Driveline vibration

[MTBooth]

Hi guys. I’ve been having a vibration since purchasing the vehicle about a year ago and can’t figure out what it is. Some facts about my Jeep that would pertain to the vibration:

• 2005 Jeep Wrangler TJ
• 2in BDS suspension lift
• Front u-joint and tires were changed which didn’t help.

Vibration:

• Feel it through my seat and floor approx between 50-60 mph
• Only feel it when giving it gas. It goes away instantly when I let go of the gas.
• Feel it most when RPMs are low and when going up hill.
• Can hear a vibration.

 

[Jerry Bransford]

Suspension lifts can cause a vibration from the excess angle at the rear driveshaft u-joints they create. Does your Jeep have a dropped transfer case skidplate or anything else that is commonly installed to eliminate vibrations?

 

[MTBooth]

Suspension lifts can cause a vibration from the excess angle at the rear driveshaft u-joints they create. Does your Jeep have a dropped transfer case skidplate or anything else that is commonly installed to eliminate vibrations?

It had a 1inch transfer case drop and still had a vibration which I removed after adding a 1inch brown dog MML... still has the vibration though.

 

[MTBooth]

Suspension lifts can cause a vibration from the excess angle at the rear driveshaft u-joints they create. Does your Jeep have a dropped transfer case skidplate or anything else that is commonly installed to eliminate vibrations?

My mechanic said I should add a SYE and rear adjustable control arms but I would like to get other people’s opinions before shelling out the money. I recently added a 1.25 in JKS body lift, 33in tires and regeared to 4.56 ratio and Rancho 5000x shocks. All of which had no effect on the vibration.

 

[Rob5589]

You can try about 1/4" of washers between the frame and skid. If that doesn't work, a sye should.

 

[Jerry Bransford]

Installing a SYE also requires that a replacement rear aftermarket driveshaft also be installed. But for only a 2" suspension lift neither of those is required. Has anyone somehow changed the angle of the rear axle's pinion angle trying to cure the vibration? Were cam bolts ever installed onto the upper-rear control arms that makes them adjustable?

For a 2" suspension lift a 1/2" to 1" tcase drop is normally more than enough to eliminate vibrations. Same with a 1" MML. Something else is going on to cause those vibrations since they remained after installing one then the other. Perhaps a bad u-joint on the rear driveshaft but it's hard to tell.

Is your rear axle's pinion angle still as the factory set it?

 

[Mike_H]

Have you checked the u joints in the drive shafts? They will vibrate as you describe when they are bad.

 

[MTBooth]

Have you checked the u joints in the drive shafts? They will vibrate as you describe when they are bad.

Installing a SYE also requires that a replacement rear aftermarket driveshaft also be installed. But for only a 2" suspension lift neither of those is required. Has anyone somehow changed the angle of the rear axle's pinion angle trying to cure the vibration? Were cam bolts ever installed onto the upper-rear control arms that makes them adjustable?

For a 2" suspension lift a 1/2" to 1" tcase drop is normally more than enough to eliminate vibrations. Same with a 1" MML. Something else is going on to cause those vibrations since they remained after installing one then the other. Perhaps a bad u-joint on the rear driveshaft but it's hard to tell.

Is your rear axle's pinion angle still as the factory set it?

I’m not sure about the rear axle pinion angle. I’ll have to check. But to get a very rough idea of the angle, heres a picture.
I just spoke to the previous owner, he said the vibration started about 3 years after the lift. That’s when he replaced the t-case and installed a 1 inch transfer case drop which seemed to help the vibration but not solve it. He never did the cam bolts.

 

[Jerry Bransford]

From that photo the pinion angle looks too high. Are there adjustable length upper control arms installed?

 

[Blackjack]

Acceleration vibration is most often a symptom of the pinion angle being too high. From you pic that would appear to be the case. You can try lowering the tcase a 1/4 inch at a time or you will need adjustable upper arms to go shorter than stock to lower the pinion angle some.

 

[MTBooth]

From that photo the pinion angle looks too high. Are there adjustable length upper control arms installed?

No all stock control arms.

 

[MTBooth]

Acceleration vibration is most often a symptom of the pinion angle being too high. From you pic that would appear to be the case. You can try lowering the tcase a 1/4 inch at a time or you will need adjustable upper arms to go shorter than stock to lower the pinion angle some.

I tried the t case drop which did not fix it. Would you need lower adjustable control arms or only the upper?

 

[Jerry Bransford]

I'd remove the rear driveshaft and take a look at the u-joints on the rear driveshaft, a bad driveshaft u-joint can cause a vibration. There should be no red dust (rust) coming out of the u-joint bearing caps and there should be absolutely no slop or sideways movement between the u-joint body and its bearing caps when you move them around with your hands.

Then without reinstalling the driveshaft, shift into 4Hi and drive around to confirm that the vibrations go away with the rear driveshaft gone. That will at least isolate the problem to being rear driveshaft/pinion related or not.

 

[Blackjack]

I tried the t case drop which did not fix it. Would you need lower adjustable control arms or only the upper?

I prefer uppers for making angle adjustments (pinion and caster) and use the lowers for wheelbase and squaring axle to the frame (thrust angle) .

 

[MTBooth]

I'd remove the rear driveshaft and take a look at the u-joints on the rear driveshaft, a bad driveshaft u-joint can cause a vibration. There should be no red dust (rust) coming out of the u-joint bearing caps and there should be absolutely no slop or sideways movement between the u-joint body and its bearing caps when you move them around with your hands.

Then without reinstalling the driveshaft, shift into 4Hi drive around to confirm that the vibrations go away with the rear driveshaft gone. That will at least isolate the problem to being rear driveshaft/pinion related or not.

Thank you so much. I will keep you posted!

 

[AndyG]

Listen to Jerry and and get the good Spicer u joints ..even if they don't solve the vibe , you want them .

 

[MarvinL]

I don't know if this will help....... I had a vibration that ended up being a little slop side to side where the drive shaft clamps to the pinion which allowed it to become off centered on the pinion. I second what everyone else has been saying tho check your u joints first.

 

[MTBooth]

Hey guys,

I know this is an old thread but just wanted to update on the current situation.
I changed the read drive shaft u-joint and it continues to have the vibes . Again around 40-50 mph and then will go away. Should I bite the bullet and get rear adjustable control arms?

 

[Goatman]

Did removing the rear shaft and driving in 4h eliminate the vibe? If yes, then you need to get adjustable arms to get your pinion angle aligned. If you ever plan on going with more spring lift then suck it up and get a SYE and new shaft so you won't have to deal with this problem again.
If driving around on the front driveshaft did not eliminate the vibe, reinstall the rear shaft and then pull the front shaft. See if this cures the vibe. If it does, then you know to check front ujoint and centering cup.

 

[MTBooth]

Did removing the rear shaft and driving in 4h eliminate the vibe? If yes, then you need to get adjustable arms to get your pinion angle aligned. If you ever plan on going with more spring lift then suck it up and get a SYE and new shaft so you won't have to deal with this problem again.
If driving around on the front driveshaft did not eliminate the vibe, reinstall the rear shaft and then pull the front shaft. See if this cures the vibe. If it does, then you know to check front ujoint and centering cup.

Ok I will try to pull the rear shaft over the weekend. I’ll keep you posted. Thank you!