ok..... so thank you for trying to help, but, all that you have mentioned has already been gone over and dismissed.

couldn't BE any clearer, thankyou. i am supposed to get it on thur.

i sure hope it works cause i am not towing my trailer this way on memorial day!

 

I don't see how a leaf spring could be the problem. If it’s broken it wouldn't support the weight of the truck and one side would sag. IMO, the leaf springs are fine or you'd know.

Again...check the angles. The centerline of the tranny output shaft and rear axle pinion NEED TO BE PARALLEL TO EACH OTHER!!! When this is done, then check the center bearing support. Shim this support such that both drive shafts are PARALLEL to each other with a full tank of diesel and someone in the truck (or whatever loads you carry the majority of the time). Once this is setup you'd have what is basically a 1 piece drive shaft (accept for the play created by the center bearing and u-joint). This is what DC tries to do from the factory, but can't. Only problem is with the 2 pc shaft design. It stinks as it is effected by loading of the truck. Other option is to have the front shaft parallel to the tranny centerline and rear shaft doing the flexing, but the angles would be too severe.

Now - when you load the truck down the rear section of the driveshaft would be higher than the front creating an angle between the two. This will cause the shaft to want to bind as the front and rear accel and decel at different speeds as it rotates - thus causing the knocking noise and vibration. A 1 pc shaft won't allow this binding as there is no center u-joint / bearing. In addition a 1 pc shaft is a simple design in that the acceleration and deceleration is cancelled out on both tranny and axle joint … which equals no binding. BUT – the centerlines must be parallel.

I went thru all this crap. And if the newer trucks have a 1 piece shaft --- what does that tell you guys???? You guys do what you want but going to a one piece is the answer, IMO. HOWEVER - YOU NEED TO MAKE SURE THE TRANNY AND PINION centerlines ARE PARALLEL or you'll never get either setup working right - 1 piece or 2 pc driveshaft.

How are you guys measuring the pinion angle? I hope you guys aren't going off the axle housing.

Good luck....I've been in your shoes and it is VERY FRUSTRATING when the dealer is of no help and you need to fix stuff like this on our own. If I sound heated it's because I am! Evertime I hear about these driveshaft issues my blood boils....as I've spent many hours trying to work with the dealer to no avail. I was sick of hearing, 'the truck is working as designed'. Yes...but the design sucks!!!! Anyways, I needed to do this on my own, and on a $47k truck that was difficult to swallow.

 

Good luck guys!

It's obvious that you don't appreciate my kindness and attempts to help, and I won't be a whipping post for YOUR frustrations with YOUR truck.

 

I just re-read the posts.....and agree a defective part is the FIRST thing you need to rule out. Not doing that is just a big as that will certainly cause the shaft to bind and vibrate especially with all the play a rubber carrier bearing can give. But this should have been caught when you took the drive shaft down when checking output/pinion shaft angles.

 

Guys,

I will try to address a couple of points you don't seem to get.

1. IT IS DEPENDENT on driveline angles. I did get it to stop loaded but at the cost of a very steep pinion angle, that had a very severe unloaded shudder, and also a de-accelaeration shudder. This has already been mentioned.


2. Tranfer case and pinion angles are parelell. I've also tryed different combinations, and as stated above, nothing helps both loaded and unloaded. Unloaded is fixed with a shim at the center bearing, but its still severe loaded.

3. My theory about the leaf springs is that they are too weak to hold the pinion angle constant. My neighbor witnessed this when I had the truck loaded, and I was idling ahead as he looked at the rear diff. so I could stop in the right spot to check pinion angle. Said the pinoin was torquing up and down a couple degrees, and this was just idling ahead.

4. I use a modified choke angle gage I built myself to check angles. Works pretty good. I check the angles at the yolk on the flat "end" of the u-joint.


To all those who are trying to help, I truly appreciate it.

XLR8R-for someone who talks a good game, you really haven't contributed anything earth shattering.

 

when did I EVER use you as a whipping post?

 

Exactly! You can tune it to 1 angle but change the angle and you get a shutter. This is the nature of the design (2 pc shaft). Nothing you can do about it – unless you keep the first shaft parallel to the transfer case output shaft, which is impossible as the 2nd/rear shaft would be at a very severe u-joint angle (probably would bind and wouln’t even rotate).

When you say unloaded is fixed with a shim, does this mean the vibration goes away unloaded but comes back when loaded? Sorry if I don’t understand…just trying to get it straight.


I don’t think a degree or two would effect it that much. Set the pinion angle in the middle (under no load) so it may transition between +1 under load to -1 when coasting, or there abouts.

Try this --- have someone sit in the bed of the truck and watch the axle by viewing it between the bed and the cab. I did this and you could see how much the axle moves from one side to the other inside the carrier bushing between under power and while coasting.

Good luck!

 

The shudder is easy to get rid of unloaded. 1/2" shim at the center bearing did the trick. I decided to lower the back end by removing the spacer blocks in the spring pack instead. Ended up with the same result.

It is loaded that is the problem.

I still think the leaf springs are letting the pinion angle change more than 1-2 degrees. That was only idling, I think it would be worse when applying more torque to it.

The shudder went away loaded when I put about 6 degrees pinion angle (pointing down) into the driveline. This may just be compensation for the leaf springs allowing the pinion to torque upwards 5-6 degress when under power. But I couldn't leave it that way, because the unloaded shudder was so bad, and also created a shudder when applying the brakes.

 

well got it and installed it in about 20 min start to finish, you need a 15 mill socket and wrench to do the job and a bit of thread locker(blue) oh and 450 bucks..... but ABSOLUTELY NO LAUNCH SHUTTER.

I will take it on the free way a little later tonight and double check everything is ok but i'm sure it is. the reveal on the input shaft was the same as stock and the yolk bolts lined right up, and hell it weighs 40 pounds LESS!!!

you do have to remove the carrier bearing bracket, just four 15 mill bolts and nuts........done deal


ha ha ha to all you ne-sayers!!!!

oh and THE most important part.... the part number(how much do you love me)

52123162AA WC

list is 549.00 so talk em down to 450!!!!

 

Thanks for the update.

Once you unbolt the center bearing bracket, is there any kind of clearance issue?

Talked to my SM the other day to see if DC had a legit reason why not to change to the one piece. Haven't heard back yet.

Might just have to choke it and buy one myself.

 

none plenty of room

 

I only have experience with a custom 1 piece shaft so not sure if the 1 piece replacement you did will hold up - time will tell. My gut tells me you'll be fine!!! The point though is a single 1 piece shaft is the solution just as I've been posting all over the place. People who try to shim and try to get that 2-piece shaft to work are just 'SPINNING THEIR WHEELS'!

Happy the replacement part worked for you!!!! Good Luck!!!

 

"spinning your wheels" Ya thats certainly true in my case. Have to start "puttin the screws to DC". Maybe they will cough one up for me.

 

well $h!! it better its the one that comes stock on all the 08's

 

Yes, but DC designed it. They also designed th 2 pc shaft so.....like I said - TIME WILL TELL!

Sure it will be fine though......