Help Diagnose A Vibration And Sound After Sye ?

[skidoo_j]

Okay so yet again I fix one problem to discover a new, or maybe my fix has issues. 

 

What I did: 

97 NP231 rebuilt with 6 planetary (correct gear cut for year), 1 1/4" chain,  completely new bearings and seals through out and installed a tera 2low.   

 

I got a driveline from tom woods with standard ends (no double cardon)

 

 

My new symptom:

When driving at 55-65 there is a very deep growl that is continuous while driving at this speed.   However if I press the clutch in or pop it out of gear it's not there.    

 

I've driven it up to 75 then taken it out of gear and coasted through that range and nothing.  

 

It only occurs while under power.  I can even make it go away by taking my foot off the gas pedal.   It will happen in 3rd, 4th, and 5th as long as I'm near that speed range.   

 

 

My thoughts are:

I messed up during the rebuild

Driveline U joint possibly bad?

Ring / pinion or pinion bearing?

 

 

I did check fluid on the diff the week before the transfer case exchange (currently less than a tank of gas on the new transfercase.) 

 

 

My current plan is to remove the rear driveline and run in 4x4 and see if the growl is still there at that speed but am concerned running if fwd with no slip may have some adverse effects, but  I need to start somewhere

 

another option but not one I want to do is to put the old transfercase and driveline back in and see if the noise / vibration is there.  

any other suggestions or knowledge would be appreciated.   

[skidoo_j]

No leaks from transfer-case and fluid is full. 

 

Need to resolve it asap while its still under warranty.  

 

I have trouble with it being drive line vibrations as i was running at almost 12*  and with the sye i'm about 6-7* pinion to line angle.  I'll have to go out and measure all angles again to make sure that with the sye i don't' need to remove the transfer case shims.  although maybe with it having fixed ends now, maybe the play in the slip yoke absorbed the vibes in the original shaft?  

 

Although I have noticed in the little bit of driving with this combo my axle wrap or whipping is almost completely gone.  The bed of the truck appears to be actually staying settled.   

[skidoo_j]

Called Tom Woods.  They think it's pinion transfercase angle relationship and the reason I didn't notice it before is because the slip yoke was so loose that it absorbed the vibes.   So they suggested rather than removing the rear if I can check the pnion angle vs trans angle to shaft.   Wanting me to ensure they're parallel,  or the pinion is pointing 1 degree to the ground more.   

 

 

This is really going to suck if i have to shim the damn axle.  The reason I went with the single cardon axle to begin with so so I didnt have to shim the rear axle, so If it gets damaged, vehicle wrecked or if I sold it I could swap the old stuff back in and it still be drive able.      Trying to be frugal seems to always bite me in the @$$ when it comes to these jeeps.  

[skidoo_j]

I went out and measured my angles and I'm pretty damn close to parallel.   The pinion is about  1/2* up rather then down, so I'll try and remove the shim under the trans mount.  I'm thinking this will bring the yoke at transfer down and they may end up perfect.   It's the fastest trial.   Will post results.   

 

 

 

 

Does anyone know what this jargon from my tom woods invoice references?   BEG@46.875" T-C

 

That number was on the tag attached to the drive shaft when I received it.  The reason I'm curious is that is not my resting length nor any of the measurements I provided them.  I neglected to ask during my phone call with them.

[Oddmodman]

When you replaced your driveshaft did you put in a new U-joint or check if the old one was good? I know it's low-tech but it's the only idea I have.

[skidoo_j]

When you replaced your driveshaft did you put in a new U-joint or check if the old one was good? I know it's low-tech but it's the only idea I have.

It came with two new "gold" u-joints.  

 

 

 

 

 

Well removing the shim did not eliminate the vibration, so not knowing if it's my desire for that to be the fix or not I will remove the rear shaft after dinner and go for another test drive.  I really do hope I didn't mess up the transfercase build.  

[HOrnbrod]

I too replaced my drive shaft with a Tom Woods unit because my original could not be balanced. After I did my lift I had a vibration that started at about 35MPH and ended at 55MPH while accelerating. The new shaft had the same 1310 u-joints you got. Since the shaft was new along with my lift and regear, I went through everything else first: tranny drop, axle shims, rechecked the gears, etc. Nothing helped, so I finally replaced the u-joints with Dana 1310 greasables. They were the problem for me - instantly the vibes were gone. Just relaying my experience - I have no idea if your vibes are being caused for the same reason. Sounds similar though.....

[skidoo_j]

Thanks for the advice hornbrod.

 

 

 

Well they say you learn something new every day.     

 

 

DO NOT EVER DRIVE IN FRONT WHEEL DRIVE WITH AN AUTO LOCKER ON THE ROAD!!!!!

 

 

I just about killed myself and an oncoming car.   I was going about 55-60 and the locker decided to disconnect, this caused me to serve into oncoming traffic.  Then all the sudden it relocked jerking me back over thus making my correction a major over correction.   The dogs got thrown to the floor but first hitting the door panel then dash.   After I checked my pants I decided to drive back home with the CAD disconnected.   And the same thing happened, but when I took my foot off the accelerator only the drivers front wheel slowed jerking me back into the wrong lane. 

 

 

It was a very wild test drive, but I did eliminate the transfercase as being the culprit.  So now its either drive line or the diff.   My angles to driveline are 7.5* at transfer  and about 6.8* at pinion, so the angles should not be causing vibes due to phasing.   I can't imagine 8* would cause vibes.   I can hear the ring and pinion in the rear now, not sure if it was always there and just hyper sensitive. 

 

 

I'll put the rear shaft back in, and grease everything on it really good.  and run it for a week or so while I finish up my zj brake conversion parts.  I'll open the pumpkin when i convert and check the gears prior to installing the truetrac.