nriver

For those following along at home, I ended up with Launch Shudder. I was thinking this is related to the 37s, the newest modification. I did get some shudder with the 35s, but it went away. It went away around 20 or so. But was a pain in the seat. The vibrations started making me think many other things were wrong; Bushings, U-Joints, alignment, and just started adding up the numbers and was thinking $2000

So I did a bunch of research on launch shudder on the web. I decided to try shimming the center bearing. Seems do help, but I just used some washers to see if it would fix the problem. Nope. Started thinking again about lots of money.

More research.

I found this part from Dodge, 5135709AA, it s a 1” center bearing spacer and bolts for about 70 or so. Then I thought if they use a 1” for stock trucks with this problem, my 5” taller tires could use more than a 1/4” space. I also started reading in the service manual and found this text.

ADJUSTMENTS CENTER BEARING
Launch shudder is a vibration that occurs at first acceleration from a stop. Shudder vibration usually peaks at the engines highest torque output. Shudder is a symptom associated with vehicles using a two piece propeller shaft. To decrease shudder, lower the center bearing in 1/8 inch increments. Use shim stock or fabricated plates. Plate stock must be used to maintain compression of the rubber insulator around the bearing. Do not use washers. Replace the original bolts with the appropriate increased length bolts.

HMMM, I thought. Why don’t I just put in a 1” spacer and some grade 8 bolts.

Then I went to the store and only found 1.5” stock. Hmmm, well 5” of tires, 1.5 should be fine.

Long story short, put the spacer in, Launch Shudder gone. Woo Hoo.

I may revisit the spacer with some larger stock, but for now. Shudder is gone.

thorbuilt

hey nriver can you post a pic of that center berring mod you did? I am having the same thing with my 35's i am hoping it will go away after 20mph...... I also was wondering if you could tell me where you got the powdercoat done as i want to do my boat trailer wheels i think it looks awsume, but i am not willing to do my mkw 19's just yet they still bling

thanks for any help you can give and for sharing your ride!

nriver

powdercoating at advanced powdercoating in portland. Johnson creek area. While I loke the look of the powder coating, i would do it differently next time. think I posted that earlier.

As for teh bearing mod, I will be back under the truck soon when i get my new rear springs in. I will get a pic then, unless I feel like laying under the truck. I sure need to get a creeper.

In general on the bearing spacer. I just picked up two sets of 3" 3/8 Grade 8 bolts nuts and washers. Then just take the two existing bolts out, support the driveline with a jack or something. Then put the spacer between the carrier bearing and the mount.

You prob dont need the 1.5" spacer that I used, it would depend on if you have going with your rear springs. My rear springs are basically stock with the overload springs replaced with mini packs.

thorbuilt

thanks Nriver.......

cquestad

The method to calculate the amount of center carrier drop is real easy...

Using similar triangles...or since the two portions of the drive shaft are almost the same length, drop the carrier 1/2 of the total SUSPENSION lift!

It has nothing to do with tire size...just the relationship of the axle to the frame. I droped mine 1-3/4" to compensate for my 3.5" of rear lift...and never have had launch studder.

I plan on fabricating a single 3rd member mounted axle wrap bar in the future to further releave stress from the driveline...and still maintain proper 4x4 manners.

nriver

Interesting, I do not have any rear spring lift.
I would think as the tires increase in size, they would change where the axle is in relation to the frame.

but at the end of the day, this worked for me.

ptgarcia

It's the axle that locates the tire, not the tire that locates the axle. Make sense?

cquestad

The mini-pac does not add height? It is possible that it could have been wrong from the factory.

nriver

I did not have any problems with Launch Shudder until I put the 37s on.

cquestad

It would definitley amplify the problem...but not cause it.

ptgarcia

You're probably getting a little axle wrap with that size tire. A well designed set of traction bars with take care of that.

nriver

Ill have the new springs soon.

I have also not seen a good set of 3rd Gen traction bars yet. Any Ideas?

ptgarcia

Maybe Don Thuren?

When I had my Titan I was lucky enough to hook up with a Titan specialist; much like Thuren, Lorenz and Carli; who lived in my backyard. I'd drive to his house and he'd do the work in his driveway. Once he even come to my office and installed a set of shocks! When enough people show interest he'd fab up what we wanted. Maybe Don will do the same?

Thuren's not too far from me, a little more than a 2 hour drive. I need to see him so he can take some measurements if I want to put those King Shocks on my truck. I actually have an opportunity to be in the area in a couple weeks, but it sounds like he'll be moving his shop at that time . I wonder if he'd be interested in fabing up some traction bars?

cquestad

Ya...I will have a sweet set when ever I can get out into the shop. I have the bushings and eyes right in front of me. Going to make it a single point above the 3rd memeber so it does not hang down or limit suspension travel.

ptgarcia

One thing I've learned over the years with track bars is that bushings at the forward mount can be problematic. I suggest an adjustable heim at that end, especially if you'll be doing any offroading in the "twisties", as I call it. Heims will allow the axle to articulate without binding. I've seen bushings take a beating and mounts actually fail on some trucks.