailcone retained with three bolts. You have a seal at that point and the out put shaft ride external to the transfer case. The slip end of the stock driveshaft slip onto the shaft and a rubber boot is crimped on both the dust shield and yoke ends.
I haven't seen the balance types before but the TJ's used them so search a TJ thread for removal advice.
Worst case ... Smack it off, the lower tail housing and mainshaft are both replaced during a typical SYE (unless doing the Hack 'n Tap manner, not really ideal on an external shaft 231 though).

 

[kootenayXJ]

just to follow up, pulled the driveshaft, inspected the case for damage. Everything *seems* fine. With the rear DS removed I don't feel any play in the output shaft, no funny noises when driven with the rear shaft disconnected in 4hi (essentially front wheel drive).

Turns out the small lift pulled the slip yoke too far off the splines, causing the yoke to eventually wear and start vibrating around. The splines on the output shaft *appear* fine but without a micrometer I can't tell for sure.

So now I'm looking at a HnT since I dont feel like splitting the case to do the install. Hoping I don't regret that decision..

I would be pretty happy to just have a driveable jeep at this point...If I had known a tiny lift like this would have caused me so much grief, I woulda just left it bone stock.