Vibrations in 4WD

[Tangerined]

Hi all, just looking to get some help with this issue. I have a 1998 with 4.0 and AX15.

I get what I assume to be drive line vibrations when I switch to 4 High. The vibrations get more intense with speed and isn't related to engine RPM. The weird part is that the vibrations continue even after I switch back to 2WD until I come to a complete stop, then the vibrations are gone until I switch back to 4wd again.

Bit of background, I had the Jeep completely apart to replace frame and tub due to rust, started in 2018 and just got it back on the road this Feb. In the process, I swapped over a Dana 30 and Dana 35 axle from a 4 cylinder TJ with 4.10 gears. Installed a 2" lift, 1" body lift, 1"MML. Rebuilt the driveshafts with Spicer U-joints, also replaced the centering ball in the double cardan joint in the front drive shaft.

My first thought was that I unbalanced the front shaft when I rebuilt it but wouldn't I get the vibrations all the time since the front shaft is always turning? Or something wrong with the front diff? Or something wrong with the transfer case?

 

[Evan77]

I will let more experienced users try to answer this question such as @Jerry Bransford but since it's an issue that only happens in 4wd that could possibly point to a problem with your tc.

 

[jeepguy03]

1. If you switch back to 2WD but the vibrations continue until you come to a complete stop, your 4 wheel drive might not be engaging completely until you stop.

2. Considering #1 is true, that means the issue is only present when the front axle is engaged. I would remove the front shaft and drive around the neighborhood without it to see if the vibrations are still present.

 

[CharlesHS]

I agree.... suggestion #2 would be your first step to localize the source of the vibrations. IF this doesn't isolate the source; then reinstall the front ds and remove the rear ds.

 

[Tangerined]

Ok sounds good, I'll try and pull front driveshaft tonight and will report back.

 

[Tangerined]

Ok just popped the front driveshaft off and took it for a spin. There are no vibrations in 4 Hi.

 

[Tangerined]

So it's the driveshaft then? I should take it to get balanced?

 

[jeepguy03]

How do the joints feel in the driveshaft, is there any binding?

 

[Tangerined]

How do the joints feel in the driveshaft, is there any binding?

Joints feel okay, everything rotates freely.

I also forgot to mention that it only seems to do this under load. I had the Jeep up on jack stands and ran it up and down in speed in 4WD and there weren't any vibrations.

 

[Tangerined]

Still chasing this issue. I just noticed that when I take it out of 4WD but the vibrations are present, I go and do a tight turn, my tires are binding like I'm still in 4WD. This would mean the issue is in my transfer case right? What could it be? Would a rebuild with replacing all the bearings fix it?

 

[01TJ-Blues]

check pinion and transfer case bearings for play. Also make sure that the driveshaft is aligned. Aligned as in that if someone slipped the two halves apart then out it back together not aligned in how it was balanced. The yokes should be 90 degrees from one end to the other I believe. If not then the same position but you have only 4 ways it could go and be correct. You’ll know immediately when it’s right....or wrong.

 

[Rubicon88]

You can't just flip flop a u joint and say, yep...it's good. (Back and forth..not swapping)
You have two u joints in your front axles as well.

While all these things are turning in 2wd, none have applied engine torque. Just rolling resistance is the load and that is nothing ultimately.

You've said this makes no vibrations with the driveshaft removed in 4wd.

Ok....but....that only means your TC is probably ok. Once you removed the front driveshaft you also removed the front torque from the engine to the front axle. (No driveshaft)

I'd say you absolutely positively should focus first on your u joints in the front driveshaft...and the driveshaft spline positions...
And your u-joints in the front axles.

Putting it in the air won't show much as there isn't even any rolling resistance. It's just air.

Lastly...your 4wd is staying engaged until it essentially becomes unbound. It stays bound up until you stop and reverse or get some lateral leverage.
No big deal there whatsoever.

Good luck.

 

[Tangerined]

I just replaced my front pinion seal, replaced the crush sleeve since I don't think I got it to crush the first time. This time I started it on a press and torqued until I got 9 inch/lb on the preload. I was thinking this could be the cause of the vibrations but it didn't fix it.

The front axle u-joints are good and turns smoothly, I replaced the right one with a brand new spicer 5-760x, left one was smooth so I left it alone.

I did turn the 1 half of the driveshaft 90 degrees hoping it would fix it but it hasn't. Perhaps I'll take it to the local drive train shop and have them balance it.

The other thing I noticed was that there's also a mechanical whirring/whining sound along with the vibrations when I shift to 4wd. It begins as soon as I shift to 4wd when I still have the clutch pedal pressed down.

Also, it seems like there's a leak at the front output of the TC now, that wasn't there before. Not sure if that's a result of the vibrations or a symptom.

Thanks for the help guys.

 

[freedom_in_4low]

1. If you switch back to 2WD but the vibrations continue until you come to a complete stop, your 4 wheel drive might not be engaging completely until you stop.

2. Considering #1 is true, that means the issue is only present when the front axle is engaged. I would remove the front shaft and drive around the neighborhood without it to see if the vibrations are still present.

Lastly...your 4wd is staying engaged until it essentially becomes unbound. It stays bound up until you stop and reverse or get some lateral leverage.
No big deal there whatsoever.

Not to derail the thread, but I was having trouble picturing how this could happen until I pulled up the photos from doing my SYE. Unlike the range selector fork which rides in a groove on the sector plate (and is therefore pushed and pulled into and out of low range), the mode fork is pushed into 4wd by the plate but depends on the spring to push it back out of engaging the chain sprocket once you've shifted the lever into 2wd. I can totally see that hub hanging up when under load or bind.

 

[Rubicon88]

I just replaced my front pinion seal, replaced the crush sleeve since I don't think I got it to crush the first time. This time I started it on a press and torqued until I got 9 inch/lb on the preload. I was thinking this could be the cause of the vibrations but it didn't fix it.

The front axle u-joints are good and turns smoothly, I replaced the right one with a brand new spicer 5-760x, left one was smooth so I left it alone.

I did turn the 1 half of the driveshaft 90 degrees hoping it would fix it but it hasn't. Perhaps I'll take it to the local drive train shop and have them balance it.

The other thing I noticed was that there's also a mechanical whirring/whining sound along with the vibrations when I shift to 4wd. It begins as soon as I shift to 4wd when I still have the clutch pedal pressed down.

Also, it seems like there's a leak at the front output of the TC now, that wasn't there before. Not sure if that's a result of the vibrations or a symptom.

Thanks for the help guys.

Huh?
You aren't moving and with clutch in and you pull up on the lever to engage the 4wd you hear a noise?

 

[Tangerined]

Huh?
You aren't moving and with clutch in and you pull up on the lever to engage the 4wd you hear a noise?

Oh no sorry, I meant that when I shift into 4wd while moving. Not sure if that makes a difference since it's technically in neutral with no engine load on it.

 

[Tangerined]

Update on this incase anyone else runs into a similar issue.

I finally took the front driveshaft to a driveline shop and had them balance it. Shop said the end facing the transfer case was quite a bit out of balance. Now there are no more vibrations in 4WD now.

Strange for me to think that an out of balance driveshaft only causes vibration when underload but it was actually the case.