diesel402004

Hey all,
Hope everyone is having a good winter (what there is of it). Been trying to troubleshoot a strange driveline noise on cold mornings and an increasing driveline shudder over the past year. To start:

1. On cold mornings there is a noise while moving slow (first gear) coming from the cab hump area (transfer case shifter area maybe?). It makes a noise like a spun bearing and only does it for the first .5 mile or so. No more obvious noise after that. Transfer case gear oil is fresh and up to level and had no obvious metal when changed last year. A518 tranny fluid is normal and up to level with no obvious metal/or burning.

2. A mild shudder has been getting more noticeable when accelerating in first. Not noticeable at all in other gears.

Both symptoms can be avoided if I have hubs locked in in 4WD. Meaning the front driveline takes stress off of failing area maybe? It seems to indicate less of a tranny issue because the shudder would still be there?

My suspicions/ideas are as follows:
1. Torque converter (although it should still do it in 4WD).
2. Failing tranny somehow? Maybe OD bushing has spun and makes noise until fluid hits it (does that bushing/bearing spin while in first?), or shudder is a separate issue from a solenoid or something
2. Spun bearing in transfer case that only makes noise until gear lube hits it. This in turn is allowing more internal slop to exist and is showing up as a shudder in first (this possibility seams to be bolstered by a long-time feeling of resistance year-round when first starting off)

Has anyone experienced this with the A518 and NP205? All other driveline possibilities have been eliminated: U-Joints, Rear Diff, Carrier bearing, loose yoke nuts etc. Want to dive into it without spending too much time on the wrong issue. Both Tranny and transfer work fine otherwise and are original.

Let the ideas begin! Thanks in advance.

thrashingcows

Have you replaced the front axle shafts U-joints?

j_martin

Do you feel any vibration in the shift lever. The OD unit has a radial bearing in it that's doing a thousand pounds or so of thrust service. When it fails, it makes wierd noises, then fuddles the whole transmission with shrapnel. (don't ask)

Same unit has OD and straight clutches in it. Straight clutch might be slipping. If the OD solenoid were leaky, it might make it slip till the fluid warmed up. Should be some carnage in the clutch if that's happening.

Spring tension holds it in straight, till overcome by the OD clutch. Same piston releases straight and engages OD.

I'd pull the pan and look for debris.

KRB

Can you "feel" the noise when holding the transfer case lever?

You wouldn't by chance live in Fulton Co would you?

cougar

If both symptoms go away with the hubs locked, I'd say you have a lack of lubrication problem in the transfer case. One of the many reasons I never unlock my hubs.

mknittle

I had a bad valve /valve body. do something like that. A real PITA to diagnose.

j_martin

I had that happen after the complete rebuild when the tail shaft bearing spalled. Had a whine, and I could feel it in the shift lever a bit. Transmission shop tore down the rear end. It needed clutches and a couple of hard parts. Some of the noise went away, but I could still feel it. Pulled a double about 3500 miles on vacation back and forth through the Rockies several times. Took it back and told them to pull the pan and find the noise. The front 2 screws for the valve body were laying in the pan.

They said they've seen it before in these 518's if they're behind a Cummins.

All I have to say is it's one tough transmission to do that with no damage they could find.

diesel402004

Thrashing:
Front shaft fine especially as it does it only when NOT in 4WD

J_Martin, KRB:
I like where you're going: I only noticed the usual vibration, but I will grab it when acceleration and see if it matches the squalling, shudder I can hear. The normal for the last 100K has been a slight whine when in OD. The valve body or output shaft bearing of the tranny has been a thought, but hard to diag. before total failure. The pan has shown nothing unusual in the last 3 flushes (every 10K). Has anyone else had a bearing failure in the transfer from lack of lub.

93-12Smoke

Check you exhaust mounts. I broke one and my pipe was hitting and rubbing the u joints at the case.

93-331-29psi

I'd grab a pry bar and check the rear shaft joints. I had a similar issue with my front u-joint and it was only at low speed. Joint had very minute play in it, replaced both and everything purrs.

diesel402004

Howdy again all. Bringing this back for fresh looksy. So....Ignoring the shudder in the back, I'm trying to narrow down the spun bearing like noise under the passenger side hump when cold: it doesn't do it if I have the transfer in 4 (Lo or Hi). I don't have to have the hubs locked in. So, in a nutshell, it ONLY does it when cold, moving slow and in 2HI. I know the front shaft turns slightly when freewheeling so maybe the front output shaft bearing is spun and it only makes the noise when there isn't a load on it and it's spinning slowly while in freewheeling mode? Has anyone experienced this noise from their NP205?

KRB

I know you are concentrating on the hump noise and ignoring the rear shudder but do you have a limited slip rear end? If so, that could be your shudder. Mine will do that under a heavy load or acceleration. I put new lube in and additive but still get it so I guess my clutches are worn, maybe your issue too?

diesel402004

Hey KRB,
Great thought, but I had clutch pak replaced early on (by someone else), and I did confirm the old one was worn. Supposedly there was no wear on the worm gear. Going to pull the diff this summer and verify it's as good as they indicated because it didn't fix the issue at all. Tried adding more modifier and that didn't help either. Good news is I can pretty much ignore it (like this past 1K road trip) and convince myself it's not really that bad. Just a pita as I KNOW it wasn't there this time last year.

D

diesel402004

Reviving this thread again! Got my tranny rebuilt (OD was whining and metal in pan told me it was time). Now that I have THAT out of the way, I still have the intermittent sound coming from front of hump when first starting out in first few miles. I've put truck in air and tried getting the noise to come out (of course I can't replicate it when I want) I've put it in and out of 4WD and sped up and down just like on the road and cannot get the noise to appear. Also, repacked front hubs to be sure. Has anyone noticed their front spindle bearings showing wear? The noise only appears when I'm in 2Hi without the bubs locked. As soon as I hear the noise I can stop and shift to 4HI (don't even need to lock hubs) and it doesn't reappear. If I leave the transfer in 4HI (no hubs locked) while first starting out in morning the sound never appears. This thing is driving me crazy because it's definitely getting louder and more consistent (except when I have it in the air and WANT to hear it)

KRB

This almost has to narrow it down to the transfer case.

When you ask about worn spindles do you mean king pins?