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-   -   MML help (http://www.wranglerforum.com/f282/mml-help-227053.html)

WVU Mountainman 03-12-2013 12:24 PM

MML help
 
Installed 2" springs and have driveline vibes even after dropping the TC skid 3/4". If I install a MML will this cure my vibe problem?i do not have a BL I hate that I had to lower the TC skid.

IslandTJ 03-12-2013 01:12 PM

You don't need a bodylift to install a MML, you will just have to adjust your fan shroud accordingly. Generally, with a short 2" lift - the MML will be enough to align your driveline sufficiently to rid vibes. If it were me, I would remove the transfer case drop and then install the MML. Test drive and if I had some vibes, drop the transfer case a washer at a time until the vibes disappeared.

Boobooo 03-12-2013 02:41 PM

just a small note: When you do your mml lift, replace one side at a time. Don't remove both body mounts at once or you could turn a 2 hour job into an 8 hour job... ask me how I know... good news is once you're able to line up the bolts and get them in, it's smooth sailing from there...

wwch99tj 03-12-2013 03:54 PM

Quote:

Originally Posted by Boobooo (Post 3493747)
just a small note: When you do your mml lift, replace one side at a time. Don't remove both body mounts at once or you could turn a 2 hour job into an 8 hour job... ask me how I know... good news is once you're able to line up the bolts and get them in, it's smooth sailing from there...

I see everyone posts don't do both sides at once. It took me 30-45 mins to put mine on doing both at once, I jacked the motor from the oil pan near the harmonic balancer. Didn't have any problems...

Patrick H 03-12-2013 04:10 PM

I know most people like to play a guessing game with drive line vibrations. Add a MML, add some washers under the skid to lower the transfer case. Take some washers back out, repeat, etc.
In my opinion it's easier and faster to just get under there with an angle finder and figure out what you need.
There are two major things that cause drive line vibrations in a stock type single cardan shaft.
First, there's actual u-joint angle. There are varying opinions on what is acceptable, but I personally like to try to keep the u-joint angle at 10 degrees or less. This is determined by measuring the angle of the drive shaft itself, and comparing that to the pinion shaft angle for the rear u-joint, and comparing it to the transfer case output shaft angle for the front u-joint.
Second, is matching the angle of the two u-joints. The way to determine this is to measure the angle of the transfer case output shaft, and measure the angle of the pinion shaft (relative to horizontal). These two angles should be within 1 degree of each other.
Measure these things, figure out what needs to be changed to achieve both, and be done with it. Your u-joints will thank you.

http://www.4xshaft.com/images/2joint_angle.gif

Boobooo 03-12-2013 04:10 PM

1 Attachment(s)
I wish I was that lucky... My motor must of twisted just right to prevent the two bolts to line up... I ended up having to undo the drivers side motor mount completely which was further complicated because I used blue locktight instead of red (thus the extended bolt came loose)... Once lined up, it went together quick... pic below shows how close it was to lining up, but no amount of lifting or lowering the motor could get it working until I started over... (this time with red locktight)
pic below shows how off tilt it was -

(now I try and follow instructions...)

wwch99tj 03-12-2013 04:47 PM

I hung mine from the through bolt and lined up the lower bolts...

Batjeep09 03-12-2013 05:11 PM

Ok so I'm asking for a buddy. Y'all are saying if you lift the jeep with a suspension lift, you have to lift the motor mounts?

Boobooo 03-12-2013 05:15 PM

I coupled a 1 inch body lift with a 1 inch mml so I wouldn't have to deal with modifying the fan shroud. Already had a OME 2.5 lift when I bought it.

Patrick H 03-12-2013 05:20 PM

Quote:

Originally Posted by Batjeep09 (Post 3494323)
Ok so I'm asking for a buddy. Y'all are saying if you lift the jeep with a suspension lift, you have to lift the motor mounts?

No. Usually motor mount lifts are installed with small suspension lifts to help alleviate drive shaft angles if a slip yoke eliminator and double cardan rear drive shaft are not installed. They do have other benefits/ uses, but I'd bet this is the most common. If drive shaft angles are OK, and/ or a SYE and double cardan shaft are installed, a MML isn't needed.
Or, as noted above, they can be installed with a body lift to keep the fan centered in the shroud, etc.

WVU Mountainman 03-12-2013 05:34 PM

After it was all said and done i dropped the TC 1" 48 grade 8 washes total. Still wobbles on take off. With the 2" lift I have what appears to be a steep rake rear to front. I purchased some .75" spacers for the front. In theory Will raising the front better my driveline angle and reduce driveline vibes?

Patrick H 03-12-2013 05:45 PM

Quote:

Originally Posted by WVU Mountainman (Post 3494416)
After it was all said and done i dropped the TC 1" 48 grade 8 washes total. Still wobbles on take off. With the 2" lift I have what appears to be a steep rake rear to front. I purchased some .75" spacers for the front. In theory Will raising the front better my driveline angle and reduce driveline vibes?

Absolutely not. If that were the case, your rear drive shaft angle would change when you drove up hill. You have to change the relation between the rear axle and the frame, or the engine/ transmission/ transfer case and the frame to change drive line angles.

Patrick H 03-12-2013 05:48 PM

If I were you, I'd start by actually measuring the angles on your rear drive line as I posted above so you know exactly what needs to change, and how much.
That said, a MML will help.

Pink_Percy 03-12-2013 05:50 PM

Quote:

Originally Posted by wwch99tj (Post 3494010)

I see everyone posts don't do both sides at once. It took me 30-45 mins to put mine on doing both at once, I jacked the motor from the oil pan near the harmonic balancer. Didn't have any problems...

I'm with you on this one. Took me 45 minutes to install a mml. So much easier at the same time.

ronb256 03-13-2013 06:07 AM

Quote:

Originally Posted by Patrick H (Post 3494454)
Absolutely not. If that were the case, your rear drive shaft angle would change when you drove up hill. You have to change the relation between the rear axle and the frame, or the engine/ transmission/ transfer case and the frame to change drive line angles.

The reason it own't work with the spacers is that you would only be changing the body to frame angle, not the engine or differential to frame angle. Good catch Patrick. I had to think about that for a moment, maybe because it is almost the end of night shift.

Patrick H 03-13-2013 08:42 AM

Quote:

Originally Posted by ronb256 (Post 3497131)
The reason it own't work with the spacers is that you would only be changing the body to frame angle, not the engine or differential to frame angle. Good catch Patrick. I had to think about that for a moment, maybe because it is almost the end of night shift.


Putting spring spacers on the front springs, or anywhere, does not change the way the body attaches to the frame.

WVU Mountainman 03-13-2013 08:43 AM

Then how does installing taller springs affect driveline angles?

Patrick H 03-13-2013 08:45 AM

Quote:

Originally Posted by WVU Mountainman (Post 3497427)
Then how does installing taller springs affect driveline angles?

By moving the axle away from the frame, or more to the point, moving the pinion shaft away from the transfer case output shaft.
But moving the front axle does not affect the rear axle.

WVU Mountainman 03-13-2013 12:34 PM

Gotcha. Thank you. I've been racking my brain on this. Mi driveshaft angle is 12 degrees looks good but still wobbles on take off. Here are some pictures

IslandTJ 03-13-2013 12:39 PM

It appears your pinion is too high, it needs to be parallel with the transfer case output shaft.

Would actually be spot on if you had a DC driveshaft ;)

WVU Mountainman 03-13-2013 12:47 PM

Do you think a MML will solve the problem?

Patrick H 03-13-2013 12:56 PM

Quote:

Originally Posted by WVU Mountainman
Do you think a MML will solve the problem?

Did you measure the output and pinion shafts?

WVU Mountainman 03-13-2013 01:12 PM

Best I could with my I phone app. TC output 11 degrees pinion angle 16. Keep in mid this is after dropping the TC skid 1".

IslandTJ 03-13-2013 01:19 PM

Quote:

Originally Posted by WVU Mountainman (Post 3498279)
Do you think a MML will solve the problem?

Hard to say with a 5 degree difference. However, if we were to pursue resolution starting with the least costly mod, a MML lift should be considered and if that doesn't work the pinion angle may be dialed down with adjustable control arms.

Best case fix would be the SYE route...

Patrick H 03-13-2013 01:23 PM

You won't get 5 degrees with a MML., but it'll get you closer. I welded in some offset plates in the rear upper control arm mounts on the axle to push the pinion sown a bit, and lengthened the lower control arms a bit. With a mml, I was able to match the pinion and transfer case shafts, and still keep thE rear diff. out of the fuel tank at full bump.

Patrick H 03-13-2013 01:29 PM

And yes, SYE is in my future, but I wanted my drive line angles to be correct in the mean time. I did have to end up leaving about 1/2" drop on the skid. It's the best I could do until either the money tree blooms or I quit feeding my family.

WVU Mountainman 03-13-2013 01:29 PM

Is this a normal issue with 2" lift? Will the springs settle at all? Will it hurt anything driving as is for a while?

Patrick H 03-13-2013 01:31 PM

I personally won't drive mine if the angles are far enough out to cause even the slightest detectable vibration.

WVU Mountainman 03-13-2013 01:40 PM

Will adding weight to the rear affect driveline angles?

WVU Mountainman 03-13-2013 01:41 PM

Also I did not install a rear trackbar relocation bracket. Will this affect driveline angles


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