Question for Jerry Bransford

[Jeff Ca]

Jerry,
I have an 02 Jeep wrangler TJ with a 4.0 automatic transmission, 4" rough country lift with adjustable upper and lower control arms front and rear, SYE, CV Rear driveshaft, 1.25" body lift, 1" Motor mount lift with rough country tummy tuck skid plate. The problem I'm having is a vibration at 28-30 mph. It goes away if I left off the gas or increase speed. I've tried removing the rear drive shaft and putting the jeep in 4h and no vibration. The rear pinion angle has been set at 0 degrees and the front at 2. I have tried everything I know. I currently have the front drive shaft off to see if the vibration was caused by a bad DS, vibration is still there. I have had the rear DS balanced as well. I have also tried different tires and still there. I can only think that it may be caused by the 1'' motor mounts. So I'm looking for some help from the Jeep Guru. Another question I have, if I remove the motor mount lift, can I still use the Rough country high clearance skid plate with a transfer case drop down kit and would that fix possible fix the vibration? Any help would be greatly appreciated.
Thx

 

[tworley]

How are the ujoints?

 

[Jeff Ca]

brand new

 

[pagrey]

Jerry,
...
Thx

Next time send him a PM, He's a nice guy. I bet He'll help you out.

 

[Jamison C]

Next time send him a PM, He's a nice guy. I bet He'll help you out.

New members can’t send PMs until their post count is like 20 I think?

 

[Jeff Ca]

New members can’t send PMs until their post count is like 20 I think?

Yeah, I was trying to get an email or something, so this is the only thing I could try

 

[Jeff Ca]

How are the ujoints?

They are new as well

 

[pagrey]

Yeah, I was trying to get an email or something, so this is the only thing I could try

Guess you know how useful I am here.

 

[Jerry Bransford]

It's doubtful the MML is causing the problem, my TJ has one too without vibrations. That 0 degrees you measured on the rear pinion... you're saying there's a 0 degree difference between the pinion and driveshaft angles? How are you measuring the rear pinion angle?

This is my preferred point from which to measure the pinion angle. By rotating the angle finder 90 degrees from the vertical surface you're measuring from it will directly indicate the pinion angle.

This is how/where I measure my pinion angles from...

Place the angle finder on either of those two flat surfaces circled in yellow. They are exactly 90 degrees from the pinion angle.

Rotating the angle finder as shown below will cause it to directly indicate the pinion angle.

 

[Jeff Ca]

It's doubtful the MML is causing the problem, my TJ has one too without vibrations. That 0 degrees you measured on the rear pinion... you're saying there's a 0 degree difference between the pinion and driveshaft angles? How are you measuring the rear pinion angle?

This is my preferred point from which to measure the pinion angle. By rotating the angle finder 90 degrees from the vertical surface you're measuring from it will directly indicate the pinion angle.

This is how/where I measure my pinion angles from...

Place the angle finder on either of those two flat surfaces circled in yellow. They are exactly 90 degrees from the pinion angle.

View attachment 100256



Rotating the angle finder as shown below will cause it to directly indicate the pinion angle.

View attachment 100257

Yes, that's where we measured from as well

 

[Jeff Ca]

Yes, that's where we measured from as well

It's very frustrating to say the least lol. Logic tells me that it's in the rear since when i removed the rear driveshaft and put the jeep in 4h the vibration went away. But then I had a 4x4 shop tell me that it could be the front DS because there wasn't a load on it??? whatever that means.

 

[Jerry Bransford]

Yes, that's where we measured from as well

Let's get the real guru @mrblaine involved here. Some vibrations are a booger to get rid of but I'm at a loss right now if your rear driveshaft angle is dead-nuts the same as your rear pinion angle. That the vibration goes away when slowing down or speeding up from 28-30 is what's stymying me.

 

[Alex01]

Some jeeps like a bit more angle in the rear. You can add some pinion angle in the rear +-0.5 at a time and see if it helps.

 

[Jeff Ca]

Let's get the real guru @mrblaine involved here. Some vibrations are a booger to get rid of but I'm at a loss right now if your rear driveshaft angle is dead-nuts the same as your rear pinion angle. That the vibration goes away when slowing down or speeding up from 28-30 is what's stymying me.

The vibration is at the mph at goes away when you let off the gas or speed up. Tried it in 2nd gear as well thinking it might be torque converter. So I have a correction, to add, both the ds and pinion angle are at 5.4

 

[mrblaine]

Let's get the real guru @mrblaine involved here. Some vibrations are a booger to get rid of but I'm at a loss right now if your rear driveshaft angle is dead-nuts the same as your rear pinion angle. That the vibration goes away when slowing down or speeding up from 28-30 is what's stymying me.

Nope.

 

[tworley]

What gearing do you have?