Launch Shudder and Vibration

[MChilds]

Shudder/VIbration

Steve; thanks for the info. I can’t remember what vehicle it was, but I once had one that would vibrate harmonically and a driveshaft damper fixed it.



This problem is a shudder that you would think would be the worst out of round tire you ever felt except it shudders side-to-side and believe me, anyone would notice. What has continued to stump me is that when the truck is unloaded, the rear driveshaft angles down to the rear end but when it is loaded, it’s pretty much level. Either way, it shudders and vibrates. I installed air bags to keep the rear from going down as much, even adding enough air to keep the truck at unloaded ride height with the trailer but that didn’t help either.



There is a TSB that says this problem can exist when the carrier bearing moves below the rear axle pinion when the truck is loaded and to put on a one-piece driveshaft. Unfortunately, it doesn’t apply to my exact truck. One other thing that’s weird is that it takes about 20-minutes of driving for the problem to really get bad.

 

[MidwestMotorman]

Doh, I forgot that you had rear discs. Problems that get worse after warming- tires, ujoints, carrier bearings, hub bearings. Are the slip yokes properly lubed so they can slide? Maybe I would rock the truck back and forth in gear to check rear bushing flex. Is there a chance that one side of the rear end is not square on the springs?

Maybe a posi problem, too tight of clutch pack or lack of posi lube? Have you tried spinning both sets of tires on gravel or dirt? If you had a broken axle or something wrong in the carrier, you will feel funny pull or pulse of power to one side. If power is not being equally applied to each axle, you will end up with a wiggle. I have found out that I will get a vibration from my posi unit if there is over a 1psi variance in tire pressure from side to side (one side sitting in the sun will increase tire pressure around 2 psi).

Maybe I am getting too far off track. My dad's 93 3500 always had a vibration, side to side and very annoying at 55mph, that tire balancing/new tires never fixed. When I did the first brake job on the rears, I found that the right rear hub had 1/4" play, in and out! And it never had been touched since the factory. I corrected that, and no more wiggle.

 

[Devildog]

I had a shudder a launch, the dealer poured a conditioner in my rear LSD which helped. I also had to lower my carrier bearing block 1" which helped tremendously ( I have a 4" suspension lift ).

Have you checked into the rear differential?

 

[MChilds]

The drive shaft has been removed, balanced, slip-joints lubed and a questionable u-joint replaced by a reputable drive train shop. Also thinking it may be rear axle related, I changed the rear axle fluid and added Mopar fluid, test drove the truck and then added the conditioner. I changed it again and this time added Amsoil 2000 synthetic, drove the truck and then added conditioner. No luck. I’ve shimmed the drive shaft down and it seems to change things but never gets rid of the problem. I’ve driven the truck with the outer dual tires removed and checked and double checked tire pressures (I remember reading the tire pressure post some time ago). I’ve slipped the tires on takeoff in the dirt and made a series of tight turns listening and trying to feel a rear axle posi unit problem and it seems to work perfectly. I’ve shimmed the axle under the springs trying to change the angle and that made things worse, either way I tried.



The rear axle alignment is an interesting suggestion not being square with the springs. It does sit on the through pins and there has never been any abnormal tire wear like cupping that might indicate a problem (at 20,000 miles-this is a 2001. 5) and the truck goes straight down the road so I really never considered that. But I will now.



Also, I switched tires with a buddy’s exact truck to absolutely eliminate tire problems. He doesn’t have the shudder, his truck is exactly like mine and he pulls a heavier trailer than I do. I need to double check to see if he has a posi rear; if not, we may be on to something.



Thanks.



PS: The folks at DC need to read these posts. If they did, they could stop saying that this is the first time they ever heard of this problem. Boy, am I sick of hearing that.

 

[BIGMAN73]

I too had the same problem as you. Though not as dramatic. It would shudder on take off and produce a rythmic humm between 50 and 70 increasing on acceleration. They found that my rear u joints was bad and my bearings in the rear end were bad. If you have balanced the drive shaft i would asumme they checked the carrier bearing and u joints. But it can not nurt to check them again. If they are fine there might by somthing in the rear end not working right. Do you have 4x4 is so leave rear drive shaft off and drive it for a short distance and see if the problem re occurs if not you have just narrowed it down to the rear end.

 

[MChilds]

Bigman; I’d be real happy with just a rhythmic hum.



After receiving all the helpful suggestions on these posts and doing some more checking, I’ve pretty much narrowed it down to a bad rear axle/posi, the driveshaft, or both. I think with all the shimming and testing I’ve done on my own without results, it has to be a defective component or components and not just a simple adjustment or worn part.



Since I’m not willing to purchase the parts to do a swap & try I’m looking for DC to help with that. So far, they’ve refused but I’m still trying. I don’t know if you’ve read all the posts on this subject, but DC’s total involvement in this has been to suggest arbitration; they won’t dispatch or even give me the name of the factory rep. The truck is less than a year old and still within warranty.



BTW, even though mine is 2WD, I’m going to store the suggestion about removing the rear drive shaft to eliminate or confirm a bad rear axle in my ‘databank’ for future troubleshooting. Thanks.

 

[Lsfarm]

Check this:

MChilds, I just crawled out from under my 4x4 to check, and maybe this is so simple that even the driveshaft expert missed it.



On my truck the rear shaft has the female part of the sliding spline at the front and a simple rear ujoint at the diff.



The ujoint 'ears' on the driveshaft are in line, so the ujoints are inline or equal to each other. Or zero degrees to each other. The other option that may look normal would be for the 'ears' to be at 90 degrees to each other. This would be 'out of phase [I think this is what it is called]



However the front shorter shaft between the trans and the carrier bearing, [this shaft has the male part of the sliding splines] the ujoint at the front at the transmission output shaft has the ujoint 90 degrees from the ujoints on the rear shaft.



It may be that the rear shaft is welded with the joints not inline, at some random number of degrees to each other, not at zero degrees.



Also the front shaft may not be at 90 degrees to the rear shaft, it may be one or many splines off from the correct placement.



Just an additional thought, wouldn't it be great if it was such a simple thing??



Hope it is , greg L

 

[MChilds]

Greg,

OK, you may be on to something. I just got out from under my truck and both my shafts are in-line or ears to ears. If I understand the way yours are configured, your rear shaft is like that but the front shaft’s ears are rotated 90 degrees making my front shaft configuration different. The driveshaft shop did assure me my shaft wasn’t out of phase but being different than yours is certainly suspicious.



I don’t know if I mentioned this before, but Longhorn Dodge did do a STAR check (before they would let me bring the truck in) and the report showed that DC is aware of this problem and listed a number of possible fixes including an incorrect center support bearing and other drive shaft problems. Unfortunately, when I took the truck in, they refused to work on it or test-drive it with or without the trailer because it has a Pac Brake. Prior to that, West Loop Dodge refused to work on the truck citing an overweight trailer. (It’s not)



That’s my two choices in town so I’m now waiting for arbitration and while I wait, I’m afraid to do anything else that they could use against me. However, based on what you just told me, I would try a completely different driveshaft if I could find one. This is the first evidence that my truck (or drive shaft that is) may be assembled incorrectly or at least differently from one that doesn’t shudder.



Thanks.

 

[MidwestMotorman]

phase

It is my understanding that in phase is everything in line. On trucks, the grease zerks (when present) were all supposed to be in line.



Here is how they supposedly should be. The output yoke on the transfer case or transmission is 90* off of the rear end input yoke. The forward part ears (of big tube) of upper shaft is in line with the upper part ears (rearward of hanger bearing) of the lower shaft. The lower shaft ears of the rear rearward shaft are in line with the output yoke of trans or transfer case.



Clear as mud???

 

[fj40charles]

Sorry to hear about this problem. Truck vibrations really do suck. I know you went through and checked out the driveshaft for proper balancing and phasing. The only real way I would know for sure if it is the driveshaft causing the problem is to find a friend who has the same driveshaft and swap it out. I know this is a PITA, but it would be a real easy way to eliminate the cause.



Might want to check out this web site. Tom Wood's custom driveshaft. Very informative and helpful. Tom Wood used to run Six States (drive shaft shop) and now has his own place. He can custom build you anything. I run a custom CV driveshaft on my Toyota FJ40 this is only 18" long.



http://www.4xshaft.com/



I would try Manual Dodge in Richardson, TX. Please ask for Gene May, the service mgr. His number is 972-234-3444 or metro 972-949-2552. He was real helpful when I had a sqeaking sound under the the dash and it ended up being a problem with a pin switch being set up too high when I had a car alarm installed. It took them about 4 days to finally track down the noise.



Hope this helps. .



Charles

 

[MChilds]

Nathan



I crawled up under the truck again last night and I guess my shaft is OK. At least in the out-of-phase regard. When you look at it, the way it is put together is the only way it can be put together and actually work. Now, DC could have welded the shaft together out of phase lets say at 80-85 degrees instead of an exact 90 degrees but I don’t know a way to check that. I'm sure the best way to eliminate the drive shaft as the problem is to take fj40charles advice and replace the entire drive shaft with a known good one. If I just knew someone with a known good one. Thanks.



fj40charles



Thanks for the advice. I’ve looked at the site and I’m going to call Gene May.

 

[MidwestMotorman]

I think the only spot that one can mess up phase, is at the center slip yoke where the rear shaft slides over the forward one. You can get off a spline or two I believe, and maybe someone could have put it 90* off. I do not know if there is a double-wide spline to prevent a screw-up.

 

[MChilds]

Nathan

Funny, now that I’ve posted my launch/shudder and highway speed shudder information on the TDR, I’ve found out that a lot of these trucks can’t be fixed. I got a call this morning from a guy in North Carolina who doesn’t belong to TDR but was surfing the posts who has a 2001 3500 4WD and his dealer has replaced the drive shaft, rear axle assembly, transmission, cross members, etc. , all without success. Now there’s a dealer who cares. (Asheville Dodge) Unfortunately, they haven’t been able to fix what seems to be a random unfixable problem.



Looks like some can be shimmed and fixed and some can’t be fixed no matter what. I think mine may fall into the latter category and the two dealers from hell here in Fort Worth know it and don’t want to waste their time trying to fix it. Remember, dealers don’t get paid for troubleshooting. DC doesn’t want to tell the truth afraid of a major recall or being inundated with unhappy customers demanding a fix or new truck, like me. They would rather deny it and just deal with those that are persistent in an effort to keep the secret and save money.



Now, looking at my drive shaft, if there were a spline off I think that would be noticeable in that one ear would be closer to the u-joint on one side compared to the other. I was thinking that maybe the drive shaft was welded together slightly off which wouldn’t be noticeable causing the problem. Now after talking with the NC guy this morning, I’m beginning to think that I may have one of those trucks that can’t be fixed. Remember, a friend of mine has the exact truck and his doesn’t launch shudder or shudder/vibrate at highway speed.



Finally, in speaking with an un-named source at a Dodge dealership, he claimed that it was his opinion that some of the frames may be racked or twisted and on the ones he can’t fix, he found a ½ to 1” difference between the spindle to rear axle measurement between the left and right side of the truck. I measured mine and guess what, almost an inch difference. Could it be?

 

[Un-Hemi]

MChilds, what's the 'spindle'? I think you may be on to something here, as the driveshaft can be out of alignment horizontally also. BTW, my truck has a subtle 'hum/buzz' at about 55mph. I've had driveshaft/universal problems on nearly every Mopar I've owned!

 

[MChilds]

Tommy

I took my measurements from the center of the rear axle to the center of the front axle (or spindle) with the front wheels straight. Normally, you would see a slightly longer measurement on the right side due to some increased caster (positive caster to account for road pitch so the truck doesn’t pull to the right) but on my truck, the long measurement is on the left side.



When I bought the truck, it had what I considered a hard pull to the right and the selling dealer had to increase the positive caster on the right side to get the truck to go straight. They claimed that they never had to do that before but I passed that off as sales talk. Now I’m beginning to believe that there is something wrong with the frame alignment and may be the cause of the shudder at highway speed. BTW, mine is not a hum or buzz, it’s a pronounced side-to-side shudder that shakes the seat of your pants. Just miserable and unlike a tire that is relatively easy to isolate between the front or rear, this shudder shakes the whole truck.



Interestingly, my brother just bought a new 2500 Diesel 4 X 4 and his was one of the trucks they pull off the line and do a thorough check. He was allowed to view (at the dealer) what it is they do at the factory prior to releasing the truck for sale and there are a number of frame alignment checks. His passed and it’s slick without vibrations, hums, buzzes or shudders. I’ll bet there is a problem on the factory frame line and some of the trucks get through with a racked or twisted frame; no wonder the dealer doesn’t want to work on it. They probably know about the defect.

 

[MidwestMotorman]

MChilds---One of the members here already had this problem diagnosed. One of his bushing holes in the frame had been an inch off (a 4wd). I do not know how he came out, as the dealer found it and admitted to it being off. His father rode behind his truck in another vehicle and saw it going sideways down the road. He had a bad pull too.



There should be no more than 3mm variance from side to side. That is the acceptable tolerance in the collision industry. A vehicle will always pull toward the side with the shorter wheelbase. That much positive caster can cause a wobble. Fixed one problem and caused another...



There was also another post with a fellow whose bushings had egged out the holes in the front end. This will cause the tilted front too.



Sounds like DC will get you a new truck if that is the case. Maybe the arm mounts were placed off on the frame? You do have the regular suspension and not the straight axle front right? DC would just buy the truck back and resell it marked as "Dealer buyback" with "Alignment problems/vibration". If it was me, I would hack it apart instead of reselling, or make one heck of go-kart.

 

[CaptainEric]

My old '95 Reg Cab long bed 2500 had a launch problem, especially when loaded. D/C Service bullitens 030296 dated May '96 and 030496 dated Aug '96 addressed this problem.



According to D/C, the problem comes from the drive angle thru the constant velocity universal joint being to straight. These U-joints do not like to run in a straight line. There is a designed in 3 degree angle. As you load the truck, the body drops, thereby straightening out the driveline. The fix to my '95 was to replace the 2 piece drive shaft with a one piece. This reduced the amount of angle change as the truck was loaded. They also added a shim to increase the drive angle. Problem solved.



My '98 has a minor launch shudder when at max GVW, but not enough to do anything about. Just ease of the power a little and it goes away.

 

[mbrolin]

Id find a quality alignment shop. By doing a computerized 4 wheel alignment the thrust angle can be measured. This should not be more than 1-2 degs. The thrust angle is the angle of the rearend for and aft in comparison to the front. Basically an expensive tape measuremnt but acceptable in court as evidence.

 

[mikel]

When I got my '01 I was surprised to see a two piece driveshaft since my '99 auto had a one piece. Does anyone know the logic behind using a two piece instead of a one piece driveshaft?



Mike

 

[MidwestMotorman]

two piece vs single

The two piece setup allows the use of three ujoints. This eases the stress of using a one piece shaft with two ujoints. You can have more loading of the frame/suspension and more flexibility without drivetrain bind. You have to use a carrier bearing to center the two piece shaft, and one has to make sure the carrier is correctly placed (the driveshaft will want to wiggle around due to the flexibility, like a jump rope sags when swung), and that the carrier bearing is firm enough to dampen vibrations and not egg out.



Lots of trucks had two piece driveshafts years ago, but the driveshafts were really small (smaller around) and lighter (my 67 D300 has a 2" wide driveshaft with dinky ujoints). If the smaller shafts were out of balance, you did not notice it as much, and they did not flop around as bad either. Our rams have such large shafts that they must be fine balanced and held firmly, which obviously D-C has not done carefully. Sfiff heavy ujoints contribute to the sag in motion, like my jump rope example, because they can have limits in flexibility. The greater the original angle of the two piece shaft, the more wobble the shaft can have. 4x4's have more angle than the 2wd trucks, and therefore more chance for vibration.



So, by the nature of the beast, a two piece driveshaft can have more vibration present.



Hope I helped, and did not mis-state anything.