Help me figure this one out

Ron said:
Let's work backwards.
The only time its gone is with no shafts. Since it follows both or either shafts that leads me to only 2 possible solutions

1) Both drive shafts are out of balance. Since it's you I am doubting this is the culprit just acknowledging it is feasible - We've checked the balance on both shafts, both balance near perfect, the rear has .001 run out. I'm confident it's not the shafts, since it does with just the rear installed and again with with just the front installed.

2) The issue is related to loading on the drivetrain. With no load no vibe. - Correct
So now let's dive into #2
A) Its present regardless of T-Case selection so lets eliminate that as the culprit. - Correct

B) Rebuilt Trans which eliminates internal trans issue, still leaves potential for some external alignment, mount hole wallow, bind issue however unlikely it may be still a possibility.. - Understood

C) Engine issue

If it were me and it couldnt be lived with (BTW have we established in this thread what kind of vibe we are talking about? Are we talking .."There is a slight vibration there can you feel it?" or are we talking "Holy Shit any worse and this qualifies as death wobble") but my first action would be to swap every mount in the vehicle. Both motor mounts, trans mount and t-case mount. The mounts primary purpose other than locating and maintaining location is to isolate rotational harmonics from the cabin. A failure in any of these could transmit those vibes even if they dont show any visible signs of wear.

The Vib is not death wobble intense, nor your "ok this is a jeep and somethings gonna vibrate" but enough that if not if not taken care of, will make what ever is making the vib cause a catastrophic failure imo. I should add to, the vib is making the bearings in both the t-case and rear extremely warm after only a few miles of driving.

If those are replaced and the vibe remains the only remaining culprit is the engine.
Id check the harmonic balancer and the crank shaft end play. And not visually, Id get caliper level run out measurements

Seems to me if the balancer was bad, you could make it vib with just revving the motor? Noteworthy of checking though.


EDIT - Wait just saw your response on the Clutch....before I did any of the above Id have the clutch and bearing replaced and the plate checked for run out/warpage on machine and re balanced. Visual isnt going to identify this level of vibe that I am assuming we are talking about.

Agreed.


Double Edit - Have alternate tires, wheels been used on any tests?
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I haven't changed the wheels and tires out, but I have run the rear on jack stands with out the wheels/tires and it has the same vibs.
 
I'm wanting to say bent axle-tube so bad (it is a jeep after all). But you said that it does it with only the front shaft installed, and also with only the rear shaft installed. You definitely have gotten yourself into a mess.
 
So it does it in 3rd gear high range, and 5th gear low range. Are those both close to the same vehicle speed?
 
drkelly said:
So it does it in 3rd gear high range, and 5th gear low range. Are those both close to the same vehicle speed?
Click to expand...

IIRC, yes, roughly 35mph.
 
Oliver's said:
I haven't changed the wheels and tires out, but I have run the rear on jack stands with out the wheels/tires and it has the same vibs.
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Were the shafts checked and swapped with it on stands? or was that done on the road? If the wibe is from the axles it would happen on the road independent of the driveshaft. If it was on stands it would only be one that was loaded.

You swapped out the tcase, but was it a known good one?

At this point I would guess that its something in the planetary/chain in the case.
 
check the leaf spring centering pin. had one shear on a bronco that cause the axle to slide back and forth at certain speeds. obviously, when the axle shifted i got a vibration.
 
Bent axle tube or axle shaft?
 
We replaced the rear wheel bearing just to do it and one Axle shaft that had some pitting on the bearing surface. No change.

The customer has it back now, so unfortunately this one may go unsolved.
 
Oliver's said:
but I have run the rear on jack stands with out the wheels/tires and it has the same vibs.
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This is a big indication that it's in the rear axle/wheels/tires because of the following reasons:

  1. Driving down the road with only the front shaft induces the vibes - This eliminates rear drive shaft
  2. Front drive shaft removed induces vibes - This eliminates front drive shaft
  3. 2 different transfer cases and 3 different SYE's were used - likelihood of both cases and all output shafts being bad is very small
  4. Running the rear while on jack stands induces vibes - this eliminates the front axle/wheels/tires entirely as they aren't spinning and also indicates that no load on the tires is needed.
  5. The vibration occurs whether in 2wd or 4lo - This eliminates the trans as the output of the trans is rotating at different speeds to obtain the same vibration around 35mph
 
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adamk said:
This is a big indication that it's in the rear axle/wheels/tires because of the following reasons:

  1. Driving down the road with only the front shaft induces the vibes - This eliminates rear drive shaft
  2. Front drive shaft removed induces vibes - This eliminates front drive shaft
  3. 2 different transfer cases and 3 different SYE's were used - likelihood of both cases and all output shafts being bad is very small
  4. Running the rear while on jack stands induces vibes - this eliminates the front axle/wheels/tires entirely as they aren't spinning and also indicates that no load on the tires is needed.
  5. The vibration occurs whether in 2wd or 4lo - This eliminates the trans as the output of the trans is rotating at different speeds to obtain the same vibration around 35mph
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If you read pack through all the way. He also did it on a lift with just the front shaft installed.
 
The jeep ended up back here again. The customer took it to another shop for another diagnosis. The shop said they found a spot on the ring gear that had zero back lash. I had the owner bring it back for me to check. After literally checking each tooth on the ring gear I only found a various of .001. I then took the ring off the true trac and ran it in the lathe. Zero run out on the flange and .005 on the journal. ECGS verified that wasn't enough for any concern. I reinstalled the ring gear 180 for what it was just in case, same pattern as before.

I moved on to the axle shafts to check for run out. The Pass side shaft had .005 at the bearing and at the spline, but had .025 in the middle. Thinking I was on to something I pulled the driver side (brand new) back out and checked it. To my surprise, it had almost the identical amount of run out.

I put both shafts back in and installed the c-clips, put the brake drums back on, and the wheels. I grab the tire once the lugs are back on and felt and odd lateral movement, not in and out c-clip related movement, (think old school front wheel bearing check). I grab it again to check myself and sure enough both sides do it, pass. side slightly worse. I put my mag base indicator on it, Pass side moves .017 and the Driver side .012. Is this normal? I honestly can't recall feeling that kind of movement on a rear axle shaft before.

If this is not normal, what could cause this? Bent housing? It has brand new wheel bearings, so I rule that out.

Thoughts?
 
Oliver's said:
The jeep ended up back here again. The customer took it to another shop for another diagnosis. The shop said they found a spot on the ring gear that had zero back lash. I had the owner bring it back for me to check. After literally checking each tooth on the ring gear I only found a various of .001. I then took the ring off the true trac and ran it in the lathe. Zero run out on the flange and .005 on the journal. ECGS verified that wasn't enough for any concern. I reinstalled the ring gear 180 for what it was just in case, same pattern as before.

I moved on to the axle shafts to check for run out. The Pass side shaft had .005 at the bearing and at the spline, but had .025 in the middle. Thinking I was on to something I pulled the driver side (brand new) back out and checked it. To my surprise, it had almost the identical amount of run out.

I put both shafts back in and installed the c-clips, put the brake drums back on, and the wheels. I grab the tire once the lugs are back on and felt and odd lateral movement, not in and out c-clip related movement, (think old school front wheel bearing check). I grab it again to check myself and sure enough both sides do it, pass. side slightly worse. I put my mag base indicator on it, Pass side moves .017 and the Driver side .012. Is this normal? I honestly can't recall feeling that kind of movement on a rear axle shaft before.

If this is not normal, what could cause this? Bent housing? It has brand new wheel bearings, so I rule that out.

Thoughts?
Click to expand...

what are the quality of the wheel bearings? shaft tolerances plus bearing tolerances... = poop? just happened to be the odd pairing of two max tolerances?

(not enough coffee, too much beer - spitballin :) )
 
Parts store bearings, Nationals IIRC.
 
I just calipered a set of National bearings going into a '68 C10 (12 bolt) we are working on. New shafts measure 1.615 at bearing surface, new National bearings measure 1.616 from roller to roller (pushing pretty hard out on the calipers). But FYI the ID of that bearing, per National is listed as 1.622. Not sure why the bearing ID is listed as .006 over what it actually calipers (probably not the most accurate way to measure it), but that seams like .006 would make it a bit sloppy. I have no noticeable play in the bearing on the shaft.

Not sure if this helps at all, but we are going through our own issue on this truck and figured I would give what I could.
 
Pull both shafts and run it in 3rd. I am not too very familiar without looking at a diagram but you said it vibes with front shaft only, rear shaft only, and on stands. Swapped case, no change. Definitely not in rear gears. My money is on the trans..... Before gear swap, it was high 3rd and 4th. After gear swap it was still 3rd. Worth a shot but it won't be loaded like with a shaft in, keep in mind... I have a good yj axle pair if you can get them down there, but I bet it's in the trans.. idk how but that's the only thing that hasn't been tested or changed.
 
Pull both shafts and run it in 3rd. I am not too very familiar without looking at a diagram but you said it vibes with front shaft only, rear shaft only, and on stands. Swapped case, no change. Definitely not in front/rear gears or the TC. My money is on the trans..... Before gear swap, it was high 3rd and 4th. After gear swap it was still 3rd. Worth a shot but it won't be loaded like with a shaft in, keep in mind... I have a good yj axle pair if you can get them down there, but I bet it's in the trans.. idk how but that's the only thing that hasn't been tested or changed.
 
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