Is this trans mount cooked?

[JLav211]

Hey all,

I've had a phantom vibration I've been chasing to no avail. Feels like dead-center of the truck, under my seat. We've tightened up the exhaust as much as possible but still hearing a very real vibration noise at highway speeds and upon deceleration. Thinking it might be a transmission mount, so wondered if any of you can tell based on the photo below if my mount is due for replacement. It is almost certainly original to the truck (250K miles) so perhaps should be done regardless but this noise is driving me nuts.

 

[Kernal]

What model are you working on (helps to put in your signature block)

What did you do to "tighten up" the exhaust system?

The exhaust system on the 95-97 FZJ80's has three square rubber hangers or isolators which tend to crack in half horizontally from age. When that happens the exhaust system will bounce and vibrate but not fall on the ground due to the interlocking design of the hanger brackets.

 

[Gerry McGerry]

Jack up the transfer case lightly and look for any cracks in the rubber mount.

 

[CharlieS]

When you jack it up also look for separation of the rubber from the metal. The one on my 300k mile rig was completely separated.

 

[mudgudgeon]

If the mount is not cracked a suggested, check uni joints.

Vibration on deceleration is a classic symptom of bad uni joints.

Pull front and rear drive shafts out of the vehicle to inspect uni joints.

 

[Broski]

The slip joint is also suspect check it closely.

 

[CruiserDave]

Grease all driveshaft joints and slip yolk if you haven't already. Then drive it around to get that slip yoke grease moving and see if it vibrates.

 

[JLav211]

What model are you working on (helps to put in your signature block)

What did you do to "tighten up" the exhaust system?

The exhaust system on the 95-97 FZJ80's has three square rubber hangers or isolators which tend to crack in half horizontally from age. When that happens the exhaust system will bounce and vibrate but not fall on the ground due to the interlocking design of the hanger brackets.

I have a 97 LX450. Will get my sig updated.

We added a hangar that was missing and replaced a rubber mount. We did not replace the other isolator blocks. I did notice the one off the side of the trans is very soft / flexible, so perhaps I need to look at those.

If the mount is not cracked a suggested, check uni joints.

Vibration on deceleration is a classic symptom of bad uni joints.

Pull front and rear drive shafts out of the vehicle to inspect uni joints.

Interesting. The noise is fairly steady on the interstate. However, if you're at highway speeds and, say, take your foot off the accelerator for an exit ramp, you'll hear it most noticeably from 65-50; I never hear it around town at 30-40 MPH. Probably all semantics but that's the experience thus far. Honestly, I've had the the thought that the driveshaft was suspect for a while, so maybe I should listen to my gut.

I found this thread which seems to describe a very, very similar scenario: 80 Series Aus forum

 

[Saito]

Your shifter might be doing a little dance. Mine was toast. Looked like yours. I could feel the drivetrain shift a tad on acceleration.

 

[Kernal]

"still hearing a very real vibration noise at highway speeds and upon deceleration"

At 4am my brain missed that sentence, more likely a moving/rotating component as mentioned above.

It's all been suggested above but FWIW, how often do you lube the U-joints and slip yolks?

Have you lubed those components since the symptoms started? Any change/improvement afterwards?

Have you checked the fluid level in the gear boxes (diffs and transfer)? Any leaks around the pinion seals?

Is your truck lifted and/or running aftermarket driveshafts??

 

[mudgudgeon]

Adding grease to driveshafts is a good diagnostic tool.
If you pump in fresh grease and the vibration disappears, time for new uni joints. Fresh grease will only give temporary relief with bad uni joints

 

[JLav211]

Guys, appreciate all the help. Upon seeing multiple people complain about a similar issue following the installation of a lift, I ordered the Tom Woods front driveshaft. I felt confident given the near identical descriptions of what I'm experiencing - along with the symptoms developing after I installed a 3-inch lift - that this is the source of my problem. Will report back once installed.

 

[IdahoDoug]

FYI, the news it happened at the same time you installed a 3 inch lift should have been in your first post. Kinda like asking why your engine is running hot for a week of suggestions, and at the very end mentioning it started the hour, minute and second you replaced the factory fan with an electric one.... Hope this is the issue for you.

 

[JLav211]

FYI, the news it happened at the same time you installed a 3 inch lift should have been in your first post. Kinda like asking why your engine is running hot for a week of suggestions, and at the very end mentioning it started the hour, minute and second you replaced the factory fan with an electric one.... Hope this is the issue for you.

Full disclosure, I moved out of state and left the truck 8 hours away for an engine rebuild. I didn't have the context of picking it up and driving it right away as the lift kit was installed probably 1.5 years ago, the engine was rebuilt afterwards, and then it took 2 months to get down to my new address. I didn't have that "context" of, "Oh, I just installed a lift and I have this noise," as truthfully, I didn't drive it for almost 2 years after owning it for about 6 months.