AAM driveline Center Support Bearing Insp

[GCroyle]

TDR Folks,

Q. What does your AAM Center Support Bearing (CSB) rubber suspension/bumpers look like?

2005 5.9L NV5600 QCSB over 200K on the clock.

I'm investigating a seat/rear body vibration that has possibly been a long time lurking problem but made it to the radar screen and is getting some attention. This AAM driveline has only been R&R for clutch work, all parts are as built. It will come out for a detailed U-joint insp but nothing obvious in the on vehicle evaluation but it could prove me wrong later. TBD.

Take at look at the two pics, one I'm showing the gap that can be seen at the bottom of the CSB rubber bumper to the bearing assy just by pushing up with both hands. It's right at 1/4". It appears that this CSB suspends the bearing from each corner of the frame and has travel bump stops at top, bottom and the sides. ?

The second pic shows my home shop diagnostic attempt. The red strips are rubber and are 1/8" thick and it didn't take much effort to slip them in at sides, top or bottom. This pic shows both at the bottom current test is one ea at top and bottom. Next up test drive for a bit to evaluate and make decision as to next step, parts etc. The jack is only supporting the shaft in the UP position, not much force at all.

I did find an informative AAM bill of materials for my driveline https://www.demandaam.com/technical...ials/ram-2-piece-driveshaft-bill-of-materials use your driveshaft part numbers and check for AAM assy and components that it uses.

I haven't had enough seat time on various roads to determine outcome to knock down or at least "touch" a possible source etc.

Gary

 

[jghflys]

You can see in the pictures that the rubber is cracking, shrinking, and dry rotting. I had a bad U joint also and replaced all 3 U joints at the same time, because it was apart.

 

[TFucili]

I'd agree with the cracking, I think you've got the goody out of that one, even if not the source of the issue.

 

[GCroyle]

jghflys,

I noticed the cracking too but it's not through and totally split from my insp as installed. Further insp when removed will tell a bit more. What would be a bit interesting is seeing a new AAM CSB for comparison. Does it suspend the bearing from the corners as I assume or?

Is your driveline also AAM, did you replace the CSB with the U-joints?

 

[GCroyle]

I'd agree with the cracking, I think you've got the goody out of that one, even if not the source of the issue.

Recently TDR mag included a write up about the John Kelly, Weber Auto vibration analyzer app. Wish I had it but not being a shop a bit on the wish list.

I do have a line on an old school mechanical vibration tool just waiting for my buddy to find it and ship it for me to try to determine "order" etc. Diagnostics will get their turn at bat before completely firing the parts cannon.

Yes, side effect of the main problem, shaft vibration and CSB is just allowing it to surface due to it's age?

Hopefully TBD.

 

[nibroc]

gonna cause me to go and inspect mine

 

[seafish]

If the it turns out to be the source of your vibration, you may want to consider eliminating the entire center bearing support structure and replace the entire driveshaft with a single peice aluminum driveshaft, either stock or upgraded.

While certainly you have gotten your "money's worth" out of the oem bearing/support, the single peice driveshaft upgrade certianly removed a failure point on my truck when I upgraded to it after the second CB rubber bushing failure in 125k. It also substantially lessend the trucks vibration, both on roll out and at some highway speeds.

 

[Tuesdak]

It also substantially lessend the trucks vibration, both on roll out

If you can't do a single piece and by the time you rebuild yours with a new center bearing the cost is the same...

Taking off loaded = launch shudder. Say you have a hopped up 6.5TD and a heavy trailer. Or doing a brake stand with eyes on the driveshaft. The Driveshaft will bounce up and down in the rubber support bearing. I dropped a poly support bearing on the driveshaft and eliminated the launch shudder, however, with 4.10's it had a vibration at high speed (above trailer towing speeds). This was after dropping $500 on balancing, straightening, and rebuilding the driveshaft. Some rigs can't get a 1 piece driveshaft for length reasons.

Some Dodge RAM owners have used one of these poly bearings making sure to make a plate for the top (as GM uses a crossmember to keep the rubber in.)

https://www.iedls.com/Online_Store/3/12

The rear leaf spring wrap being a part of this is another discussion.

 

[GCroyle]

Sorta wish I'd kept a logbook of when, where etc on the vibration concern.

One thing I am very conscious of smooth take off / smooth clutch engagement. This thing takes off SMOOTH empty or loaded and launching or backing up with the Airstream no issues.

Another challenge is repeatability of test conditions, same road conditions is one of the hard ones going back and forth etc.

I had it on the highway yesterday with one shim top, bottom, left and right and up to just below 70 or so, pretty good. 73+ and the shake kicked in. Tires are 1 yr old and I can take them in for balance and rotate and see if the weight position changes etc. Next will be to remove shim from top and double on the bottom and repeat route.

Research continues and more trials. Really hoping my buddy a former Chrysler field trainer can find his old what ever it was and send it to me.

And if you want to go deep on U-Joint operation, servicing and measuring here ya go part 1 of 7 videos about more than you asked for about them

Thanks for ideas and comments.

Gary

 

[Tuesdak]

Your shims are making this a poly center bearing. High speed will make a vibration in the driveshaft show up with a solid center bearing like you are making. A good center bearing may solve your problem esp. if you give the shaft "the works" when it's replaced.

In the seat is from the rear: tires, driveshaft, brake drums/rotors ... something out of balance, alignment, or bad bearing. Don't ask about the warped drum that took forever to find. One nice looking used truck in the dealer shop I was considering trading for had a bent axle. Suddenly, after overhearing the mechanic tell the shop manager, I didn't want to know why... I have had 4 tires separating on a trailer be an in the seat and in the mirror vibration.

 

[GCroyle]

Your shims are making this a poly center bearing. High speed will make a vibration in the driveshaft show up with a solid center bearing like you are making. A good center bearing may solve your problem esp. if you give the shaft "the works" when it's replaced.

Tuesdak,

You just might be on to something here. I have heard of poly engine and trans mounts didn't know they exist for a CSB. Don't know if they exist for our applications, don't want one.

TDR

A quick visual inspection can not replace a THOUROUGH visual inspection.

A much closer look at the way this bearing is presented in this CSB leads me to these observations. The bearing is suspended diagonally at the corners and has a stop or travel limiting perimeter that has an air gap. Now take a look at this pic of the pass side top suspension support, cracks, noticable large gap at top, small gap as it's allowing the bearing to hang down and it was resting on the bottom stop.

Yes, when this shaft comes down it's getting "the works" and my likely supplier will be AAM joints, CSB, bellows and clamp from Dennys Driveline. Here's the 1485 AAM joint.
https://www.dennysdriveshaft.com/p3...al_joint_1485_series_fits_dodge_aam_rear.html

And I sent in for my Viewed Them All certificate from John Kelly for his ~6 hr U-Joint video series. Some neat stuff including the history of this part.

Gary

 

[seafish]

Yup, that is EXACTLY what mine looked like,

IMO, too little rubber foir too much torque ... LOL !!!

 

[Tuesdak]

I would second @seafish advice to drop a one piece driveshaft in there. The cost of rebuilding yours is high enough to make it worth looking at it. I recall only the 2WD version of the NV5600 was too long of a shaft to do this with.

 

[GCroyle]

seafish, Tuesdak,

I have not researched a 1 pc replacement for a Dodge replacement part number. Not sure if one exists. My truck is a 2005 5.9L NV5600 2WD, QCSB. Got a part number? Per AAM data the shaft is a 52105656AG shaft length C-C U-Joints balanced is 71.162" that's AAM terms for length.

At Denny's Driveline for AAM parts, 1485 joints are $38 ea, 40021334 CSB is $47, boot kit 40021327 $14. About $190 in parts plus tax and shipping.

Thanks for the ideas and comments.

Gary

 

[cerberusiam]

71" is well within the limits of a 1 piece 5" aluminum DS if so desired. Beyond 84" is where the problems begin according to DL Specialists. If you already have vibes you may want to consider deleting the flange drive also as it is known source of problems.

Some of the racers sourced a center support that was more along the lines of a pillow block than the OE, much more rubber and a lot more solid mount. It held up racing and they claimed no extra NVH changes so it is possible to retrofit a better support.

 

[GCroyle]

Folks,

Looks like for right now this project gets back burner status as I have one more towing job for it early Dec and then I can pull it, bench detail insp and make a decision. I'll double check with my buddy about the old school vibration tool see if he can get it and check first.

Thanks for the comments and ideas. This is a component with a lot of I didn't know that stuff about it and John Kelly's videos go real deep into those details.

Gary

 

[GCroyle]

TDR,

It's raining and I'm pooped from doing battle as a DIY'er vs. AAM 2 pc drive shaft yada yada and at least this is not political or pandemic stuff.

This starts as a seat vibration and details above. I bet you thought another talk about it do nothing thread. I wish.

Ordered AAM parts from Denny's Driveshaft in NY https://www.dennysdriveshaft.com/ good shipping, you might have to get dirty to figure out what you need cause data is a bit funky IMHO. Anyway time for update.

Took most of the day to remove the three joints and learn how the heck is the best/least painful/non bloody way to do it. Rented a ball joint u joint tool set. Calling it a u joint tool is a big marketing ploy. None of the receiving cups matched or were usable with a 1.375" bearing cup. Nope.

OK now what? Make a cup! So I ran right over to my non existent steel parts supply which is next to my non existent lathe. Drat nothing there.

Ah ha! Use a 1 3/8" socket as a receiving cup! Trip #2 back to ORL.

Spent the next 40 min cutting the socket BY HAND and grinding it down to a potentially usable length, see proof in pic.

Now the alligator rasslin starts with those STEEL RUSTY AAM parts and my home made u joint press. I'll spare you some details just look at the pics.

Boy I wish I had a farm shop in my back yard to go to and get 'er done, no such luck. Just my garage and good intentions.

The CSB needs a bearing puller AFAIK and might have to make a trip to HF and grab a hope it works version. The rubber was holding the bearing by just good will not like the new CSB has a hold on it.

Each cross showed little bit of wear on one race each all still had grease in them, all flexed one had a small bind in it.

Bandaid count, ZERO.

Darn glad this was not my career.

Gary

 

[Tuesdak]

So you see why I just drop these off at a drive shaft shop and say "Shut up and take my money!" They come back with new u-joints, new center bearing, straight, and re-balanced.

FWIW it's the 2WD Long Bed that it too long for a 1 piece driveshafts.

Otherwise I would have just replaced the rubber and called it a day. Those U-Joints had plenty of life left in em!

The center bearing failing is the only reason I would rebuild a driveshaft. (They have a habit of failing due to monsoon flooding and getting water in em in flooded washes.) When they look like this then it's time. (Original 1993 with 180K on it.)

Or sound like this. Ok it was way louder on the road at speed and the radio couldn't cover it up...

 

[GCroyle]

Tuesdak,

I can see a case for that approach and this ain't over.

Cleanup starts in a bit then assy begins.

Gary

 

[JR]

Imagine how fun those would be if you still lived in the rust belt Gary.
I cut the cross sections out with a grinder and a 6" deli wheel so I only have to worry about pressing one cup at a time. Otherwise the risk of bending the ears is uncomfortably high.