Vibes vibes vibes!!

[7slotMT]

Yes another vibes thread, but unlike most of these... I feel like I have mostly dotted my i's and crossed my t's. Getting vibes around 40mph on up.

2004 TJ with a 4" currie lift. I have an SYE and double cardan. I got the front end dialed in using Nate's YouTube video on using lasers and whatnot to get everything centered. Jeep steering feels better than it ever has.

Toe is at 1/16". I ended up pulling the front driveshaft to make sure I wasn't feeling vibes from the wrong area.

Caster is at 5.5 degrees.

Rear double cardan driveshaft is at 17.5 and pinion is at 16.5 degrees - verified with digital angle finder. Have messed around between set equal to each other and as far as the pinion 2 degrees lower in .5 degree increments.

Ran the Jeep today on jack stands with my cellphone on a tripod below. Can feel slight vibes around the same parameters but not the same as being on pavement. Video was no help in locating anything.

At this point my mind went to either wheel bearings or motor mounts. Checked for play in the wheel bearings and they seem fine.
I went with LJ rear springs and TJ heavy duty fronts, so without any heavy weight in bumpers and a winch it seems my lift is around 5" true. Where is the next logical place to look? I know if I do a MML and body lift I would be reducing the tcase by around +/- 3 degrees?

Experts, please send help!

 

[JMT]

What gears?
What tire size?
Toe in at 24” diameter should be 1/8” to maintain factory 0.30*
Have you removed the rear driveshaft to see if the vibes go away?
Rear pinion looks a few degrees high.

 

[NskLJ]

In the picture you posted your pinion looks high (more than 1 degree), did you use a socket to check the angle off the cap of the u joint? Does the vibration go away at higher speeds?

 

[7slotMT]

What gears?
What tire size?
Toe in at 24” diameter should be 1/8” to maintain factory 0.30*
Have you removed the rear driveshaft to see if the vibes go away?
Rear pinion looks a few degrees high.

That is interesting. I'm obviously gonna have to check that in the morning but I'm thinking the wide angle on the cell phone is distorting things here. I'll post a better picture in the morning.

I have not pulled the rear and ran the front only yet. Sounds like my next step.

Gears are stock 3.07 with an NV3550 and I measured 1/16 at 30" per Mrblaines suggestion. I am planning on running a Ford 9 and Dana 44 combo so I have been getting by with stock gears while I build those.

 

[7slotMT]

In the picture you posted your pinion looks high (more than 1 degree), did you use a socket to check the angle off the cap of the u joint? Does the vibration go away at higher speeds?

That is definitely interesting but I'm wondering if the wide angle on my S21 is distorting the picture here. I measured from the flat on the backside of the axle and on top of the drive shaft for my measurements. The vibes do not go away at higher speeds.

 

[Blackjack]

Pinion is a little high but the bigger problem I see is that you have a cap spinning in the tcase yoke. You need to get that shaft and the tcase yoke checked out.

 

[7slotMT]

Pinion is a little high but the bigger problem I see is that you have a cap spinning in the tcase yoke. You need to get that shaft and the tcase yoke checked out.

Wow good eyes there! I just had this shaft rebuilt within the last year when I put the SYE in... Looks like the shaft is coming back out! Likely this would be a shaft problem and not a yoke problem though?

 

[Blackjack]

Wow good eyes there! I just had this shaft rebuilt within the last year when I put the SYE in... Looks like the shaft is coming back out! Likely this would be a shaft problem and not a yoke problem though?

Could be either or both. Spinning caps wear away the tabs that keep the joint centered. Pinion angle vibes are present either on acceleration or deceleration depending on if high or low. Balance vibes will occur in a rpm(speed) range say 45-55 mph. Vibes that start and stay more often than not indicate loose or worn parts.

 

[Gollywomper]

Is it a constant vibration or pulsing harmonic type? Have you removed the front then rear driveshafts to isolate where the vibrations are coming from?

 

[7slotMT]

Is it a constant vibration or pulsing harmonic type? Have you removed the front then rear driveshafts to isolate where the vibrations are coming from?

Its pretty constant above 40mph. I've pulled the front but not the rear yet. Blackjack pointed out that I have some interesting things going on with you ujoint that I didn't notice so I will probably start there.

 

[7slotMT]

So since this last post, I have installed a MORE MML, a Savvy body lift, Ford 9 inch rear axle and have continued to fight vibrations no matter what the angle on the pinion is set at. I just had the Jeep into an offroad shop to get it professionally aligned, and they also couldnt get rid of the vibes and suggested dropping the lift height to 3" from 4-4.5" (need to measure). I have a standard length JB conversions SYE, thinking that the super short could help here, but honestly I think I'm going to start with a transfer case drop since it's cheap and see if the vibrations subside.

Think 3/4 drop would be enough here, or should I go bigger?