Colorado Daily-Driven Trail Warrior V2 - 2006 LJ

[JMT]

Spent some time in the garage this afternoon playing with my Pinion angles.

Ended up adjusting 8 turns out on my Rear Lower Control Arms, so that I could actually utilize my Rear Uppers
(yesterday the Uppers were maxxed as short as they could go)

View attachment 501104


Here's a photo of my rear pinion angle. Roughly 6.5 degrees.

View attachment 501097

As well as my rear Transfer Case angle, measured from two spots, at 5.6 degrees.

View attachment 501099

View attachment 501100

Rear Pinion/Transfer Case angles SEEM to be correct.
(although I'm learning what I'm doing, so I could be botching something completely...)

View attachment 501109


Also adjusted the front to what I THINK is correct...
5.7 degrees on the front pinion

View attachment 501105

Followed by 6.7 Degrees at the front Driveshaft.

View attachment 501106

View attachment 501107


Ultimately, I fixed NOTHING.
The vibrations are STILL there at 65mph, and got no better/worse.
They're the same as they were.

At this point, i'm just uber confused.
With the LJ having the longer rear shaft, I wouldn't think I should be having issues, given the angles of everything.
Nothing is at an "extreme" angle.


I'm thinking it's time I take this entire conversation to a thread of it's own, and let the big-boys duke it out with solutions/theories.

I'm planning to go to Lowes tomorrow, to pick up some washers, just to see if that possibly can cure some issue.
Just not sure where to start, am I putting washers between frame/skid to lower the TCase, or am I putting them between Tcase and skid to raise the TCase?
Any further insight is appreciated!

View attachment 501096

Your front and rear angles are reversed. Typically the rear pinion is 1* lower than the driveshaft and the front pinion is 1* higher than the driveshaft.

Lower the rear pinion to 1* lower than the shaft. Check for vibes. Raise the front pinion 1* above the shaft. Check for vibes. Remove the front shaft. Check for vibes.

 

[zachpeakee]

Unfortunately, I don’t think you can pull the rear D/S with a slip yoke without puking your tcase fluid everywhere.

^^^ had thoughts earlier today to do this, as i'm fairly positive the rear driveshaft is the one causing issue.

It should be just as easy to eliminate it as an issue by pulling the front driveshaft though.
If it still vibrates without a front shaft, the rear is the problem.
If it doesn't vibrate, the rear is not the problem.

I'm a simple creature.

 

[JMT]

I understand the logic, from a 'make profit from the axle' standpoint, but does it not make more sense for selling purposes to KEEP the Dana 44 in the TJ?
Just seems quite a bit more desirable for potential buyers with the Dana 44.

I know when I first bought the Sahara, the Dana 44 was my #1 requirement.
I skipped every listing with a Dana 35 axle, regardless of the price.

How is it an advantage to sell the Dana 44? I don’t see it. You’d have to regear it, s35, what’s the point?

 

[inkedrose]

I just finished page one.....one thing if it's not too late. Get a Dana 35 for the rear and sell the Dana 44. You can get between $1000-1200 for a Dana 44 now. I know you'd have to regear a Dana 35 to 488 but it might be worth it if you do it yourself...

I understand the logic, from a 'make profit from the axle' standpoint, but does it not make more sense for selling purposes to KEEP the Dana 44 in the TJ?
Just seems quite a bit more desirable for potential buyers with the Dana 44.

I know when I first bought the Sahara, the Dana 44 was my #1 requirement.
I skipped every listing with a Dana 35 axle, regardless of the price.

I was just clarifying his statement. I have no idea what the better option would be.

 

[zachpeakee]

Your front and rear angles are reversed. Typically the rear pinion is 1* lower than the driveshaft and the front pinion is 1* higher than the driveshaft.

Lower the rear pinion to 1* lower than the shaft. Check for vibes. Raise the front pinion 1* above the shaft. Check for vibes. Remove the front shaft. Check for vibes.

As you said, the front pinion should be 1* higher than the driveshaft angle.
If that is the case, You're 100% correct, and I botched the adjustments..


I've somehow taken the entire concept and flipped it backwards in my head..
Hence why I set my Front Pinion to 5.7 when my driveshaft is 6.7...Also why my rear pinion is 6.5 when my output shaft is 5.6.

I feel this is one of those moments where I just need to look in the mirror and call myself an idiot a few times.

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As far as the rear pinion is concerned, I shouldn't go 1* lower than the shaft, I should go 1* lower than the transfer case output, correct?
(since I am still on the factory/oem two joint shaft * instead of a CV* )

 

[JMT]

As you said, the front pinion should be 1* higher than the driveshaft angle.
If that is the case, You're 100% correct, and I botched the adjustments..


I've somehow taken the entire concept and flipped it backwards in my head..
Hence why I set my Front Pinion to 5.7 when my driveshaft is 6.7...Also why my rear pinion is 6.5 when my output shaft is 5.6.

I feel this is one of those moments where I just need to look in the mirror and call myself an idiot a few times.

-
-

As far as the rear pinion is concerned, I shouldn't go 1* lower than the shaft, I should go 1* lower than the transfer case output, correct?
(since I am still on the factory/oem two joint shaft * instead of a CV* )

Oh geez, you’re still on a slip yoke?! In that case you match the angle of the pinion and output yoke. Lower picture

 

[Claytone]

You can pull the rear DS and not have leaks. That style of slip yoke is external.

 

[hosejockey61]

I understand the logic, from a 'make profit from the axle and throw money at the LJ' standpoint, but does it not make more sense for selling purposes to KEEP the Dana 44 in the TJ?
Just seems quite a bit more desirable for potential buyers with the Dana 44.

I know when I first bought the Sahara, the Dana 44 was my #1 requirement.
I skipped every listing with a Dana 35 axle, regardless of the price.


To top that off, differential gearing & transmission rebuilds are the two things I am most uncomfortable messing with in a vehicle.
I've done everything in-between, but those two and the extreme tolerances involved send my anxiety through the roof.
SO, it'd be an expensive trip to the re-gear shop to do that.

Not everyone looking at buying it would be interested in taking it offroad or even know the differences between the two axles. It would just be an opportunity to make a few more bucks to put toward your build is all. The re-gearing part eats into that cost, so it wouldn't be worth it unless you did it yourself and even then, only if you could find the gears for cheap.

 

[hosejockey61]

How is it an advantage to sell the Dana 44? I don’t see it. You’d have to regear it, s35, what’s the point?

The option was there if a person had the capability to do it themselves. Not a S35, just regular. Been there done that. In this case though, the juice ain't worth the squeeze for him. I've sold close to a dozen Dana 44's for $1000 each. There is money to be made.

 

[freedom_in_4low]

As you said, the front pinion should be 1* higher than the driveshaft angle.
If that is the case, You're 100% correct, and I botched the adjustments..


I've somehow taken the entire concept and flipped it backwards in my head..
Hence why I set my Front Pinion to 5.7 when my driveshaft is 6.7...Also why my rear pinion is 6.5 when my output shaft is 5.6.

I feel this is one of those moments where I just need to look in the mirror and call myself an idiot a few times.

-
-

As far as the rear pinion is concerned, I shouldn't go 1* lower than the shaft, I should go 1* lower than the transfer case output, correct?
(since I am still on the factory/oem two joint shaft * instead of a CV* )

Yes, you want pinion 0.5-1deg lower than t case output.

 

[zachpeakee]

Oh geez, you’re still on a slip yoke?!

I've only had the LJ for 2 weeks now. I'M MODIFYING/FIXING EVERYTHING AS FAST AS I CAN MAN.

Not everyone looking at buying it would be interested in taking it offroad or even know the differences between the two axles. It would just be an opportunity to make a few more bucks to put toward your build is all. The re-gearing part eats into that cost, so it wouldn't be worth it unless you did it yourself and even then, only if you could find the gears for cheap.

Okay, I get where you're going, and can agree to that to an extent.

I had originally considered keeping the spare 44 when I had them both dropped on the ground, but ultimately decided I could squeeze a bit more money from the sale if it had the Dana 44 in it.

Both of which could be the 'better way to do it'.

Yes, you want pinion 0.5-1deg lower than t case output.

I had my measurements backwards in my head the whole time.
Oh well. I've got the whole day today around the house, so planning to play with it some more here shortly!

Going to pull the front shaft off completely, and get the rear situated before chasing myself in circles trying to adjust both at the same time.

 

[freedom_in_4low]

I had my measurements backwards in my head the whole time.
Oh well. I've got the whole day today around the house, so planning to play with it some more here shortly!

Going to pull the front shaft off completely, and get the rear situated before chasing myself in circles trying to adjust both at the same time.

Basically you're just accounting for a little bit of axle rotation allowed by the bushings under power. It's a bigger deal with leaf springs that allow some spring wrap. With control arms and bushings that don't compress much (like JJs) we probably don't need much at all. I usually shoot for half a degree, myself.

 

[zachpeakee]

Basically you're just accounting for a little bit of axle rotation allowed by the bushings under power.

THAT is where I went wrong yesterday.
I accounted for axle rotation, but set up front/rear backwards of where I should have.

I'll get it right today though.

 

[bobthetj03]

You don't need to remove the front driveshaft completely. That is a pita getting to the yoke bolts with the skid in your way. Just strap/ziptie the shaft up to the frame and tape off the front ujoint so you don't lose the caps. You only need to go for a quick test trip to determine if the front shaft is the issue. Just keep it out of 4WD, lol!

 

[freedom_in_4low]

Just keep it out of 4WD, lol!

I came closer to doing this than I like to admit, once. My hand was on the lever when I remembered my driveshaft was still ratchet strapped to the frame.

 

[zachpeakee]

I removed my front driveshaft earlier.
With that out of the way, I can focus heavily on the rear shaft, and the drivetrain vibrations I'm getting.

Dialed in some new pinion numbers.
Initially I started with 8.4 Degrees at the Output Shaft, and I dialed the Pinion to 7.9 Degrees.
( 0.5 degree difference to account for axle rotation )

However, that did not fix the issue, but did seem to make the vibrations a bit less.

Pulled it back into the garage, and dialed that 0.5 degree difference out.
Making the Output Shaft and Pinion Angle complete parallel to each other.

8.4 Degrees at the Output Shaft , so I settled the rear pinion at 8.4 degrees as well.

I took it for a quick spin, and STILL have vibrations around 65mph.
Although now they are much quieter.

I DID however notice, the vibrations stop completely as soon as I push in the clutch, or throw the shifter into neutral.
Drive 70mph , unload the drivetrain, and all vibrations are gone instantly.

It's a tough day to test the LJ at 65mph, because the fog here is terrible, with about a 300ft range of sight.
So pretty hairy to say the least.

So, with that being said, I'm about to research a little bit, and figure out what the next move should be.

As far as the Transfer Case, and stacking washers, etc is concerned.
I got to thinking about it, and what exactly is the purpose of doing that?

If I stack washers, essentially all that is happening is changing the output shaft angle. At which point I would need to adjust pinion angle.
ALL of which, I can do currently, without stacking washers in random places... am I missing something in my thoughts about that?

 

[freedom_in_4low]

I removed my front driveshaft earlier.
With that out of the way, I can focus heavily on the rear shaft, and the drivetrain vibrations I'm getting.

Dialed in some new pinion numbers.
Initially I started with 8.4 Degrees at the Output Shaft, and I dialed the Pinion to 7.9 Degrees.
( 0.5 degree difference to account for axle rotation )

However, that did not fix the issue, but did seem to make the vibrations a bit less.

Pulled it back into the garage, and dialed that 0.5 degree difference out.
Making the Output Shaft and Pinion Angle complete parallel to each other.

8.4 Degrees at the Output Shaft , so I settled the rear pinion at 8.4 degrees as well.

View attachment 501293

View attachment 501294

I took it for a quick spin, and STILL have vibrations around 65mph.
Although now they are much quieter.

I DID however notice, the vibrations stop completely as soon as I push in the clutch, or throw the shifter into neutral.
Drive 70mph , unload the drivetrain, and all vibrations are gone instantly.

It's a tough day to test the LJ at 65mph, because the fog here is terrible, with about a 300ft range of sight.
So pretty hairy to say the least.

View attachment 501300


So, with that being said, I'm about to research a little bit, and figure out what the next move should be.

As far as the Transfer Case, and stacking washers, etc is concerned.
I got to thinking about it, and what exactly is the purpose of doing that?

If I stack washers, essentially all that is happening is changing the output shaft angle. At which point I would need to adjust pinion angle.
ALL of which, I can do currently, without stacking washers in random places... am I missing something in my thoughts about that?

Remind me, what's your actual driveshaft angle at this point? Should subtract 8.4 from that to determine operating angle of the u joint. Spicer or TW has a chart floating around with maximum shaft rpm vs operating angle.

The fact that it disappears when decoupled from the power train tells me it's torsional, rather than balance related.

How are your u joints? I've had a vibration show up after installing a lift because some old u joints were suddenly being asked to explore ranges of angle that they hadn't seen before.

 

[bobthetj03]

I'm certainly no expert, but ujoints have a critical operating angle. You exceed that and they don't like it. Lowering the angle that the drivetrain is at also lowers the ujoint's operating angle. Picture your engine/trans/t-case as one unit with the motor mounts as the fulcrum point. Spicer has some good info on this.

 

[JMT]

I DID however notice, the vibrations stop completely as soon as I push in the clutch, or throw the shifter into neutral.
Drive 70mph , unload the drivetrain, and all vibrations are gone instantly.

Drop the pinion 1*. Under load it raises the pinion 1*, so if your vibe free when it’s not under load you may just need to drop pinion 1*

 

[zachpeakee]

Remind me, what's your actual driveshaft angle at this point? Should subtract 8.4 from that to determine operating angle of the u joint. Spicer or TW has a chart floating around with maximum shaft rpm vs operating angle.

Driveshaft angle is 13.6 Degrees.

How are your u joints? I've had a vibration show up after installing a lift because some old u joints were suddenly being asked to explore ranges of angle that they hadn't seen before.

As far as I can tell, the U Joints are in good shape. I'm feeling no slop/play or binding in them.
At this point, I'm not ruling them out entirely...

Drop the pinion 1*. Under load it raises the pinion 1*, so if your vibe free when it’s not under load you may just need to drop pinion 1*

This was my thought.
However, when my pinion WAS dropped to 7.9* (0.5 degrees low) the issue was the exact same.

So i'm not entirely sure, but I'm willing to drop it a full degree, just to entertain the idea of that fixing the issue.

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I made a stand-alone thread for the entire issue.
https://wranglertjforum.com/threads/figuring-out-my-driveline-vibrations-after-4-lift.76669/

I wanted to keep it all in this build thread, but feel at this point its going DEEP, and we'll soon fill up 5 pages of build-thread with pinion chit-chat.
not to mention, the additional responses could lead to some interesting theories as to what the issues might be.