Shotts' 1997 Lexus "Rock Crawler" buildup:

[ShottsCruisers]

OK...it's ALMOST DUNNNNN! Here's the latest:

ARB Lockers installed
4.88 gears installed (I'M GLAD I DID THIS!)
1-inch added front lift to correct the front pinion angle for the D/C driveshaft.
(5+ inches front/4.5 inches rear)

We're still chasing vibration. Experts think it might be rear pinion angles or worn rear U-joints. I've got a lot of great ideas on MUD and am checking them out.

Here's the latest info. Click this link then NEXT to cycle through the 6 or so new pics. http://shottscruisers.smugmug.com/gallery/916576/3/54505973

 

[upcruiser]

That thing is coming along nicely! What are your plans for it? I mean, what are you planning to use it for? Are you doing the installs yourself?

Man, I want to do an ARB locker install so bad. If I had the money I'd order me a set asap. I've got my front axle apart right now, wish I could just drop the setup in front and rear while the truck is out of commision.

 

[ShottsCruisers]

That thing is coming along nicely! What are your plans for it? I mean, what are you planning to use it for? Are you doing the installs yourself?

Man, I want to do an ARB locker install so bad. If I had the money I'd order me a set asap. I've got my front axle apart right now, wish I could just drop the setup in front and rear while the truck is out of commision.

It'll be our dedicated trail vehicle. The 100 will be used for trips and moderate 4-wheeling. This Lexus will sit until trail time. :ylsmoke:

In tracking down vibration I discovered the truck is leaning F&R by 1/2 inch. The driver's side lift is less. Time to trim pack again.

 

[goodtimes]

John, if you suspect it is rear u-joints, or inappropriate u-joint angles, just remove the rear driveshaft, and take it for a spin in front wheel drive. You can do that it a 'cruiser, right? (I don't remember if they put a real transfer case in those things or not).

When you get it ready for the trail, let me know. My boss owes me a weekend off, so if you give me a weeks notice, I can get the time off to come see you wet your pants when we point that thing towards the sky a time or two. hehehe....

OH, to the "hours on upper ajax" comment from a month or two ago (few posts up in this thread), I have been through there with 4 vehicles (including my stock rubicon), in less than 1.5 hours. It's all in knowing where to put the tires, then putting them there.

 

[BMAN]

Hey what's the story on this pig? When are we gonna make that Woodpecker trip?

 

[ShottsCruisers]

John, if you suspect it is rear u-joints, or inappropriate u-joint angles, just remove the rear driveshaft, and take it for a spin in front wheel drive. You can do that it a 'cruiser, right? (I don't remember if they put a real transfer case in those things or not).

When you get it ready for the trail, let me know. My boss owes me a weekend off, so if you give me a weeks notice, I can get the time off to come see you wet your pants when we point that thing towards the sky a time or two. hehehe....

OH, to the "hours on upper ajax" comment from a month or two ago (few posts up in this thread), I have been through there with 4 vehicles (including my stock rubicon), in less than 1.5 hours. It's all in knowing where to put the tires, then putting them there.

Rear shaft is out and vibration is better. One of the U-joints is worn badly. I'll replace them and re-try....BUT.....with only the front shaft in (pretty good pinion angle and a D/C shaft) it still vibrates when on the gas, more the faster you go, and it has a rough spot from 35-45MPH. ?????

 

[Scott Brady]

could be influenced by worn motor/gearbox mounts too.

That truck is pretty tall. It will be a challenge to rid of all vibration IMO without significant expense.

 

[ShottsCruisers]

could be influenced by worn motor/gearbox mounts too.

That truck is pretty tall. It will be a challenge to rid of all vibration IMO without significant expense.

Well, I am growing weary. I thought those rear arm adjusts to correct the pinion angle would do. Not so far. We're pretty close to being identical in angle. We'll square it up with the shaft out. It is possible we got a bad DC front shaft. 4 Wheel Supply commented about that though I don't know if they were guessing or not.

 

[goodtimes]

How bad is the "rough spot"? Is it repeatable? Under what conditions? (speed, load on the engine, road conditions, etc).

There is a possibility that you are running into a harmonics issue. Every mechanical component gives off a certainn amount of energy as vibration. Generally, there are so many different components giving off so many different vibrations at so many different frequencies and so many different intensities and phaze angles, that a standing wave will not form because they are on different phazes. Basically they cancel each other out. You have changed some of those frequencies, intensities and phaze "angles", so they may be getting close to forming a standing wave at a certain point your "rough spot". (A classic example of this is "death wobble" common on short wheelbase jeeps). As Scott mentioned, this can be a major pain to solve, and often times comes down to a crap shoot. You just start changing parts until the problem goes away since there is no realistic way to test the components to a level of 95% confidence without "considerable expense" as Scott puts it.

A second comment is that you *are* building what you call a dedicated trail rig. One of the major advantages of having a dedicated trail rig is the fact that minor clunks, rattles, vibrations etc., which would be annoying on a daily driver, can be lived with. You should go for a ride in my jeep sometime. After that, you probably won't even feel the little "rough spot" in the lexy. hahaha

 

[ShottsCruisers]

How bad is the "rough spot"? Is it repeatable? Under what conditions? (speed, load on the engine, road conditions, etc).

There is a possibility that you are running into a harmonics issue. Every mechanical component gives off a certainn amount of energy as vibration. Generally, there are so many different components giving off so many different vibrations at so many different frequencies and so many different intensities and phaze angles, that a standing wave will not form because they are on different phazes. Basically they cancel each other out. You have changed some of those frequencies, intensities and phaze "angles", so they may be getting close to forming a standing wave at a certain point your "rough spot". (A classic example of this is "death wobble" common on short wheelbase jeeps). As Scott mentioned, this can be a major pain to solve, and often times comes down to a crap shoot. You just start changing parts until the problem goes away since there is no realistic way to test the components to a level of 95% confidence without "considerable expense" as Scott puts it.

A second comment is that you *are* building what you call a dedicated trail rig. One of the major advantages of having a dedicated trail rig is the fact that minor clunks, rattles, vibrations etc., which would be annoying on a daily driver, can be lived with. You should go for a ride in my jeep sometime. After that, you probably won't even feel the little "rough spot" in the lexy. hahaha

Answers:

Par 1: Every time you're at 35-50 or so the vibration is more like a low-pitched shudder. It's irritating. Gotta get rid of it. It's not there with the front shaft out and the rear in.

Par 2: Can't live with it for 2 reasons....1. If the thing doesn't drive like a Lexus it'll defeat the purpose for which I bought it...to leave the 100 home. 2. Because vibration wears other parts out. I don't want an unreliable Cruiser.

 

[Scott Brady]

John,

It can most definitaly be fixed. Just realize that it might cost you some $$$ before it is all over with .

 

[ShottsCruisers]

Spoke to Slee just now. He told be to take a DEEP BREATH (by having a beer....didn't do it) and relax. There more things that need to be checked to troubleshoot this. I'm sending him my DC front shaft to have checked. I am replacing my U-joints and will get the rear shaft balanced.

ANYBODY KNOW WHERE IN TUCSON?

Then wait to hear back from Slee about my front shaft. Meanwhile the stock front is going back in. I'm worn out. :ar15:

 

[Scott Brady]

John,

You are building a vehicle at the extreme end of its operating tolerances. Large tires, huge lift, etc.

These custom project ALWAYS have challenges. You should not expect it to be easy or cheap.

It is just the nature of the beast amigo, so dont get frustrated. Christo is as good as they come, he will help you solve the problem.

 

[ShottsCruisers]

You should not expect it to be easy or cheap.

Ya....except that they sell the stuff as a "bolt-in" kit. :smilies27

I do understand though how defferent aged vehicles can have differently worn parts and therefore this happens when you're at these angles. If I could do it again I'd a stuck at the go-anwhere on earth 3.5 or so inches like my '93. :campfire:

 

[Scott Brady]

If I could do it again I'd a stuck at the go-anwhere on earth 3.5 or so inches like my '93. :campfire:

That sounds like an echo