Diff or Wheel bearing noise?

[89Vette]

Today, I noticed there's some vibration as it's revved in park -- especially when cold. Though it's possible a tune-up (or injector service) is necessary, it's not really a miss. I'm still thinking bearing(s). I confirmed this by kicking it out of gear on the hwy too. The effect directly corresponds to engine revs.

Because I'm also hearing a bit extra noise at startup, I'm leaning toward an engine accessory bearing issue. It's [somewhat] reduced after warm-up.

As I said, engine noise seems the primary cause. Remember my post asking about air pump noise? I took it by an Isuzu service facility today. Tech took a quick listen. Immediately, he said intake gasket(s) leak. I asked if that would account for roughness at 2500. He also said motor mounts could be part of the issue.

This could be a combo of all 3. A little gear noise, a little mount vibration, and an accentuation by the intake (to create an imbalance in cylinder power).

Are intake gaskets really a [common] problem on these? The tech said it was a problem in general with the 3.5L motor.

[technocoy]

Just my 2 cents, but I feel like in general that the VX has a certain roughness to it. I remember when I first got mine (25,000 miles) that I for the longest time was thinking there was a bearing or a gears, etc that may be worn because of a whine or rub sound i was hearing when letting off or under certain rolling conditions.

With it not getting any worse and having grown used to it, it now seems normal, but when I drive my wife's pilot or another, more "civilized" vehicle it becomes evident when I go back to the VX that it's a bit more beastly than other cars.

It's also a bit rougher and louder in the higher RPMs than other SUVs, etc.

So, I don't want to lull you into buying something that may have issues, but the fact you have heard the same thing in three different VXs has me thinking you are experiencing the same thing I did.

Even my best friends JGC seems quiet in comparison.

Throw some dynamat in it and call it a ride!!!

Good luck.

[89Vette]

Just my 2 cents, but I feel like in general that the VX has a certain roughness to it. I remember when I first got mine (25,000 miles) that I for the longest time was thinking there was a bearing or a gears, etc that may be worn because of a whine or rub sound i was hearing when letting off or under certain rolling conditions.

With it not getting any worse and having grown used to it, it now seems normal, but when I drive my wife's pilot or another, more "civilized" vehicle it becomes evident when I go back to the VX that it's a bit more beastly than other cars.

It's also a bit rougher and louder in the higher RPMs than other SUVs, etc.

So, I don't want to lull you into buying something that may have issues, but the fact you have heard the same thing in three different VXs has me thinking you are experiencing the same thing I did.

Even my best friends JGC seems quiet in comparison.

Throw some dynamat in it and call it a ride!!!

Good luck.

Ask yourself if people would have paid $30k for the level of roughness/vibration you're talking about. Ask yourself again if the problem might have occurred on yours before the 25k mileage point? Certain vehicles do have "characteristics". But engineering, parts, part failures, and other aspects play a part in the final result.

Generation 1 JGCherokee's definitely have a problem with their differential bearings. They are louder and fail in a high percentage of cases. If the result is normally vibration/loudness vs breaking down, people could come to the conclusion it's just a characteristic of the vehicle. To me, it was a problem.

Again, I'm imagining what a new specimen would have felt like. Whether this is primarily the intake manifold problem, wheel bearing vibration, differential vibration, or other drivetrain bearings, it's something that could be found and improved. Or,,,you could say "Eh...whatever."

FWIW,,,the Isuzu tech did say manifold gaskets were problematic on the 3.5L motor. Whether it's true and/or he was blowing smoke, I don't know. Guess I could do a search or post a thread on that topic.

Considering how much more forgiving injection might make manifold leaks, maybe it is an issue (with the VX)? The tech called the gaskets "cheap plastic". Maybe FelPro or some other manufacturer makes a better set. Regardless, I'm trying to decide/learn how likely a manifold leak could feel like a vibration vs a miss. Maybe at just the right amount of cylinder imbalance -- just short of a lean miss??? I did also note an idle very close to an outright miss when it gets hot. I suspect this is a real issue. (Maybe it explains why the mpg is so bad (worse) for some owners?)

BTW: Compared to other 4x4 setups/brands I've driven, this Isuzu design does seem to have it's share of gear whine/drag. When you let off the gas, you can feel the drivetrain dragging the vehicle slower than other 4x4 system (i.e., Quad-Trac II or AWD car). It has more of the character of a truck,,,big truck,,,maybe even a BEAST. Probably part of the reason for the "Little Beast" nickname. Had I not noticed the pronounced vibration in park revving the motor, I might have come to the same conclusion.

I also found a thread on fan bearings causing this problem. So there are multiple possibilities. There are also multiple perceptions that could be formed from verbal description vs actual 1st-hand experience of individual symptoms.

[nfpgasmask]

That's weird because I never ever heard this noise, but as soon as I lifted, it was there.

Bart

[technocoy]

Ask yourself if people would have paid $30k for the level of roughness/vibration you're talking about. Ask yourself again if the problem might have occurred on yours before the 25k mileage point? Certain vehicles do have "characteristics". But engineering, parts, part failures, and other aspects play a part in the final result.

Generation 1 JGCherokee's definitely have a problem with their differential bearings. They are louder and fail in a high percentage of cases. If the result is normally vibration/loudness vs breaking down, people could come to the conclusion it's just a characteristic of the vehicle. To me, it was a problem.

Again, I'm imagining what a new specimen would have felt like. Whether this is primarily the intake manifold problem, wheel bearing vibration, differential vibration, or other drivetrain bearings, it's something that could be found and improved. Or,,,you could say "Eh...whatever."

FWIW,,,the Isuzu tech did say manifold gaskets were problematic on the 3.5L motor. Whether it's true and/or he was blowing smoke, I don't know. Guess I could do a search or post a thread on that topic.

Considering how much more forgiving injection might make manifold leaks, maybe it is an issue (with the VX)? The tech called the gaskets "cheap plastic". Maybe FelPro or some other manufacturer makes a better set. Regardless, I'm trying to decide/learn how likely a manifold leak could feel like a vibration vs a miss. Maybe at just the right amount of cylinder imbalance -- just short of a lean miss??? I did also note an idle very close to an outright miss when it gets hot. I suspect this is a real issue. (Maybe it explains why the mpg is so bad (worse) for some owners?)

BTW: Compared to other 4x4 setups/brands I've driven, this Isuzu design does seem to have it's share of gear whine/drag. When you let off the gas, you can feel the drivetrain dragging the vehicle slower than other 4x4 system (i.e., Quad-Trac II or AWD car). It has more of the character of a truck,,,big truck,,,maybe even a BEAST. Probably part of the reason for the "Little Beast" nickname. Had I not noticed the pronounced vibration in park revving the motor, I might have come to the same conclusion.

I also found a thread on fan bearings causing this problem. So there are multiple possibilities. There are also multiple perceptions that could be formed from verbal description vs actual 1st-hand experience of individual symptoms.

Not hearing your specific issue it's hard to know.

As for paying 30,000 for the vehicle you bring up an interesting point. Point being that no, not many people were willing to pay that much and that led to brand new VXs on lots for low and mid 20s. It's a concept vehicle that earned a short run being hand assembled. It's not an infiniti luxury vehicle.

I would say that yes, it IS possible some damage occurred prior to 25,000 miles, but seeing as how I've put another 55,000 on it with no issues I probably would say "meh, whatever".

That's not the point though, the point is that I've driven at least 6 differenct VXs one of them showroom new and they all have a rough and tumble running demeanor.

Now that being said, mine isn't exceptionally loud as some have described, but it does feel harder than other vehicles I've driven and owned.

Keep in mind that despite the cost, this is a specialty halo vehicle. There are no cupholders, etc. This was expensive because it was limited and advertised as essentially a consumer rally vehicle. It wasn't expensive because it was a smooth ride. I mean, my wife won't even ride in it it's so rough and I have Nitto Street tires on mine.

I don't doubt that there is an issue necessarily, I just think that coming from other cars to the vehicross takes some adjustment. If you keep looking for a problem on different cars and can't seem to pinpoint it it may just not be a problem. I would have to think that after you have driven several and they all have the same thing it's probably not something specifically wrong as much as it is a characteristic.

I do think I've seen several posts on here about issues with the gasket as well. A search will most definitely turn something up there.

If it's driving you that nuts, it may just not be the car for you.

Good luck! I hope you find one. I love my VX more than some of my family members.

[wintermute]

I love my VX more than some of my family members.

Me too!

[89Vette]

Family members are one thing....How bout your wife, girlfriend, or mistress? LOL

Seriously, anyone reading this thread, go start your VX. Slowly run rpms from idle to 2500rpms. Tell me if it stays smooth or gets rough. (If it gets rough, you'll feel it in the steering wheel and gas pedal.) To me, it feels like bearing vibration.