Vibration after changing from 3.07 to 4.10 gears

[nacra780]

Just had gears changed from 3.07 to 4.10. Have a vibration that starts at 55 mph and gets worse up to 70 mph. Have not taken it higher than that. Vibration remains if I push the clutch in and remove the load.

I just replaced the drive shaft thinking it may be imbalance, no change. I isolated this to the rear by removing the rear driveshaft, issue went away.

There are two things I was going to try next, but would appreciate input on dealing with this. The drive shaft is new, but it is the standard type, not CV. These things are an attempt to get the transfer case and pinion angles the same. The current measurements are:
Transfer case = 9
Drive Shaft = 12
Pinion = 11

The skid plate is already dropped about 1/2 to 3/4". Had to do this after the 2.5" lift to solve vibrations even though I have a MML. I may try to drop it more, but not sure I can make up the angle difference.

Use rear adjustable control arms, upper, lower, or both, to move the pinion down 2 degrees. Will this make the driveshaft angle too large? Any other issues with this ideal?

SYE setup is planned for this winter. Don't want to spend the money or have the jeep down for that long right now. I say a long time because I plant to rebuild the transfer case when I have it apart.

Any advise would be appreciated.

05 Jeep X
33" Tires
OME 2.5" Lift, 1.25" BL, 1" MML
6 speed manual, NGS370
4.0L

 

[bobthetj03]

With the standard 2 ujoint ds you want the output yoke of the t-case parallel with the pinion yoke of the rear ds. So, based on your measurements, it looks like you need to lower the rear pinion 2*. This may or may not exceed the ujoints operating angles, added with the faster ds revolutions post re-gear, you may not be able to dial them out without a SYE/DCDS. The other option would be to drop the t-case 2* to match your current pinion angle. That may get you by till SYE time.

 

[Gollywomper]

Very common. Seems like you have a grasp on causes and fixes. When I was troubleshooting my vibrations I did the same. Removed rear DS and vibes went away. However the problem was not my rear DS. It was the front DS. But when running it under load it reduced the vibes. It’s easy to isolate. You can just unbolt front DS from axle and tie it up to the frame. Just be sure you’re in 2wd.

 

[ranger101]

Very common. Seems like you have a grasp on causes and fixes. When I was troubleshooting my vibrations I did the same. Removed rear DS and vibes went away. However the problem was not my rear DS. It was the front DS. But when running it under load it reduced the vibes. It’s easy to isolate. You can just unbolt front DS from axle and tie it up to the frame. Just be sure you’re in 2wd.

Maybe I’m overthinking this, but it’s a live axle setup. Won’t the front shaft be spinning even when he’s in 2wd?

 

[Gollywomper]

Maybe I’m overthinking this, but it’s a live axle setup. Won’t the front shaft be spinning even when he’s in 2wd?

Yes. But it’s not under the same load as when in 4wd. When disconnected from axle it doesn’t spin when in 2wd.

 

[ranger101]

Yes. But it’s not under the same load as when in 4wd. When disconnected from axle it doesn’t spin when in 2wd.

Good bit of info to know

 

[nacra780]

On the front ds idea, I unloaded the ds by pushing in the clutch. Vibration did not go away. Let me know if I am missing something. Don't want to rule out any potential causes.

Will try lowering the skid this weekend. What is the limit of how low I can go with it?

Thanks for the suggestions.

 

[Gollywomper]

On the front ds idea, I unloaded the ds by pushing in the clutch. Vibration did not go away. Let me know if I am missing something. Don't want to rule out any potential causes.

Will try lowering the skid this weekend. What is the limit of how low I can go with it?

Thanks for the suggestions.

pushing in the clutch does nothing for the drive shafts. They are still spinning from the axles rotating. The front is being turned from the wheels spinning not engine power.
If you are rolling then both drive shafts will be spinning.

 

[nacra780]

Ok, will try with front ds out. Not hard to do.
Thanks

 

[Gollywomper]

Ok, will try with front ds out. Not hard to do.
Thanks

I am just relaying my experience. I found it odd, too that the vibes mostly went away with rear ds removed in my rig. Fought it for a while. But found it to be my front. So I recommend to drive with each one out to verify exactly where the issue lays.

 

[bobthetj03]

One ds or another can act like a tuning fork with both are connected to the t-case, so you can remove one or the other and cure the vibe, but attach them both and vibes. It's a tough diagnosis. I've seen t-case skids go as low as 1.5", so you should be able to go at leas that much. shift linkage will suffer.

 

[Brianj5600]

I'm with Bob. Try lowering the pinion. It needs done whether or not it fixes the vibration.

 

[nacra780]

Gollywomper was dead on. Removed the front ds and took it to 75 mph, no vibration. Now what is the rest of the story? Will check front angles tomorrow. I do have adjustable lowers on the front.

 

[Gollywomper]

Gollywomper was dead on. Removed the front ds and took it to 75 mph, no vibration. Now what is the rest of the story? Will check front angles tomorrow. I do have adjustable lowers on the front.

Crazy how the vibrations from the front changes under load vs no load. Glad ya got it narrowed down.
This is why my Yukon hub kit will be here tomorrow.

 

[Chris]

If it's the dreaded harmonic vibration, there is only one person (that I know of at least) who has 100% solved it, and that is @psrivats. He didn't solve it himself of course, but he spent 6 months with a number of different shops looking for the solution. It was a drivetrain shop here in Portland, Oregon who did some active balancing and cured it 100%.

@psrivats has a huge thread about this on the forum.

 

[Gollywomper]

If it's the dreaded harmonic vibration, there is only one person (that I know of at least) who has 100% solved it, and that is @psrivats. He didn't solve it himself of course, but he spent 6 months with a number of different shops looking for the solution. It was a drivetrain shop here in Portland, Oregon who did some active balancing and cured it 100%.

@psrivats has a huge thread about this on the forum.

Yes I believe all of them can be cured, with enough time and money.

 

[Chris]

Yes I believe all of them can be cured, with enough time and money.

They can indeed. The other issue is finding someone who knows what they are doing. I believe that often times the issue is that as oppose to looking for individual components that are “worn”, the vehicle or drivetrain needs to be balanced as a whole.

 

[psrivats]

As Blaine says, you have to systematically and thoroughly check every thing in the drivetrain. There are no shortcuts sadly. It can take 6 months or two years and still continuing like other folks on the forum.

 

[bobthetj03]

As Blaine says, you have to systematically and thoroughly check every thing in the drivetrain. There are no shortcuts sadly. It can take 6 months or two years and still continuing like other folks on the forum.

2 years, or longer depending on resolve, finance, and patience.

 

[Gollywomper]

I have been able to get mine down to a minimum. However after driving without my front DS, while it was being rebalanced, I really like the way it drove and how smooth it was. So rather than continue to fight it I decide to purchase the hub kit. Hubs may or may not be the answer for others, but I am surprised more folks aren’t running them.