View Full Version : Rearend Shudder
Have a 2012 K3500HD CC with about 4,000 miles. Experiencing a slight shudder or vibration from what feels like the differential when taking off from a dead stop. Fell it only when loaded, i.e. pulling my 32 ft 5th wheel. Occurs only on takeoff to about 5 MPH. Feel nothing when empty or not towing. Anyone else run into this? Is it a rearend problem or perhaps spring wrapup?
Long bed truck?
They've all been doing that for years it's just that some don't notice. Tipping the pinion angle down about 3° should help. Just be sure to use a high quality shim. I used a cast aluminum set and they crumbled.
Thanks, John. Yes, it's a long bed dually. All my previous ones were shortbeds.
More Power
10-31-2012, 12:20
Your dealer may help with a solution.
Like John said, a shim would likely help. What's happening is... while loaded and accelerating from a stop, an inequality in U-joint angles exists between a pair of U-joints somewhere in the rear driveline.
For a given length of driveline, the two U-joints need to operate at the same angle (there is some leeway) or shudder can be felt.
Jim
Try clamping the leaf springs forward of the axle. (old drag racers trick) John's right, the differential is rotating, changing the pinon angle.
JohnnyR,
I was concerned about the same shudder in my 2006, CC, 4x4, dually. The truck has 183k hard towing miles and has always had the (common) shudder. At 166k miles the driveshaft carrier bearing failed. When I replaced the bearing it improved a small amount but there is still a noticeable shudder when pulling out with a loaded trailer. This seems to be a common issue with the CC, LB trucks. I do recall some discussions of this issue here on the DP several years ago about GM fixing some trucks with a super long one piece driveshaft. I personally would prefer the standard one piece shaft. If you find a solution please post it. If you can't find a fix for the shudder I would drive it and not worry.
Good Luck
John
GM Customer Service
10-31-2012, 19:25
Have a 2012 K3500HD CC with about 4,000 miles. Experiencing a slight shudder or vibration from what feels like the differential when taking off from a dead stop. Fell it only when loaded, i.e. pulling my 32 ft 5th wheel. Occurs only on takeoff to about 5 MPH. Feel nothing when empty or not towing. Anyone else run into this? Is it a rearend problem or perhaps spring wrapup?
JohnnyR,
I agree with More Power, With you having very little miles on your truck and I would assume you are in Warranty. I would contact your GM Dealer Service Department. If you have any questions, comments or concerns please feel free to contact me.
Thank you,
Tina
GM Customer Service
Try clamping the leaf springs forward of the axle. (old drag racers trick) John's right, the differential is rotating, changing the pinon angle.
This would be the incorrect direction and would pull it worse. Rear would probably help this.
Your dealer may help with a solution.
Like John said, a shim would likely help. What's happening is... while loaded and accelerating from a stop, an inequality in U-joint angles exists between a pair of U-joints somewhere in the rear driveline.
For a given length of driveline, the two U-joints need to operate at the same angle (there is some leeway) or shudder can be felt.
Jim
What is happening is the angle at the rearmost joint goes to zero or even "flips" to the opposite direction.
I have not yet investigated mine, but in the past I have also used a couple/few 1/8" body shims under the transmission mount to decrease the angle on the front and mid joints.
This is something that the long bed trucks with 2 pc shafts have faced since 2001 and hasn't really been cured on the production lines.
I'm not so much a fan of amazon, but ended up buying there as I needed fast and reliable delivery. http://www.amazon.com/gp/product/B004JARX70/ref=oh_details_o02_s00_i00
Also do you have the annoying roar/buzz underhood at RPM above 2500RPM primarily towing?
John........I can only reference this: http://www.rm-indy.com/spring_clamps.htm. It worked for me.
Cars and low slung vehicles often have the trans output shaft at same or lower height than pinion so this could explain the reason for the clamps at the front.
In any event, the pinion is climbing and erasing what little angle there is if not crossing over as well. This needs to be prevented or minimized. Adding a shim adds angle so that it does not go away.
Spuddy98
11-05-2012, 09:43
First post for me. A buddy has this problem too. We may try to mount a camera to confirm the axle wind up.
On the clamping idea the old drag racer trick is correct. By clamping springs together - either in front or in back - you will increase the torsional rigidity if the leaf if that's the right way to put it. Essentially you stop the leaves from rubbing together making them stiffer. If clamping them changes the vibration then you have the problem. Back in the day we ran a 90/10 shock horizontally forward over the axle on our leaf sprung stock cars.
So, hopefully, I haven't offended anyone. So Kennedy, have you actually installed the wedges and found an improvement? It makes perfect sense that it is axle windup especially considering you are moving a 9000 pound truck off the line. Seen heavy trucks bounce like this but always thought it was a clutch issue.
Going back to JohnnyR's original post:
Often times adding support to the rear to keep it up helps with the shudder.
On my 2012 I added Air Lift bags as I normally do on my work trucks. This time I took my own advice and added the Air Lift Wireless air as well. Let me tell you first trip out I knew I made the right choice. Having the ability to add or remove air from the rear is awesome. We hit the road to Denver with my '02 on the trailer. As I recall I started with 35 psi in the bags. The expansion joints started to get the hopping thing going so I hit the up button twice (once to wake it up and again to express up 10 psi) and moved to 45 psi and the change was immediate. Years back I had in cab control in my '96 but it was manual and had dual gauges, tubes, abd a very inexpensive compressor. This new Wireless is first class and no penetrations through the firewall!
My 02 got an additional leaf when it was about new. Basically it's a 3500SRW without the slapper springs. It had the shudder so I added wedges and that took care of it. My 05 also had the shudder. I believe I did a little shimming under the trans mount, but never the wedges with this one. I just lived with it. My '12 does it now but I can get away from it somewhat with air in the bags. I do intend to look at the angles but they are VERY tough to measure accurately. Snap on is supposed to have a nice ujoint angle checker but I have not tried it personally. My guess is that when loaded the angle goes to near zero. Clamps will not do much eaither because the springs are already seated firmly on the lower leaf and under considerable compression.
One more thing: a set of Caltracs traction bars would definitely eliminate axle wrap but will also firm up the ride at the same time.
Spuddy98
11-06-2012, 08:28
If wedges is the way to go I will tell him. I think we can ge a good measurement with a cheap angle finder. The damper on the pinion is one good reference and the first driveshaft should be a reasonable 2nd reference. I will look at the transmission to find another. I'm sure Allison must have some point on the case that is parallel with the driveline.
My buddy claims he threw his angle finder on the pinion damper and found it to be uphill at 8 degrees! Don't really know if the ground was level but we don't live in w. VA. so it should be within a few degrees.
He's being real picky and wants his 07 with 110k miles to drive like new. I'm not so picky on my Ford with 225k miles but I think the worst problems I have are some original shocks and a worn steering gear. Loved the Holsteins on my last truck and plan to get them for this one when I can afford them. ( got to fix Daddy's princess fan clutch and ball joint first!)
Thanks for the reply Kennedy. If anyone else has advice on the wedges speak up!
It's so hard on these sites around the net to sift thru all the "suggestions" and to find someone who can say "I had that exact problem and this is how I fixed it and its been working well for X long!
It's really tough to get any TRUE surface to mrasure be it the Tcase or the rear damper as the damper is rubber mounted.
Loks to me like indicating off the Ujoint caps themselves is the best way.
I did a quick check and it sure seems to me like we have between 2° and 3° between the Tcase and shaft 1. This should be <1° so we start out on the wrong foot.
JohnnyR,
I agree with More Power, With you having very little miles on your truck and I would assume you are in Warranty. I would contact your GM Dealer Service Department. If you have any questions, comments or concerns please feel free to contact me.
Thank you,
Tina
GM Customer Service
Tina, one question is I may. I am having the same issue when towing. I only have 2800 miles on my truck. When I hooked the fifth wheel with a dry weight of 12k I got the same shudder. What should I tell the dealer to get them on the right track in correcting this? They, unfortunately, are not very bright.
Thanks,
Glenn
http://mygtcs.com/mustang/documents/ford/2-Chassis//205-00-Driveline%20System%20-%20General%20Information-General%20Procedures%20(Driveline%20Angle%20Measur ement)%2004-2010.pdf
Launch shudder
WOW! Thank you so much Kennedy! I will take that to them. Guessing I will have to take the 5th wheel too...lol
WOW! Thank you so much Kennedy! I will take that to them. Guessing I will have to take the 5th wheel too...lol
Run the RPM's up when accelerating and listen for a nasty roar/resonance under the hood. Kind of like a quadrajet with the air lid upside down and rubbing the underside of the hood. Maybe the dealer can do two projects same visit.
I had the launch shudder on my '99 1500 but only when towing my travel trailer. Took it to the dealer and he found a TSB which identified a new rear leaf spring to correct the problem. The difference was the addition of another bottom leaf and replacement of the rear spring hanger. Problem solved.......They might possibly have a TSB for the 2500's too.
GM Customer Service
11-06-2012, 16:46
Tina, one question is I may. I am having the same issue when towing. I only have 2800 miles on my truck. When I hooked the fifth wheel with a dry weight of 12k I got the same shudder. What should I tell the dealer to get them on the right track in correcting this? They, unfortunately, are not very bright.
Thanks,
Glenn
Glenn,
I would be happy to see if I can get some information for you. Would you please PM me your last name, address, phone, VIN and dealer your working with?
Thank you,
Tina
GM Customer Service
Glenn,
I would be happy to see if I can get some information for you. Would you please PM me your last name, address, phone, VIN and dealer your working with?
Thank you,
Tina
GM Customer Service
Feel kinda silly but can't figure out how.
Run the RPM's up when accelerating and listen for a nasty roar/resonance under the hood. Kind of like a quadrajet with the air lid upside down and rubbing the underside of the hood. Maybe the dealer can do two projects same visit.
Solved the buzzing with some zip ties!
Solved the buzzing with some zip ties!
I'm thinking I'll make GM fix this one.
GM Customer Service
11-07-2012, 14:12
Feel kinda silly but can't figure out how.
Justlkn,
I messaged you in your profile.
Tina
GM Customer Service
Spuddy98
11-08-2012, 17:29
Well, after showing these posts to my friend he attached a camera to the underside of his truck and after backing out of his driveway did several launches and stops. It showed a really strange buzz just as he stepped on the fuel. Maybe I can share the video if he will send it to me.
His next step was to shim the center support bearing. He tried it initially with two heavy hardened washers on each side with little effect. When I told him that someone here had done over an inch he thought he'd better try more. He used a thick nut that allowed just enough threads to safely clamp the support in place. This nearly eliminated the shudder and he plans to have a thicker shim made that will also support the rubber surrounding the bearing. He also is going to order the 4 degree steel shims from amazon. Thanks Kennedy! Now what is up with the General Motors customer service trying to hyjack this thread and go to private messages. We all deserve to k ow the solution. My friend, a second owner of an out of warranty truck with 110,000 miles on his '07 deserves an answer if there is one!
I have also encouraged him to replace the center support bearing - not because of the bearing but because of the rubber. He wants to spend 500 beans for a new driveshaft because he figures that with u-joints and bearing and labor to put them in his old shaft it will only really cost a couple hundred to get new tubes. He also was going to have the old shaft checked at a driveshaft shop. But that's another $60 and its an hour each way.
Keep the updates coming and I will try to get the video.
Spuddy98
11-08-2012, 17:56
Here is a small portion of the video he sent me.
File is too big so I guess it's got to go to youtube
http://www.youtube.com/watch?v=9oxhAvZy0GU
Watch the angle on the frontmost joint and try to keep near zero. As you move the bearing down too far you will likely gain a minor but constant vibration at this joint.
If you want to open another can of worms look at the front shaft angles. They are not opposite/cancelling like they should be. Shimming up the transmission helps on this regard. When I say shims I mean the old body shims with tabs kind of h shaped.
IMO shimming is a pretty touchy thing to do.
If you get it right when towing, what's it going to do when empty.
I had the same issue towing my 13.5K 5th wheel, I installed Firestone airbags to bring the height back up to the stock height when towing with about 60-80psi. NO MORE SHUTTER/SHIMMING. When empty I just drop the air pressure back down to 5psi.
A pretty simple fix with no guess work on shimming.
If you don't like Firestone there is always Airlift.
Bags help some, but it still does it on mine.
I know if I don't air them up enough I'll still have the shimmy.
When I air them up pretty close to the stock heigth when loaded with about 80 psi, no issues.
For me anyway.
Glenn,
I would be happy to see if I can get some information for you. Would you please PM me your last name, address, phone, VIN and dealer your working with?
Thank you,
Tina
GM Customer Service
I have tried several times to send you this info. It refuses to cooperate.
Went by dealer yesterday and discussed launch shudder with a service advisor who spoke with 2 of his techs. End result was they didn't know how to fix it and were apprehensive about shimming center carrier bearing as it might make it shudder empty instead of loaded. My concern is the impact over time. I have 12,500 miles on truck now, having just returned from a 4,000 mile roundtrip to CA pulling my heavy 5er, and it shuddered everytime from a compete stiop to about 10 mph. Anybody know why this doesn't happen to all 2 piece driveshaft long wheelbase GM trucks? OR perhaps like John K said previously, it does but not everyone notices. Would replacing the stock 2-piece driveshaft with another stock new one solve the shudder? My thinking being my existing yokes are just "out of tolerance" enough to add up at the appropriate angle and produce the launch shudder.
Sorry for the long post. Just a bit frustrated. Really like the truck otherwise.
More Power
03-15-2013, 12:23
I have tried several times to send you this info. It refuses to cooperate.
The PM system should be working for you. Let me know if you're still having trouble.
Jim
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