MML - Vibration: Is there a correlation?

[nfunlimited]

So here I am again with technical question. Everyone must think I am the most particular person since I am always talking about noises, and vibrations, etc. I'm not. I just get a lot of noises.

Anyway, this time I have a vibration at about 50 - 55miles/hr. I know its not the tires inteh front since I don't feel it in the wheel, and I have had DW on many occasions, and I am familiar with the sensation.

It seems to be driveline vibration. Its not a shimmy, just a general roughness that I feel. Here's a background:

It has only started this year, and I commuted a fair bit on the highway last year. I am now in a new home, and rarely go on the highway. This spring I put on new BFG MT 33x10.5's, and added a body lift and budget MML. I notice no extra vibs wehn around town or idling. I do feela ticking in my feet, but I am 99% sure this is an adjustment of the t-case linkage which I haven't performed yet ( has anyone else with a mml had to adjust the linkage? According the JKS I didn't have to)

I have a 2" B in the rear, and ACOS spacers in the front, lifted about 2"

After looking under the Jeep, it seems te rear driveshaft is almost perfectly in a straight line. The front however, where it comes out of the t-case is at a bit of an angle. Cold this be the cause.

Here's another wrench in the plan. I recently had a new front left axleshaft u-joint replaced,a dn a rear-end pinion seal replaced at the dealership.....could one of these repairs be the culprit??

Sorry to ask another techinical question, but I am hoping someone may have experieiced something similar. The problem I have is that I didn't travel the highway over 35miles/hour untial after all these mods were done, so I can't narrow it down.

Thanks!!

[n3cr0shark]

Yeah, I have the same thing/feeling. I wasted a lot of time on tire balance but the rough feeling is still there at the higher speeds. I think the MML/BL combo on the LJ (well some LJs) may be either overcorrecting the rear driveshaft angle or the LJ is more prone to feel a front driveshaft vibe.

I checked my angles after my lift and my rear angles were basically too perfect and its possible my pinion may be going to high under load. And my front pinion angle is off after the lift and I believe I need to get some Adj Control Arms. I'm going to play around with the lower control arms sometime this summer to see if I can dial it in any better.

[nfunlimited]

Thanks a lot. Its nice to know I'm not the only one experiencing this. How long have you had it? No ill effects?

You have the tummy tuck as well? I can live with the roughness as long as nothing is going to come apart on teh highway.

Thanks again

[RubiRedLJ]

I definitely had a vibration after doing my MM lift, BL, & TT.

The MORE MM's are rubber, BUT transmit more vibes than the OEM MM's. The extra vibes in my case, I assume is just the difference in the materials that Jeep uses and that MORE uses. When sitting idle, it's hard to see out of my side mirrors because they are vibrating and making it hard to see. Not so bad that it's at all an issue. However, the poly bushing MM's do transmit significantly more vibes than the OEM or MORE MM's. That is the reason I didn't go w/ a poly bushing MM lift.

When I first did the aforementioned mods, my exhaust was hitting the UCA mount on the front driverside. It started very quietly and then escalated quickly to really annoying. Trip to the muffler shop solved that.

Not really sure if any of that babble helps but, good luck anyway. Just for good measure, I'd re-torque everything or check it, and just double check my pinion angle which should be fine.

[n3cr0shark]

No TT here but netted around 3.25" with the springs alone. I had serious Tire balance issues with my DC's on Steelies which I've worked through (finally got some Centramatics which helped!). But I definitely have to fix my front pinion angle. If I pull it into where it's supposed to be, my Caster will be back in specs as well. I think the combo of bad caster and the bad pinion is my issue, but only time will tell when I finally fix it.

As for negative issues...well, I've got 5k on it since the lift and don't see anything negative 'yet'. If I don't take care of it, I expect I'll have negative issues like U Joints or seals eventually. But all I've seen thus far is slight seepage from the rear pinion (need a new seal) which is common and once I got the massive vibrations due to the tires under control, the seepage has even slowed. As it is, the U joints, hub bearings, and all 'look and feel' ok....but I'll go with the adage that any vibration is a bad thing...

I've lived through a Death Wobble and throwing a drive shaft at 70mph on my old Zuki when I was in college. I definitely do not want to go through that again, so I'm still on a mission......

[nfunlimited]

For me the idle vibrations are the same as stock since I used the JKS budget MMl. It seems to me to be driveline since I can notice a change from when teh clutch is in or out. However since it comes on at about 50, maybe it could be a poorly balanced tire. I changed so many things this year (tires, mml, bl, new seal for the rear pinion) that I am finding it hard to locate the vib.

How can I correct the front driveshaft angle?

[n3cr0shark]

New Control arms. I'm looking at adjustable lowers as I'm on the cheap side right now....but many recommend new fixed lowers and adjustable uppers.

[nfunlimited]

I guess a tummy tuck would help the front ds angle too since it will level the t-case, instead of having it tilted up on the front like it is now.

Anyone have any knowledge on that?