Transmission sound goes away in neutral (1 Viewer)

[bmorgan]

I promise I've read all I can and I'm getting mixed results.

Speed related sound - goes away in neutral at speed.

I have several fzj80s. My wife's is a 97 with about 220k. It started a vibration noise that is speed related - sounded like running over a rumble strip but very low and mild. I know the birfield soup is there and I need to do a front end job. I already bought everything to do the job (marlin seals), but then she tells me it's getting worse and she's concerned with speeds over 45. So I drive it. It's changed a lot in a few weeks. It used to be like driving over a rumble strip but now it's loud and the truck sounds like it's winded. The vibration seems to go away when I drop the transmission into neutral at speed. The fluid appears to be in good shape - it's certainly not low and I don't think it smells burnt. Before I take it to a shop, does anyone have any advice? I wanted to do the front end job before I took it in - just to rule it out, but I'm concerned I'm running out of time - AND I broke my collarbone, so I don't know if I can for another few weeks. I really appreciate any advice.

The torque converter went out in mine years ago. The symptoms are very different. Thank you in advance!

 

[ajax1]

Sure not broken exhaust hanger or mount? I’d leave the marlin seals for the mini truck guys and run oem seals up front. Known issues with those seals on fulltime trucks

 

[Rifleman]

Sure not broken exhaust hanger or mount? I’d leave the marlin seals for the mini truck guys and run oem seals up front. Known issues with those seals on fulltime trucks

As Ajax1 said above, you'd be smart to go with the factory OEM inner axle seals. That is unless you REALLY enjoy taking your steering knuckles apart. The Martin seals have been known to leak after only a few months of use.

 

[BILT4ME]

Sounds to me like u-joints.

 

[bigredmachine]

could be a number of things, first I would check the u-joints. if the u-joints feel good you can lock the cdl and frive with the front shaft out and then with the rear drive shaft out to check for the vibration.

does the vibration start at a certain speed and can you make it go away by driving with the od off? if so that could be the torque converter

 

[bmorgan]

I appreciate the comments on he inner seals. The reason I'm using those is I had a problem with using oem in Buiser (my LC). I just haven't had luck with the OEM seals. The Marlins fixed mine, so I thought I'd use them again. But that's not the focus of this post (but still appreciated and I'll reconsider).

I REALLY hope it's the ujoints. BUT, wouldn't a ujoint problem NOT go away with shifting into neutral? I'm traveling for work today, so I can't do any testing until tomorrow evening. The vibration seems to be pretty consistent with speed (IE - there appears to be no specific speed where it starts.) I have some ujoints on the shelf, so I could pull the shafts and change out the joints at the same time. Probably needs it anyway. Thoughts?

 

[bigredmachine]

BUT, wouldn't a ujoint problem NOT go away with shifting into neutral?

not necessarly, going into neutral is taking a load off of the drivetrain and it sounds like your only getting noise/vibes under load.

see if the vibes go away with the truck out of od

 

[cjmoon]

I second u-joint taking the load off of it in N makes it happy enough not to vibrate. When stopped shifting back and forth between R and D do you get a clunk?

 

[ATXLX]

My vote is an exhaust hanger, mine are gone and I need to shift it into N at a stop light to shut it up, easy to check. Maybe take a mechanics stethoscope and just start poking around with a helper shifting it into D and N to try to pinpoint the source.

 

[bmorgan]

This truck actually has new exhaust hangers. But the truck runs smooth at a light. This is all speed related, not idle related. So I can't see how it can be exhaust. It's got to be driveline. I'm hoping it's ujoints. I'm out of town for work until tomorrow night. I think I'll hit them all with a shot of grease just to see if the noise changes. Does that sound reasonable?

 

[bigredmachine]

I think I'll hit them all with a shot of grease just to see if the noise changes. Does that sound reasonable?

at this point if the u-joints are toast the grease will make little to no difference in noise or vibration, still worth while to give the joints some love anyways

 

[Tools R Us]

at this point if the u-joints are toast the grease will make little to no difference in noise or vibration, still worth while to give the joints some love anyways

Generally if they are that wasted, it would be easy to see, feel. Block the tires so it cant roll, shift the transfer to neutral, so there is slack in the drive shafts, and check for play at the joints. In most cases, greasing them will make a difference, cheap, easy test. Often a rumble strip sound is dry spindle bushing(s), is the knuckle moly grease level correct, ~1/2-3/4 full?

 

[bmorgan]

ok - so this is my plan of attack: I know I have to rebuild the front end (replace the inner seals, etc.) I KNOW I should have replaced the bearings when I did it the first time, but I didn't. These could be the original bearings with 220k miles on them - not sure. I'm going to do that job. But before I do that, I'm going to give the ujoints a shot, one driveshaft at a time, see if that makes any difference. I'm still going to change out the bearings and redo the front end (they've been leaking for a while now so it's overdue) but if the ujoint shots make a difference, I'll do that job tomorrow once the front end is done.

I really appreciate everyone's input. I've been on mud 13 years now. This is such a great community. I'll post my findings.

 

[bmorgan]

Just checked - looks like the front most ujoint has some play in it. I'm going to go ahead and change that. I have a couple ujoints on the shelf. Sure does help having 3 of the same vehicle. Makes hording parts less ... "hordy".

 

[bmorgan]

Well, that was it. 100%. Runs great again. Thank you so much. I was a phone call away from taking it to the transmission shop. The front-most ujoint was very messed up. It even had pieces of the race missing - chunks gone. I don't know how that could have happened.

Just in case anyone stumbles upon this, here is the write-up for replacing the ujoints. how to replace the u-joints in your 80

 

[BILT4ME]

Well, that was it. 100%. Runs great again. Thank you so much. I was a phone call away from taking it to the transmission shop. The front-most ujoint was very messed up. It even had pieces of the race missing - chunks gone. I don't know how that could have happened.

Just in case anyone stumbles upon this, here is the write-up for replacing the ujoints. how to replace the u-joints in your 80

You're welcome!